@Article{ LeePLSK2013,
title = {A new method for estimating population receptive field topography in visual cortex},
journal = {NeuroImage},
year = {2013},
month = {5},
volume = {Epub ahead},
abstract = {We introduce a new method for measuring visual population receptive fields (pRF) with functional magnetic resonance imaging (fMRI). The pRF structure is modeled as a set of weights that can be estimated by solving a linear model that predicts the Blood Oxygen Level-Dependent (BOLD) signal using the stimulus protocol and the canonical hemodynamic response function. This method does not make a priori assumptions about the specific pRF shape and is therefore a useful tool for uncovering the underlying pRF structure at different spatial locations in an unbiased way. We show that our method is more accurate than a previously described method (Dumoulin and Wandell, 2008) which directly fits a 2-dimensional isotropic Gaussian pRF model to predict the fMRI time-series. We demonstrate that direct-fit models do not fully capture the actual pRF shape, and can be prone to pRF center mislocalization when the pRF is located near the border of the stimulus space. A quantitative comparison demonstrates that our method outperforms the direct-fit methods in the pRF center modeling by achieving higher explained variance of the BOLD signal. This was true for direct-fit isotropic Gaussian, anisotropic Gaussian, and difference of isotropic Gaussians model. Importantly, our model is also capable of exploring a variety of pRF properties such as surround suppression, receptive field center elongation, orientation, location and size. Additionally, the proposed method is particularly attractive for monitoring pRF properties in the visual areas of subjects with lesions of the visual pathways, where it is difficult to anticipate what shape the reorganized pRF might take. Finally, the method proposed here is more efficient in computation time than direct-fit methods, which need to search for a set of parameters in an extremely large searching space. Instead, this method uses the pRF topography to constrain the space that needs to be searched for the subsequent modeling.},
web_url = {http://www.sciencedirect.com/science/article/pii/S105381191300520X},
state = {published},
DOI = {10.1016/j.neuroimage.2013.05.026},
author = {Lee S{slee}{Department Physiology of Cognitive Processes}, Papanikolaou A{amalia}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Smirnakis SM and Keliris GA{george}{Department Physiology of Cognitive Processes}}
}

@Article{ KapoorKKLP2013,
title = {Development of Tube Tetrodes and a Multi-Tetrode Drive for deep structure electrophysiological recordings in the macaque brain},
journal = {Journal of Neuroscience Methods},
year = {2013},
month = {5},
volume = {216},
number = {1},
pages = {43–48},
abstract = {Understanding the principles that underlie information processing by neuronal networks requires simultaneous recordings from large populations of well isolated single units. Twisted wire tetrodes (TWTs), typically made by winding together four ultrathin wires (diameter–12 to 25 microns), are ideally suited for such population recordings. They are advantageous over single electrodes; both with respect to quality of isolation as well as the number of single units isolated and have therefore been used extensively for superficial cortical recordings. However, their limited tensile strength poses a difficulty to their use for recordings in deep brain areas. We therefore developed a method to overcome this limitation and utilize tetrodes for electrophysiological recordings in the inferotemporal cortex of rhesus macaque. We fabricated a novel, stiff tetrode called the tube tetrode (TuTe) and developed a multi-tetrode driving system for advancing up to 5 TuTes through a ball and socket chamber to precise locations in the temporal lobe of a rhesus macaque. The signal quality acquired with TuTes was comparable to conventional TWTs and allowed excellent isolation of multiple single units. We describe here a simple method for constructing TuTes, which requires only standard laboratory equipment. Further, our TuTes can be easily adapted to work with other microdrives commonly used for electrophysiological investigation in the macaque brain and produce minimal damage to the cortex along its path because of their ultrathin diameter. The tetrode development described here could allow studying neuronal populations in deep lying brain structures previously difficult to reach with the current technology.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0165027013001222},
state = {published},
DOI = {10.1016/j.jneumeth.2013.03.017},
author = {Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Krampe E{krampe}{Department Physiology of Cognitive Processes}, Klug A{klug}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panagiotaropoulos TI{theofanis}{Department Physiology of Cognitive Processes}}
}

@Article{ OmerHG2013,
title = {Temporally- structured acquisition of multidimensional optical imaging data facilitates visualization of elusive cortical representations in the behaving monkey},
journal = {NeuroImage},
year = {2013},
month = {5},
volume = {Epub ahead},
abstract = {Fundamental understanding of higher cognitive functions can greatly benefit from imaging of cortical activity with high spatiotemporal resolution in the behaving non-human primate.To achieve rapid imaging of high-resolution dynamicsof cortical representations of spontaneous and evoked activity ,we designed a novel data acquisition protocol for sensory stimulation by rapidly interleaving multiple stimuli in continuous sessions of optical imaging with voltage-sensitive dyes. We also tested a new algorithm for the “temporally structured componentanalysis” (TSCA) of a multidimensional timeseries that was developed for our new data acquisitionprotocol, but was tested only on simulated data (Blumenfeld, 2010). In addition to the raw data, the algorithm incorporates prior knowledge about the temporal structure of the data as well as input from other information. Here we showed thatTSCA can successfully separate functional signal components from other signals referred to as noise. Imaging of responses to multiple visual stimuli, utilizing voltage-sensitive dyes, wasperformed on the visual cortex of awake monkeys. Multiple cortical representations,including orientation and ocular dominance maps as well as thehitherto elusive retinotopic representation of orientation stimuli, were extracted in only 10 secondsof imaging, approximately two orders of magnitude faster than accomplished by conventional methods. Since the approach is rather general, other imaging techniques may also benefit from the same stimulation protocol. This methodology can thus facilitate rapid optical imaging explorations in monkeys, rodents and other specieswith a versatility and speed that were not feasible before.},
web_url = {http://www.sciencedirect.com/science/article/pii/S1053811913005399},
state = {published},
DOI = {10.1016/j.neuroimage.2013.05.045},
author = {Omer DB{domer}{Department Physiology of Cognitive Processes}, Hildesheim R and Grinvald A}
}

@Article{ HagbergMPBMVKDKL2013,
title = {Diffusion properties of conventional and calcium sensitive MRI contrast agents in the rat cerebral cortex},
journal = {Contrast Media and Molecular Imaging},
year = {2013},
month = {3},
state = {accepted},
author = {Hagberg G{ghagberg}{Department High-Field Magnetic Resonance}, Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, Power A{apower}{Department Physiology of Cognitive Processes}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Merkle H{hellmut}, Valerij G, Kiseleyd V, Dhingra K{kirti}{Department Physiology of Cognitive Processes}, Kubičeke V and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ NgLK2012,
title = {EEG phase patterns reflect the selectivity of neural firing},
journal = {Cerebral Cortex},
year = {2013},
month = {2},
volume = {23},
number = {2},
pages = {389-398},
abstract = {Oscillations are pervasive in encephalographic signals and supposedly reflect cognitive processes and sensory representations. While the relation between oscillation amplitude (power) and sensory–cognitive variables has been extensively studied, recent work reveals that the dynamic oscillation signature (phase pattern) can carry information about such processes to a greater degree than amplitude. To elucidate the neural correlates of oscillatory phase patterns, we compared the stimulus selectivity of neural firing rates and auditory-driven electroencephalogram (EEG) oscillations. We employed the same naturalistic sound stimuli in 2 experiments, one recording scalp EEGs in humans and one recording intracortical local field potentials (LFPs) and single neurons in macaque auditory cortex. Using stimulus decoding techniques, we show that stimulus selective firing patterns imprint on the phase rather than the amplitude of slow (theta band) oscillations in LFPs and EEG. In particular, we find that stimuli which can be discriminated by firing rates can also be discriminated by phase patterns but not by oscillation amplitude and that stimulus-specific phase patterns also persist in the absence of increases of oscillation power. These findings support a neural basis for stimulus selective and entrained EEG phase patterns and reveal a level of interrelation between encephalographic signals and neural firing beyond simple amplitude covariations in both signals.},
web_url = {http://cercor.oxfordjournals.org/content/23/2/389.full.pdf+html},
state = {published},
DOI = {10.1093/cercor/bhs031},
author = {Ng BSW{benedict}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ VibhuteEVMLA2012,
title = {Synthesis and characterization of pH-sensitive, biotinylated MRI contrast agents and their conjugates with avidin},
journal = {Organic & Biomolecular Chemistry},
year = {2013},
month = {2},
volume = {11},
number = {8},
pages = {1294-1305},
abstract = {Responsive or smart contrast agents (SCAs) provide new opportunities in magnetic resonance imaging (MRI) to examine a number of physiological and pathological events. However, their application in vivo remains challenging. Therefore, much research is focused on the optimization of their properties, to enable their use in additional imaging modalities, pre-targeted delivery, or to increase the local concentration of the agent. The key feature in the SCA synthetic modification is the retention of their physicochemical properties related to the specific MR response. Here, we report the preparation and characterization of pH sensitive SCAs appended with a phosphonate pendant arm and either an aliphatic (GdL1) or aromatic linker (GdL2). The longitudinal relaxivity of GdL1 and GdL2 increases by 146% and 31%, respectively, while the pH decreases from 9 to 5. These two SCAs were converted to the biotinylated systems GdL3 and GdL4 and their interaction with avidin was investigated. The binding affinity with avidin was assessed with a fluorescence displacement assay and with MRI phantom experiments in a 3T MRI scanner. The fluorometric assay and MRI E-titrations revealed a 3 : 1 binding mode of GdL3–4 to avidin with the binding affinity as high as that of the parent avidin–biotin complex. The high binding affinity was confirmed with MRI by a competitive assay. The avidin–GdL3–4 complexes thus obtained exhibit changes in both r1 and r2 that are pH dependent. The results reveal a new pathway for the modification and improvement of SCAs to make them more suitable for in vivo application.},
web_url = {http://pubs.rsc.org/en/content/articlepdf/2013/ob/c2ob26555a},
state = {published},
DOI = {10.1039/C2OB26555A},
author = {Vibhute SM{svibhute}{Department Physiology of Cognitive Processes}, Engelmann J{joern}{Department High-Field Magnetic Resonance}, Verbić T, Maier ME, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Angelovski G{goran}{Department Physiology of Cognitive Processes}}
}

@Article{ PanagiotaropoulosKLD2013,
title = {A Common Neurodynamical Mechanism Could Mediate Externally Induced and Intrinsically Generated Transitions in Visual Awareness},
journal = {PLoS ONE},
year = {2013},
month = {1},
volume = {8},
number = {1},
pages = {1-10},
abstract = {The neural correlates of conscious visual perception are commonly studied in paradigms of perceptual multistability that allow multiple perceptual interpretations during unchanged sensory stimulation. What is the source of this multistability in the content of perception? From a theoretical perspective, a fine balance between deterministic and stochastic forces has been suggested to underlie the spontaneous, intrinsically driven perceptual transitions observed during multistable perception. Deterministic forces are represented by adaptation of feature-selective neuronal populations encoding the competing percepts while stochastic forces are modeled as noise-driven processes. Here, we used a unified neuronal competition model to study the dynamics of adaptation and noise processes in binocular flash suppression (BFS), a form of externally induced perceptual suppression, and compare it with the dynamics of intrinsically driven alternations in binocular rivalry (BR). For the first time, we use electrophysiological, biologically relevant data to constrain a model of perceptual rivalry. Specifically, we show that the mean population discharge pattern of a perceptually modulated neuronal population detected in electrophysiological recordings in the lateral prefrontal cortex (LPFC) during BFS, constrains the dynamical range of externally induced perceptual transitions to a region around the bifurcation separating a noise-driven attractor regime from an adaptation-driven oscillatory regime. Most interestingly, the dynamical range of intrinsically driven perceptual transitions during BR is located in the noise-driven attractor regime, where it overlaps with BFS. Our results suggest that the neurodynamical mechanisms of externally induced and spontaneously generated perceptual alternations overlap in a narrow, noise-driven region just before a bifurcation where the system becomes adaptation-driven.},
web_url = {http://www.plosone.org/article/fetchObjectAttachment.action;jsessionid=EF29256D0A77BD57133469DBE40B96AA?uri=info%3Adoi%2F10.1371%2Fjournal.pone.0053833&representation=PDF},
state = {published},
DOI = {10.1371/journal.pone.0053833},
EPUB = {e53833},
author = {Panagiotaropoulos TI{theofanis}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Deco G}
}

@Article{ PawlakGSGK2013,
title = {Changing the responses of cortical neurons from sub- to suprathreshold using single spikes in vivo},
journal = {eLife},
year = {2013},
month = {1},
volume = {2},
pages = {1-18},
abstract = {Action Potential (APs) patterns of sensory cortex neurons encode a variety of stimulus features, but how can a neuron change the feature to which it responds? Here, we show that in vivo a spike-timing-dependent plasticity (STDP) protocol—consisting of pairing a postsynaptic AP with visually driven presynaptic inputs—modifies a neurons' AP-response in a bidirectional way that depends on the relative AP-timing during pairing. Whereas postsynaptic APs repeatedly following presynaptic activation can convert subthreshold into suprathreshold responses, APs repeatedly preceding presynaptic activation reduce AP responses to visual stimulation. These changes were paralleled by restructuring of the neurons response to surround stimulus locations and membrane-potential time-course. Computational simulations could reproduce the observed subthreshold voltage changes only when presynaptic temporal jitter was included. Together this shows that STDP rules can modify output patterns of sensory neurons and the timing of single-APs plays a crucial role in sensory coding and plasticity.},
web_url = {http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3552422/pdf/elife00012.pdf},
state = {published},
DOI = {10.7554/eLife.00012},
EPUB = {e00012},
author = {Pawlak V{vpawlak}{Research Group Neural Population Imaging}, Greenberg DS{david}{Research Group Neural Population Imaging}, Sprekeler H, Gerstner W and Kerr JND{jkerr}{Research Group Neural Population Imaging}}
}

@Article{ SchindlerB2012,
title = {Parietal Cortex Codes for Egocentric Space beyond the Field of View},
journal = {Current Biology},
year = {2013},
month = {1},
volume = {23},
number = {2},
pages = {177–182},
abstract = {Our subjective experience links covert visual and egocentric spatial attention seamlessly. However, the latter can extend beyond the visual field, covering all directions relative to our body. In contrast to visual representations [1, 2, 3 and 4], little is known about unseen egocentric representations in the healthy brain. Parietal cortex appears to be involved in both, because lesions in it can lead to deficits in visual attention, but also to a disorder of egocentric spatial awareness, known as hemispatial neglect [5 and 6]. Here, we used a novel virtual reality paradigm to probe our participants’ egocentric surrounding during fMRI recordings. We found that egocentric unseen space was represented by patterns of voxel activity in parietal cortex, independent of visual information. Intriguingly, the best decoding performances corresponded to brain areas associated with visual covert attention and reaching, as well as to lesion sites associated with spatial neglect.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0960982212014406},
state = {published},
DOI = {10.1016/j.cub.2012.11.060},
author = {Schindler A{aschindler}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Article{ ZaretskayaAB2012,
title = {Parietal Cortex Mediates Conscious Perception of Illusory Gestalt},
journal = {Journal of Neuroscience},
year = {2013},
month = {1},
volume = {33},
number = {2},
pages = {523-531},
abstract = {Grouping local elements into a holistic percept, also known as spatial binding, is crucial for meaningful perception. Previous studies have shown that neurons in early visual areas V1 and V2 can signal complex grouping-related information, such as illusory contours or object-border ownerships. However, relatively little is known about higher-level processes contributing to these signals and mediating global Gestalt perception. We used a novel bistable motion illusion that induced alternating and mutually exclusive vivid conscious experiences of either dynamic illusory contours forming a global Gestalt or moving ungrouped local elements while the visual stimulation remained the same. fMRI in healthy human volunteers revealed that activity fluctuations in two sites of the parietal cortex, the superior parietal lobe and the anterior intraparietal sulcus (aIPS), correlated specifically with the perception of the grouped illusory Gestalt as opposed to perception of ungrouped local elements. We then disturbed activity at these two sites in the same participants using transcranial magnetic stimulation (TMS). TMS over aIPS led to a selective shortening of the duration of the global Gestalt percept, with no effect on that of local elements. The results suggest that aIPS activity is directly involved in the process of spatial binding during effortless viewing in the healthy brain. Conscious perception of global Gestalt is therefore associated with aIPS function, similar to attention and perceptual selection.},
web_url = {http://www.jneurosci.org/content/33/2/523.full.pdf+html},
state = {published},
DOI = {10.1523/​JNEUROSCI.2905-12.2013},
author = {Zaretskaya N{nataliya}{Department Physiology of Cognitive Processes}, Anstis S and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ BarbieriMLPB2013,
title = {Input dependence of local field potential spectra: experiment vs theory},
year = {2013},
month = {3},
number = {I-30},
web_url = {http://www.cosyne.org/c/index.php?title=Cosyne_13},
event_name = {Computational and Systems Neuroscience Meeting (COSYNE 2013)},
event_place = {Salt Lake City, UT, USA},
state = {published},
author = {Barbieri F, Mazzoni A, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Panzeri S{stefano} and Brunel N}
}

@Poster{ BiessmannGMZRLMR2013,
title = {Investigating neurovascular coupling using canonical correlation analysis between pharmacological MRI and electrophysiology},
journal = {BMC Neuroscience},
year = {2013},
volume = {10},
number = {Suppl 1},
pages = {P86},
abstract = {Despite its young age, functional Magnetic Resonance Imaging (fMRI) has become one of the most popular brain imaging techniques. However, the relationship between brain activity and the blood oxygen level dependent (BOLD) contrast as measured with fMRI, the so called neurovascular coupling, is not yet fully understood. One possibility of experimentally manipulating the neurovascular coupling mechanisms is administration of vaso-active and neuro-active substances, such as Acetylcholine (ACh). Combining those pharmacological interventions with simultaneous measurements of electrophysiological and BOLD response allows for deeper insights in the dependencies between neural and hemodynamic response to sensory stimulation.

We developed a method based on kernel canonical correlation analysis that is able to deal with the high dimensionality of the fMRI signal while exploiting the high temporal resolution of the electrophysiology. The algorithm finds filters for fMRI and electrophysiological data that maximize the crosscorrelation between the two data sources. Projecting the data onto those filters allows to compute a crosscorrelation function between fMRI and electrophysiological data that reflects the coupling between neural and hemodynamic response. We present data recorded in primary visual cortex of the non-human primate during a visual stimulation paradigm and local application of ACh. Comparing the neurovascular crosscorrellograms after local injections of ACh and with those from control conditions, we find that the coupling is dramatically affected by ACh. In particular, the extent to which the stimulus is reflected in the crosscorrelation function is decreased under influence of ACh. Inspection of the spatial filters of the BOLD response shows that this change is primarily accounted for by cholinergic effects on voxels around the injection site. The filters computed for the neurophysiological data suggest that it is mainly neural activity in the alpha and gamma band that contributes to the change in coupling.
In summary, the results provide preliminary evidence for a change in neurovascular coupling induced by high levels of ACh. The voxel patterns (for fMRI data) and patterns in the time-frequency domain (for electrophysiological data) that give rise to this change can be revealed using a novel analysis method.},
web_url = {http://www.biomedcentral.com/1471-2202/10/S1/P86},
event_name = {Eighteenth Annual Computational Neuroscience Meeting (CNS*2009)},
event_place = {Berlin, Germany},
state = {published},
DOI = {10.1186/1471-2202-10-S1-P86},
author = {Biessmann F{fbiessma}{Department Physiology of Cognitive Processes}, Gretton A{arthur}{Department Empirical Inference}, Meinecke FC, Zhang X{xiaozhe}{Department Physiology of Cognitive Processes}, Rainer G{gregor}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, M\"uller K-R{klaus}{Department Empirical Inference} and Rauch A{arauch}{Department Physiology of Cognitive Processes}}
}

@Article{ MusallvRLW2012,
title = {Effects of neural synchrony on surface EEG},
journal = {Cerebral Cortex},
year = {2012},
month = {12},
volume = {Epub ahead},
abstract = {It has long been assumed that the surface electroencephalography (EEG) signal depends on both the amplitude and spatial synchronization of underlying neural activity, though isolating their respective contribution remains elusive. To address this, we made simultaneous surface EEG measurements along with intracortical recordings of local field potentials (LFPs) in the primary visual cortex of behaving nonhuman primates. We found that trial-by-trial fluctuations in EEG power could be explained by a linear combination of LFP power and interelectrode temporal synchrony. This effect was observed in both stimulus and stimulus-free conditions and was particularly strong in the gamma range (30–100 Hz). Subsequently, we used pharmacological manipulations to show that neural synchrony can produce a positively modulated EEG signal even when the LFP signal is negatively modulated. Taken together, our results demonstrate that neural synchrony can modulate EEG signals independently of amplitude changes in neural activity. This finding has strong implications for the interpretation of EEG in basic and clinical research, and helps reconcile EEG response discrepancies observed in different modalities (e.g., EEG vs. functional magnetic resonance imaging) and different spatial scales (e.g., EEG vs. intracranial EEG).},
web_url = {http://cercor.oxfordjournals.org/content/early/2012/12/12/cercor.bhs389.full.pdf+html},
state = {published},
DOI = {10.1093/cercor/bhs389},
author = {Musall S{unone}{Department Physiology of Cognitive Processes}, von Pf\"ostl V{vpfoestl}{Department Physiology of Cognitive Processes}, Rauch A{arauch}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Whittingstall K{kevin}{Department Physiology of Cognitive Processes}}
}

@Article{ TuressonLH2012,
title = {Category-selective phase coding in the superior temporal sulcus},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
year = {2012},
month = {11},
volume = {109},
number = {47},
pages = {19438-19443},
abstract = {Object perception and categorization can occur so rapidly that behavioral responses precede or co-occur with the firing rate changes in the object-selective neocortex. Phase coding could, in principle, support rapid representation of object categories, whereby the first spikes evoked by a stimulus would appear at different phases of an oscillation, depending on the object category. To determine whether object-selective regions of the neo-cortex demonstrate phase coding, we presented images of faces and objects to two monkeys while recording local field potentials (LFP) and single unit activity from object-selective regions in the upper bank superior temporal sulcus. Single units showed preferred phases of firing that depended on stimulus category, emerging with the initiation of spiking responses after stimulus onset. Differences in phase of firing were seen below 20 Hz and in the gamma and high-gamma frequency ranges. For all but the <20-Hz cluster, phase differences remained category-specific even when controlling for stimulus-locked activity, revealing that phase-specific firing is not a simple consequence of category-specific differences in the evoked responses of the LFP. In addition, we tested for firing rate-to-phase conversion. Category-specific differences in firing rates accounted for 30–40% of the explained variance in phase occurring at lower frequencies (<20 Hz) during the initial response, but was limited (<20% of the explained variance) in the 30- to 60-Hz frequency range, suggesting that gamma phase-of-firing effects reflect more than evoked LFP and firing rate responses. The present results are consistent with theoretical models of rapid object processing and extend previous observations of phase coding to include object-selective neocortex.},
web_url = {http://www.pnas.org/content/109/47/19438},
state = {published},
DOI = {10.1073/pnas.1217012109},
author = {Turesson HK{hjalmar}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Hoffman KL{kari}{Department Physiology of Cognitive Processes}}
}

@Article{ GoenseML2012_2,
title = {High-Resolution fMRI Reveals Laminar Differences in Neurovascular Coupling between Positive and Negative BOLD Responses},
journal = {Neuron},
year = {2012},
month = {11},
volume = {76},
number = {3},
pages = {629–639},
abstract = {The six cortical layers have distinct anatomical and physiological properties, like different energy use and different feedforward and feedback connectivity. It is not known if and how layer-specific neural processes are reflected in the fMRI signal. To address this question we used high-resolution fMRI to measure BOLD, CBV, and CBF responses to stimuli that elicit positive and negative BOLD signals in macaque primary visual cortex. We found that regions with positive BOLD responses had parallel increases in CBV and CBF, whereas areas with negative BOLD responses showed a decrease in CBF but an increase in CBV. For positive BOLD responses, CBF and CBV increased in the center of the cortex, but for negative BOLD responses, CBF decreased superficially while CBV increased in the center. Our findings suggest different mechanisms for neurovascular coupling for BOLD increases and decreases, as well as laminar differences in neurovascular coupling.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0896627312008549},
state = {published},
DOI = {10.1016/j.neuron.2012.09.019},
author = {Goense J{jozien}{Department Physiology of Cognitive Processes}, Merkle H{hellmut} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ LogothetisEMASEBO2012,
title = {Hippocampal-cortical interaction during periods of subcortical silence},
journal = {Nature},
year = {2012},
month = {11},
volume = {491},
number = {7425},
pages = {547–553},
abstract = {Hippocampal ripples, episodic high-frequency field-potential oscillations primarily occurring during sleep and calmness, have been described in mice, rats, rabbits, monkeys and humans, and so far they have been associated with retention of previously acquired awake experience. Although hippocampal ripples have been studied in detail using neurophysiological methods, the global effects of ripples on the entire brain remain elusive, primarily owing to a lack of methodologies permitting concurrent hippocampal recordings and whole-brain activity mapping. By combining electrophysiological recordings in hippocampus with ripple-triggered functional magnetic resonance imaging, here we show that most of the cerebral cortex is selectively activated during the ripples, whereas most diencephalic, midbrain and brainstem regions are strongly and consistently inhibited. Analysis of regional temporal response patterns indicates that thalamic activity suppression precedes the hippocampal population burst, which itself is temporally bounded by massive activations of association and primary cortical areas. These findings suggest that during off-line memory consolidation, synergistic thalamocortical activity may be orchestrating a privileged interaction state between hippocampus and cortex by silencing the output of subcortical centres involved in sensory processing or potentially mediating procedural learning. Such a mechanism would cause minimal interference, enabling consolidation of hippocampus-dependent memory.},
web_url = {http://www.nature.com/nature/journal/v491/n7425/full/nature11618.html},
state = {published},
DOI = {10.1038/nature11618},
author = {Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Augath M{mark}{Department Physiology of Cognitive Processes}, Steudel T{steudel}{Department Physiology of Cognitive Processes}, Evrard HC{evrard}{Department Physiology of Cognitive Processes}, Besserve M{besserve}{Department Physiology of Cognitive Processes} and Oeltermann A{axel}}
}

@Article{ KayserIP2012,
title = {Analysis of slow (theta) oscillations as a potential temporal reference frame for information coding in sensory cortices},
journal = {PLoS Computational Biology},
year = {2012},
month = {10},
volume = {8},
number = {10},
pages = {1-13},
abstract = {While sensory neurons carry behaviorally relevant information in responses that often extend over hundreds of milliseconds, the key units of neural information likely consist of much shorter and temporally precise spike patterns. The mechanisms and temporal reference frames by which sensory networks partition responses into these shorter units of information remain unknown. One hypothesis holds that slow oscillations provide a network-intrinsic reference to temporally partitioned spike trains without exploiting the millisecond-precise alignment of spikes to sensory stimuli. We tested this hypothesis on neural responses recorded in visual and auditory cortices of macaque monkeys in response to natural stimuli. Comparing different schemes for response partitioning revealed that theta band oscillations provide a temporal reference that permits extracting significantly more information than can be obtained from spike counts, and sometimes almost as much information as obtained by partitioning spike trains using precisely stimulus-locked time bins. We further tested the robustness of these partitioning schemes to temporal uncertainty in the decoding process and to noise in the sensory input. This revealed that partitioning using an oscillatory reference provides greater robustness than partitioning using precisely stimulus-locked time bins. Overall, these results provide a computational proof of concept for the hypothesis that slow rhythmic network activity may serve as internal reference frame for information coding in sensory cortices and they foster the notion that slow oscillations serve as key elements for the computations underlying perception.},
web_url = {http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1002717},
state = {published},
DOI = {10.1371/journal.pcbi.1002717},
EPUB = {e1002717},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Ince RAA{rince}{Department Physiology of Cognitive Processes}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Article{ vanGrootelvv2012,
title = {Experimental test of spatial updating models for monkey eye-head gaze shifts},
journal = {PLoS ONE},
year = {2012},
month = {10},
volume = {7},
number = {10},
pages = {1-18},
abstract = {How the brain maintains an accurate and stable representation of visual target locations despite the occurrence of saccadic gaze shifts is a classical problem in oculomotor research. Here we test and dissociate the predictions of different conceptual models for head-unrestrained gaze-localization behavior of macaque monkeys. We adopted the double-step paradigm with rapid eye-head gaze shifts to measure localization accuracy in response to flashed visual stimuli in darkness. We presented the second target flash either before (static), or during (dynamic) the first gaze displacement. In the dynamic case the brief visual flash induced a small retinal streak of up to about 20 deg at an unpredictable moment and retinal location during the eye-head gaze shift, which provides serious challenges for the gaze-control system. However, for both stimulus conditions, monkeys localized the flashed targets with accurate gaze shifts, which rules out several models of visuomotor control. First, these findings exclude the possibility that gaze-shift programming relies on retinal inputs only. Instead, they support the notion that accurate eye-head motor feedback updates the gaze-saccade coordinates. Second, in dynamic trials the visuomotor system cannot rely on the coordinates of the planned first eye-head saccade either, which rules out remapping on the basis of a predictive corollary gaze-displacement signal. Finally, because gaze-related head movements were also goal-directed, requiring continuous access to eye-in-head position, we propose that our results best support a dynamic feedback scheme for spatial updating in which visuomotor control incorporates accurate signals about instantaneous eye- and head positions rather than relative eye- and head displacements.},
web_url = {http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0047606},
state = {published},
DOI = {10.1371/journal.pone.0047606},
EPUB = {e47606},
author = {van Grootel TJ{vangrootel}{Department Physiology of Cognitive Processes}, van der Willigen RF and van Opstal AJ}
}

@Article{ InceMBLP2011,
title = {A novel test to determine the significance of neural selectivity to single and multiple potentially correlated stimulus features},
journal = {Journal of Neuroscience Methods},
year = {2012},
month = {9},
volume = {210},
number = {1},
pages = {49–65},
abstract = {Mutual information is a principled non-linear measure of dependence between stochastic variables, which is widely used to study the selectivity of neural responses to external stimuli. Here we define and develop a set of novel statistical independence tests based on mutual information, which quantify the significance of neural selectivity to either single features or to multiple, potentially correlated stimulus features like those often present in naturalistic stimuli. If the values of different features are correlated during stimulus presentation, it is difficult to establish if one feature is genuinely encoded by the response, or if it instead appears to be encoded only as a side effect of its correlation with another genuinely represented feature. Our tests provide a way to disambiguate between these two possibilities. We use realistic simulations of neural responses tuned to one or more correlated stimulus features to investigate how limited sampling bias correction procedures affect the statistical power of such independence tests, and we characterize the regimes in which the distribution of information values under the null hypothesis can be approximated by simple distributions (Chi-square or Gaussian). Finally, we apply these tests to experimental data to determine the significance of tuning of the band limited power (BLP) of the gamma [30–100 Hz] frequency range of the primary visual cortical local field potential to multiple correlated features during presentation of naturalistic movies. We show that gamma BLP carries significant, genuine information about orientation, space contrast and time contrast, despite the strong correlations between these features.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0165027011006893},
state = {published},
DOI = {10.1016/j.jneumeth.2011.11.013},
author = {Ince RAA{rince}{Department Physiology of Cognitive Processes}{Department Physiology of Cognitive Processes}, Mazzoni A, Bartels A{abartels}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Article{ KelirisMHLSE2012,
title = {A smart 19F and 1H MRI probe with self-immolative linker as a versatile tool for detection of enzymes},
journal = {Contrast Media and Molecular Imaging},
year = {2012},
month = {9},
volume = {7},
number = {5},
pages = {478–483},
abstract = {Here we report on a dual-modal 19F and 1H MRI paramagnetic probe with a self-immolative linker, Gd–DOMF–Gal. The enzymatic conversion of this probe by β-galactosidase resulted in a simultaneous turning on of the fluorine signal and changed ability of the Gd3+ complex to modulate the 1H MR signal intensity of the surrounding water molecules. A versatile imaging platform for monitoring a variety of enzymes by 19F and 1H MRI using this molecular design is proposed.},
web_url = {http://onlinelibrary.wiley.com/doi/10.1002/cmmi.1470/pdf},
state = {published},
DOI = {10.1002/cmmi.1470},
author = {Keliris A{abrud}{Department High-Field Magnetic Resonance}, Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, Hagberg GE{ghagberg}{Department High-Field Magnetic Resonance}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Scheffler K{scheffler}{Department High-Field Magnetic Resonance} and Engelmann J{joern}{Department High-Field Magnetic Resonance}}
}

@Article{ GleissK2012,
title = {Audio-visual detection benefits in the rat},
journal = {PLoS ONE},
year = {2012},
month = {9},
volume = {7},
number = {9},
pages = {1-8},
abstract = {Human psychophysical studies have described multisensory perceptual benefits such as enhanced detection rates and faster reaction times in great detail. However, the neural circuits and mechanism underlying multisensory integration remain difficult to study in the primate brain. While rodents offer the advantage of a range of experimental methodologies to study the neural basis of multisensory processing, rodent studies are still limited due to the small number of available multisensory protocols. We here demonstrate the feasibility of an audio-visual stimulus detection task for rats, in which the animals detect lateralized uni- and multi-sensory stimuli in a two-response forced choice paradigm. We show that animals reliably learn and perform this task. Reaction times were significantly faster and behavioral performance levels higher in multisensory compared to unisensory conditions. This benefit was strongest for dim visual targets, in agreement with classical patterns of multisensory integration, and was specific to task-informative sounds, while uninformative sounds speeded reaction times with little costs for detection performance. Importantly, multisensory benefits for stimulus detection and reaction times appeared at different levels of task proficiency and training experience, suggesting distinct mechanisms inducing these two multisensory benefits. Our results demonstrate behavioral multisensory enhancement in rats in analogy to behavioral patterns known from other species, such as humans. In addition, our paradigm enriches the set of behavioral tasks on which future studies can rely, for example to combine behavioral measurements with imaging or pharmacological studies in the behaving animal or to study changes of integration properties in disease models.},
web_url = {http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0045677},
state = {published},
DOI = {10.1371/journal.pone.0045677},
EPUB = {e45677},
author = {Gleiss S{sgleiss}{Research Group Physiology of Sensory Integration} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ SchindlerHB2012,
title = {Coding of Melodic Gestalt in Human Auditory Cortex},
journal = {Cerebral Cortex},
year = {2012},
month = {9},
volume = {Epub ahead},
abstract = {The perception of a melody is invariant to the absolute properties of its constituting notes, but depends on the relation between them—the melody's relative pitch profile. In fact, a melody's “Gestalt” is recognized regardless of the instrument or key used to play it. Pitch processing in general is assumed to occur at the level of the auditory cortex. However, it is unknown whether early auditory regions are able to encode pitch sequences integrated over time (i.e., melodies) and whether the resulting representations are invariant to specific keys. Here, we presented participants different melodies composed of the same 4 harmonic pitches during functional magnetic resonance imaging recordings. Additionally, we played the same melodies transposed in different keys and on different instruments. We found that melodies were invariantly represented by their blood oxygen level–dependent activation patterns in primary and secondary auditory cortices across instruments, and also across keys. Our findings extend common hierarchical models of auditory processing by showing that melodies are encoded independent of absolute pitch and based on their relative pitch profile as early as the primary auditory cortex.},
web_url = {http://cercor.oxfordjournals.org/content/early/2012/09/16/cercor.bhs289.full.pdf+html},
state = {published},
DOI = {10.1093/cercor/bhs289},
author = {Schindler A{aschindler}{Department Physiology of Cognitive Processes}, Herdener M{herdener}{Department High-Field Magnetic Resonance} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Article{ MaierPTK2012,
title = {Introduction to research topic – binocular rivalry: a gateway to studying consciousness},
journal = {Frontiers in Human Neuroscience},
year = {2012},
month = {9},
volume = {6},
number = {263},
pages = {1-3},
abstract = {In 1593, Neapolitan polymath Giambattista della Porta publicly lamented that he was unable to improve his impressive productivity (he had published in areas as diverse as cryptography, hydraulics, pharmacology, optics, and classic fiction). Della Porta was trying to read two books simultaneously by placing both volumes side-by-side, and using each eye independently. To his great surprise, his setup allowed him to only read one book at a time. This discovery arguably marks the first written account of binocular rivalry (Wade, 2000) – a perceptual phenomenon that more than 400 years later still both serves to intrigue as well as to illuminate the limits of scientific knowledge. At first glance, binocular rivalry is an oddball. In every day vision, our eyes receive largely matching views of the world. The brain combines the two images into a cohesive scene, and concurrently, perception is stable. However, when showing two very different images (such as two different books) to each eye, the brain resolves the conflict by adopting a “diplomatic” strategy. Rather than mixing the views of the two eyes into an insensible visual percept, observers perceive a dynamically changing series of perceptual snapshots, with one eye’s view dominating for a few seconds before being replaced by its rival from the other eye. With prolonged viewing of a rivalrous stimulus, one inevitably experiences a sequence of subjective perceptual reversals, separated by random time intervals, and this process continues for as long as the sensory conflict is present.},
web_url = {http://www.frontiersin.org/Human_Neuroscience/10.3389/fnhum.2012.00263/full},
state = {published},
DOI = {10.3389/fnhum.2012.00263},
author = {Maier A{amaier}{Department Physiology of Cognitive Processes}, Panagiotaropoulos TI{theofanis}{Department Physiology of Cognitive Processes}, Tsuchiya N and Keliris GA{george}{Department Physiology of Cognitive Processes}}
}

@Article{ DhingraVermaMEBML2012,
title = {Magnetic-Field-Dependent 1H Relaxivity Behavior of Biotin/Avidin-Based Magnetic Resonance Imaging Probes},
journal = {ChemPlusChem},
year = {2012},
month = {9},
volume = {77},
number = {9},
pages = {758–769},
abstract = {One major challenge in noninvasive mapping of various molecular targets is their inherently low in vivo concentration coupled with the insensitivity of imaging modalities, such as the widely used magnetic resonance imaging (MRI). Development of agents with high sensitivity and specificity is of paramount importance for structural and functional noninvasive imaging. The design, synthesis, and physiochemical characterization of two gadolinium-based contrast agents (CAs) for MRI, the sensitivity of which was optimized by exploiting the well-established biotin–avidin amplification strategies, are reported. The relaxivity of these agents showed a large increase if bound to avidin; specifically, the first compound showed an approximately 1000 % increase in transverse proton relaxivity (r2p), whereas the second compound had an approximately 250 % r2p increase. The increase in r2p was magnetic field independent in the range of 1.5–16.4 T whereas the longitudinal proton relaxivity (r1p) showed strong field dependence. The CAs were further characterized by measuring luminescence lifetimes and emission spectral changes upon addition of avidin to their Eu3+ analogues. The difference in relaxation rate behavior of both complexes was explained on the basis of hydration number modulation and the “global/internal motion concept”. The association constant of these CAs with avidin was found to be in the range of approximately 1015 M−1, which shows that the coupling of biotin to Gd-DO3A did not affect its affinity for binding to avidin (DO3A=1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid).},
web_url = {http://onlinelibrary.wiley.com/doi/10.1002/cplu.201200064/pdf},
state = {published},
DOI = {10.1002/cplu.201200064},
author = {Dhingra Verma K{kirti}{Department Physiology of Cognitive Processes}, Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Engelmann J{joern}{Department High-Field Magnetic Resonance}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Maier ME and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ MagriMLP2011,
title = {Optimal Band Separation of Extracellular Field Potentials},
journal = {Journal of Neuroscience Methods},
year = {2012},
month = {9},
volume = {210},
number = {1},
pages = {66–78},
abstract = {Local Field Potentials (LFPs) exhibit a broadband spectral structure that is traditionally partitioned into distinct frequency bands which are thought to originate from different types of neural events triggered by different processing pathways. However, the exact frequency boundaries of these processes are not known and, as a result, the frequency bands are often selected based on intuition, previous literature or visual inspection of the data. Here, we address these problems by developing a rigorous method for defining LFP frequency bands and their boundaries. The criterion introduced for determining the boundaries delimiting the bands is to maximize the information about an external correlate carried jointly by all bands in the partition. The method first partitions the LFP frequency range into two bands and then successively increases the number of bands in the partition. We applied the partitioning method to LFPs recorded from primary visual cortex of anaesthetized macaques, and we determined the optimal band partitioning that describes the encoding of naturalistic visual stimuli. The first optimal boundary partitioned the LFP response at 60 Hz into low and high frequencies, which had been previously found to convey independent information about the natural movie correlate. The second optimal boundary divided the high-frequency range at approximately 100 Hz into gamma and high-gamma frequencies, consistent with recent reports that these two bands reflect partly distinct neural processes. A third important boundary was at 25 Hz and it split the LFP range below 50 Hz into a stimulus-informative and a stimulus-independent band.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0165027011006613},
state = {published},
DOI = {10.1016/j.jneumeth.2011.11.005},
author = {Magri C{cmagri}{Department Physiology of Cognitive Processes}, Mazzoni A, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Article{ ErokhinBGCPRRSS2012,
title = {Stochastic hybrid 3D matrix: learning and adaptation of electrical properties},
journal = {Journal of Materials Chemistry},
year = {2012},
month = {9},
volume = {22},
number = {43},
pages = {22881-22887},
abstract = {Memristive devices are electronic elements with memory properties. This feature marks them out as possible candidates for mimicking synapse properties. Development of systems capable of performing simple brain operations demands a high level of integration of elements and their 3D organization into networks. Here, we demonstrate the formation and electrical properties of stochastic polymeric matrices. Several features of the network revealed similarities with those of the nervous system. In particular, applying different training protocols, we obtained two kinds of learning comparable to the “baby” and “adult” learning in animals and humans. To mimic “adult” learning, multi-task training was applied simultaneously resulting in the formation of few parallel pathways for a given task, modifiable by successive training. To mimic “baby” learning (imprinting), single task training was applied at one time, resulting in the formation of multiple parallel signal pathways, scarcely influenced by successive training.},
web_url = {http://pubs.rsc.org/en/content/articlepdf/2012/jm/c2jm35064e},
state = {published},
DOI = {10.1039/C2JM35064E},
author = {Erokhin V, Berzina T, Gorshkov K, Camorani P, Pucci A, Ricci L, Ruggeri G, Sigala R{sigala}{Department Physiology of Cognitive Processes} and Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}}
}

@Article{ BerensECMBT2012,
title = {A Fast and Simple Population Code for Orientation in Primate V1},
journal = {Journal of Neuroscience},
year = {2012},
month = {8},
volume = {32},
number = {31},
pages = {10618-10626},
abstract = {Orientation tuning has been a classic model for understanding single-neuron computation in the neocortex. However, little is known about how orientation can be read out from the activity of neural populations, in particular in alert animals. Our study is a first step toward that goal. We recorded from up to 20 well isolated single neurons in the primary visual cortex of alert macaques simultaneously and applied a simple, neurally plausible decoder to read out the population code. We focus on two questions: First, what are the time course and the timescale at which orientation can be read out from the population response? Second, how complex does the decoding mechanism in a downstream neuron have to be to reliably discriminate between visual stimuli with different orientations? We show that the neural ensembles in primary visual cortex of awake macaques represent orientation in a way that facilitates a fast and simple readout mechanism: With an average latency of 30–80 ms, the population code can be read out instantaneously with a short integration time of only tens of milliseconds, and neither stimulus contrast nor correlations need to be taken into account to compute the optimal synaptic weight pattern. Our study shows that—similar to the case of single-neuron computation—the representation of orientation in the spike patterns of neural populations can serve as an exemplary case for understanding the computations performed by neural ensembles underlying visual processing during behavior.},
web_url = {http://www.jneurosci.org/content/32/31/10618.full.pdf+html},
state = {published},
DOI = {10.1523/​JNEUROSCI.1335-12.2012},
author = {Berens P, Ecker AS{aecker}{Research Group Computational Vision and Neuroscience}, Cotton RJ, Ma WJ, Bethge M{mbethge}{Research Group Computational Vision and Neuroscience} and Tolias AS{atolias}{Department Physiology of Cognitive Processes}}
}

@Article{ NgSK2012,
title = {A precluding but not ensuring role of entrained low-frequency oscillations for auditory perception},
journal = {Journal of Neuroscience},
year = {2012},
month = {8},
volume = {32},
number = {35},
pages = {12268-12276},
abstract = {Oscillatory activity in sensory cortices reflects changes in local excitation–inhibition balance, and recent work suggests that phase signatures of ongoing oscillations predict the perceptual detection of subsequent stimuli. Low-frequency oscillations are also entrained by dynamic natural scenes, suggesting that the chance of detecting a brief target depends on the relative timing of this to the entrained rhythm. We tested this hypothesis in humans by implementing a cocktail-party-like scenario requiring subjects to detect a target embedded in a cacophony of background sounds. Using EEG to measure auditory cortical oscillations, we find that the chance of target detection systematically depends on both power and phase of theta-band (2–6 Hz) but not alpha-band (8–12 Hz) oscillations before target. Detection rates were higher and responses faster when oscillatory power was low and both detection rate and response speed were modulated by phase. Intriguingly, the phase dependency was stronger for miss than for hit trials, suggesting that phase has a inhibiting but not ensuring role for detection. Entrainment of theta range oscillations prominently occurs during the processing of attended complex stimuli, such as vocalizations and speech. Our results demonstrate that this entrainment to attended sensory environments may have negative effects on the detection of individual tokens within the environment, and they support the notion that specific phase ranges of cortical oscillations act as gatekeepers for perception.},
web_url = {http://www.jneurosci.org/content/32/35/12268.full.pdf+html},
state = {published},
DOI = {10.1523/​JNEUROSCI.1877-12.2012},
author = {Ng BS-W{benedict}, Schroeder T{tschroeder}{Research Group Physiology of Sensory Integration} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ FischerZKSSJLS2012,
title = {Detailed functional and structural characterization of a macular lesion in a rhesus macaque},
journal = {Documenta Ophthalmologica},
year = {2012},
month = {8},
volume = {125},
number = {3},
pages = {179-194},
abstract = {Animal models are powerful tools to broaden our understanding in disease mechanisms and to develop future treatment strategies. Here we present detailed
structural and functional findings of a rhesus macaque suffering from a naturally occurring bilateral macular dystrophy (BMD), partial optic atrophy and corresponding
reduction of central V1 signals in visual fMRI experiments when compared to data in a healthy macaque (CTRL) of similar age. Fluorescence and indocyanine green
angiography showed reduced macular vascularization with significantly larger foveal avascular zones (FAZ) in the affected animal (FAZBMD = 8.85 mm2 vs. FAZCTRL =
0.32 mm2). Optical coherence tomography showed bilateral thinning of the macula within the FAZ (total retinal thickness, TRTBMD = 174 ± 9 μm) and partial optic nerve
atrophy when compared to control (TRTCTRL = 303 ± 45 μm). Segmentation analysis revealed that inner retinal layers were primarily affected (inner retinal thickness,
IRTBMD = 33 ± 9 μm vs. IRTCTRL = 143 ± 45 μm), while the outer retina essentially maintained its thickness (ORTBMD = 141 ± 7 μm vs. ORTCTRL = 160 ± 11 μm).
Accordingly, a strong central reduction in the multifocal electroretinography and a specific attenuation of cone-derived signals in Ganzfeld electroretinography was found, whereas rod function remained normal.
We provided detailed characterization of a primate macular disorder. This study aims to stimulate awareness and further investigation in primates with macular disorders
eventually leading to the identification of a primate animal model and facilitating the preclinical development of therapeutic strategies.},
web_url = {http://link.springer.com/content/pdf/10.1007%2Fs10633-012-9340-3},
state = {published},
DOI = {10.1007/s10633-012-9340-3},
author = {Fischer MD, Zobor D, Keliris GA{george}{Department Physiology of Cognitive Processes}, Shao Y{yshao}{Department Physiology of Cognitive Processes}, Seeliger MW, Haverkamp S, J\"agle H, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Smirnakis SM}
}

@Article{ Logothetis2012,
title = {Intracortical recordings and fMRI: An attempt to study operational modules and networks simultaneously},
journal = {NeuroImage},
year = {2012},
month = {8},
volume = {62},
number = {2},
pages = {962–969},
abstract = {The brain can be envisaged as a complex adaptive system. It is characterized by a very high structural complexity and by massive connectivity, both of which change and evolve in response to experience. Information related to sensors and effectors is processed in both a parallel and a hierarchical fashion; the connectivity between different hierarchical levels is bidirectional, and its effectiveness is continuously controlled by specific associational and neuromodulatory centers. When questions are addressed at the level of a distributed, large-scale whole system such as that underlying perception and cognition, it is not clear what should be considered as an elementary operational unit because the behavior of integral, aggregate systems is always emergent and most often remains unpredicted by the behaviors of single cells. To localize and comprehend the neural mechanisms underlying our perceptual or cognitive capacities, concurrent studies of microcircuits, of local and long-range interconnectivity between small assemblies, and of the synergistic activity of larger neuronal populations are called for. In other words, multimodal methodologies that include invasive neuroscientific methods as well as global neuroimaging techniques are required, such as the various functional aspects of magnetic resonance imaging. These facts were the driving force behind the decision to begin animal-MRI in my lab. The wonderful idea of the editors of NeuroImage to publish a Special Issue commemorating 20 years of functional fMRI provides me with the opportunity of sharing not only our first moments of frustration with the readers, but also our successful results.},
web_url = {http://www.sciencedirect.com/science/article/pii/S105381191200050X},
state = {published},
DOI = {10.1016/j.neuroimage.2012.01.033},
author = {Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ BiessmannMLMM2012,
title = {Improved decoding of neural activity from fMRI signals using non-separable spatiotemporal deconvolutions},
journal = {NeuroImage},
year = {2012},
month = {7},
volume = {61},
number = {4},
pages = {1031–1042},
abstract = {The goal of most functional Magnetic Resonance Imaging (fMRI) analyses is to investigate neural activity. Many fMRI analysis methods assume that the temporal dynamics of the hemodynamic response function (HRF) to neural activation is separable from its spatial dynamics. Although there is empirical evidence that the HRF is more complex than suggested by space–time separable canonical HRF models, it is difficult to assess how much information about neural activity is lost when assuming space–time separability. In this study we directly test whether spatiotemporal variability in the HRF that is not captured by separable models contains information about neural signals. We predict intracranially measured neural activity from simultaneously recorded fMRI data using separable and non-separable spatiotemporal deconvolutions of voxel time series around the recording electrode. Our results show that abandoning the spatiotemporal separability assumption consistently improves the decoding accuracy of neural signals from fMRI data. We compare our findings with results from optical imaging and fMRI studies and discuss potential implications for classical fMRI analyses without invasive electrophysiological recordings.},
web_url = {http://www.sciencedirect.com/science/article/pii/S1053811912003965},
state = {published},
DOI = {10.1016/j.neuroimage.2012.04.015},
author = {Biessmann F{fbiessma}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, M\"uller KR{klaus} and Meinecke FC}
}

@Article{ Bartels2012,
title = {Oxytocin and the Social Brain: Beware the Complexity},
journal = {Neuropsychopharmacology},
year = {2012},
month = {7},
volume = {37},
number = {8},
pages = {1795–1796},
abstract = {Love, or in more functional–biological terms, social attachment or bonding, is the evolutionary key to the existence of species like humans: our babies’ survival depends entirely on parental care, which in turn provides the opportunity to transmit a vast amount of knowledge from one generation to the next. It is therefore no surprise that the brain's mechanisms that evolved to ensure parent–child bonding are powerful and under genetic control.},
web_url = {http://www.nature.com/npp/journal/v37/n8/pdf/npp201271a.pdf},
state = {published},
DOI = {10.1038/npp.2012.71},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Article{ ValverdeSalzmannBLS2012,
title = {Color Blobs in Cortical Areas V1 and V2 of the New World Monkey Callithrix jacchus, Revealed by Non-Differential Optical Imaging},
journal = {Journal of Neuroscience},
year = {2012},
month = {6},
volume = {32},
number = {23},
pages = {7881-7894},
abstract = {Color vision is reserved to only few mammals, such as Old World monkeys and humans. Most Old World monkeys are trichromats. Among them, macaques were shown to exhibit functional domains of color-selectivity, in areas V1 and V2 of the visual cortex. Such color domains have not yet been shown in New World monkeys. In marmosets a sex-linked dichotomy results in dichromatic and trichromatic genotypes, rendering most male marmosets color-blind. Here we used trichromatic female marmosets to examine the intrinsic signal response in V1 and V2 to chromatic and achromatic stimuli, using optical imaging. To activate the subsystems individually, we used spatially homogeneous isoluminant color opponent (red/green, blue/yellow) and hue versus achromatic flicker (red/gray, green/gray, blue/gray, yellow/gray), as well as achromatic luminance flicker. In contrast to previous optical imaging studies in marmosets, we find clearly segregated color domains, similar to those seen in macaques. Red/green and red/gray flicker were found to be the appropriate stimulus for revealing color domains in single-condition maps. Blue/gray and blue/yellow flicker stimuli resulted in faint patch-patterns. A recently described multimodal vessel mapping approach allowed for an accurate alignment of the functional and anatomical datasets. Color domains were tightly colocalized with cytochrome oxidase blobs in V1 and with thin stripes in V2. Thus, our findings are in accord with 2-Deoxy-d-glucose studies performed in V1 of macaques and studies on color representation in V2. Our results suggest a similar organization of early cortical color processing in trichromats of both Old World and New World monkeys.},
web_url = {http://www.jneurosci.org/content/32/23/7881.full.pdf+html},
state = {published},
DOI = {10.1523/​JNEUROSCI.4832-11.2012},
author = {Valverde Salzmann MF{valverde}, Bartels A{abartels}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}}
}

@Article{ PanagiotaropoulosDKL2012,
title = {Neuronal Discharges and Gamma Oscillations Explicitly Reflect Visual Consciousness in the Lateral Prefrontal Cortex},
journal = {Neuron},
year = {2012},
month = {6},
volume = {74},
number = {5},
pages = {924–935},
abstract = {Neuronal discharges in the primate temporal lobe, but not in the striate and extrastriate cortex, reliably reflect stimulus awareness. However, it is not clear whether visual consciousness should be uniquely localized in the temporal association cortex. Here we used binocular flash suppression to investigate whether visual awareness is also explicitly reflected in feature-selective neural activity of the macaque lateral prefrontal cortex (LPFC), a cortical area reciprocally connected to the temporal lobe. We show that neuronal discharges in the majority of single units and recording sites in the LPFC follow the phenomenal perception of a preferred stimulus. Furthermore, visual awareness is reliably reflected in the power modulation of high-frequency (>50 Hz) local field potentials in sites where spiking activity is found to be perceptually modulated. Our results suggest that the activity of neuronal populations in at least two association cortical areas represents the content of conscious visual perception.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0896627312003807},
state = {published},
DOI = {10.1016/j.neuron.2012.04.013},
author = {Panagiotaropoulos TI{theofanis}{Department Physiology of Cognitive Processes}, Deco G, Kapoor V{vishal}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ vonPfostlLZGZSLR2012,
title = {Effects of lactate on the early visual cortex of non-human primates, investigated by pharmaco-MRI and neurochemical analysis},
journal = {NeuroImage},
year = {2012},
month = {5},
volume = {61},
number = {1},
pages = {98–105},
abstract = {In contrast to the limited use of functional magnetic resonance imaging (fMRI) in clinical diagnostics, it is currently a mainstay of neuroimaging in clinical and basic brain research. However, its non-invasive use in combination with its high temporal and spatial resolution would make fMRI a perfect diagnostic tool. We are interested in whether a pharmacological challenge imposed on the brain can be reliably traced by the blood oxygen level-dependent (BOLD) signal and possibly further exploited for diagnostics. We have chosen a systemic challenge with lactate and pyruvate to test whether the physiological formation of these monocarboxylic acids contributes to the BOLD signal and can be detected using fMRI. This information is also of interest because lactate levels in the cerebrospinal fluid rise concomitantly with reduced vascular responsiveness of the brain during the progression of Alzheimer disease (AD). We studied the BOLD response after a low-dose lactate challenge and monitored the induced plasma lactate levels in anesthetized non-human primates. We observed reliable lactate-induced BOLD responses, which could be confirmed at population and individual level by their strong correlation with systemic lactate concentrations. Comparable BOLD effects where observed after a slow infusion of pyruvate. We show here that physiological changes in lactate and pyruvate levels are indeed reflected in the BOLD signal, and describe the technical prerequisites to reliably trace a lactate challenge using BOLD-fMRI.},
web_url = {http://www.sciencedirect.com/science/article/pii/S1053811912002698},
state = {published},
DOI = {10.1016/j.neuroimage.2012.02.082},
author = {von Pf\"ostl V{vpfoestl}{Department Physiology of Cognitive Processes}, Li J{juan}{Department Physiology of Cognitive Processes}, Zaldivar D{dzaldivar}{Department Physiology of Cognitive Processes}, Goense J{jozien}{Department Physiology of Cognitive Processes}, Zhang X{xiaozhe}{Department Physiology of Cognitive Processes}, Serr N{nserr}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rauch A{arauch}{Department Physiology of Cognitive Processes}}
}

@Article{ EvrardFL2012_2,
title = {Von economo neurons in the anterior insula of the macaque monkey},
journal = {Neuron},
year = {2012},
month = {5},
volume = {74},
number = {3},
pages = {482–489},
abstract = {The anterior insular cortex (AIC) and its unique spindle-shaped von Economo neuron (VEN) emerged within the last decade as having a potentially major role in self-awareness and social cognition in humans. Invasive examination of the VEN has been precluded so far by the assumption that this neuron occurs among primates exclusively in humans and great apes. Here, we demonstrate the presence of the VEN in the agranular anterior insula of the macaque monkey. The morphology, size, laminar distribution, and proportional distribution of the monkey VEN suggest that it is at least a primal anatomical homolog of the human VEN. This finding sheds new light on the phylogeny of the VEN and AIC. Most importantly, it offers new and much-needed opportunities to investigate the primal connections and physiology of a neuron that could be crucial for human self-awareness, social cognition, and related neuropsychiatric disorders.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0896627312002267},
state = {published},
DOI = {10.1016/j.neuron.2012.03.003},
author = {Evrard HC{evrard}{Department Physiology of Cognitive Processes}, Forro T{tforro}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ MishraJEL2012,
title = {Synthesis and in Vitro Evaluation of a Biotinylated Dextran-Derived Probe for Molecular Imaging},
journal = {ACS Chemical Neuroscience},
year = {2012},
month = {4},
volume = {3},
number = {4},
pages = {268–273},
abstract = {Herein we report the design, synthesis, and in vitro evaluation of a gadolinium-containing biotinylated dextran-derived molecular imaging probe as a prospective neuroanatomical tracer by means of magnetic resonance imaging (MRI). The probe was effectively taken up by cultured differentiated murine neuroblastoma cells and significantly enhanced the contrast in T1- and T2-weighted MR images of labeled cells under physiological conditions. A significant longitudinal relaxation rate enhancement in the presence of avidin was observed allowing the verification of the results in the end of noninvasive longitudinal MRI connectivity studies by post-mortem histology. The in vitro results indicate that the probe has the potential to be used in vivo to identify the organization of global neuronal networks in the brain with MRI.},
web_url = {http://pubs.acs.org/doi/pdf/10.1021/cn200112v},
state = {published},
DOI = {10.1021/cn200112v},
author = {Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Joshi R{raju}{Department High-Field Magnetic Resonance}, Engelmann J{joern}{Department High-Field Magnetic Resonance} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ FischerLBB2011,
title = {Visual Motion Responses in the Posterior Cingulate Sulcus: A Comparison to V5/MT and MST},
journal = {Cerebral Cortex},
year = {2012},
month = {4},
volume = {22},
number = {4},
pages = {865-876},
abstract = {Motion processing regions apart from V5+/MT+ are still relatively poorly understood. Here, we used functional magnetic resonance imaging to perform a detailed functional analysis of the recently described cingulate sulcus visual area (CSv) in the dorsal posterior cingulate cortex. We used distinct types of visual motion stimuli to compare CSv with V5/MT and MST, including a visual pursuit paradigm. Both V5/MT and MST preferred 3D flow over 2D planar motion, responded less yet substantially to random motion, had a strong preference for contralateral versus ipsilateral stimulation, and responded nearly equally to contralateral and to full-field stimuli. In contrast, CSv had a pronounced preference to 2D planar motion over 3D flow, did not respond to random motion, had a weak and nonsignificant lateralization that was significantly smaller than that of MST, and strongly preferred full-field over contralateral stimuli. In addition, CSv had a better capability to integrate eye movements with retinal motion compared with V5/MT and MST. CSv thus differs from V5+/MT+ by its unique preference to full-field, coherent, and planar motion cues. These results place CSv in a good position to process visual cues related to self-induced motion, in particular those associated to eye or lateral head movements.},
web_url = {http://cercor.oxfordjournals.org/content/22/4/865.full.pdf+html},
state = {published},
DOI = {10.1093/cercor/bhr154},
author = {Fischer E{efischer}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, B\"ulthoff HH{hhb}{Department Human Perception, Cognition and Action} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Article{ Scholkopf2012,
title = {A Kernel Two-Sample Test},
journal = {Journal of Machine Learning Research},
year = {2012},
month = {3},
volume = {13},
pages = {723−773},
abstract = {We propose a framework for analyzing and comparing distributions, which we use to construct statistical tests to determine if two samples are drawn from different distributions. Our test statistic is the largest difference in expectations over functions in the unit ball of a reproducing kernel Hilbert space (RKHS), and is called the maximum mean discrepancy (MMD). We present two distribution-free tests based on large deviation bounds for the MMD, and a third test based on the asymptotic distribution of this statistic. The MMD can be computed in quadratic time, although efficient linear time approximations are available. Our statistic is an instance of an integral probability metric, and various classical metrics on distributions are obtained when alternative function classes are used in place of an RKHS. We apply our two-sample tests to a variety of problems, including attribute matching for databases using the Hungarian marriage method, where they perform strongly. Excellent performance is also obtained when comparing distributions over graphs, for which these are the first such tests.},
web_url = {http://jmlr.csail.mit.edu/papers/v13/gretton12a.html},
state = {published},
author = {Gretton A{arthur}{Department Empirical Inference}, Borgwardt K{karsten}, Rasch M{rasch}{Department Physiology of Cognitive Processes}, Sch\"olkopf B{bs}{Department Empirical Inference} and Smola A{smola}}
}

@Article{ FischerBLB2012,
title = {Human Areas V3A and V6 Compensate for Self-Induced Planar Visual Motion},
journal = {Neuron},
year = {2012},
month = {3},
volume = {73},
number = {6},
pages = {1228-1240},
abstract = {Little is known about mechanisms mediating a stable perception of the world during pursuit eye movements. Here, we used fMRI to determine to what extent human motion-responsive areas integrate planar retinal motion with nonretinal eye movement signals in order to discard self-induced planar retinal motion and to respond to objective (“real”) motion. In contrast to other areas, V3A lacked responses to self-induced planar retinal motion but responded strongly to head-centered motion, even when retinally canceled by pursuit. This indicates a near-complete multimodal integration of visual with nonvisual planar motion signals in V3A. V3A could be mapped selectively and robustly in every single subject on this basis. V6 also reported head-centered planar motion, even when 3D flow was added to it, but was suppressed by retinal planar motion. These findings suggest a dominant contribution of human areas V3A and V6 to head-centered motion perception and to perceptual stability during eye movements.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0896627312001407},
state = {published},
DOI = {10.1016/j.neuron.2012.01.022},
author = {Fischer E{efischer}{Department Physiology of Cognitive Processes}, B\"ulthoff HH{hhb}{Department Human Perception, Cognition and Action}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Article{ LivZZLR2011,
title = {Measuring multiple neurochemicals and related metabolites in blood and brain of the rhesus monkey by using dual microdialysis sampling and capillary hydrophilic interaction chromatography-mass spectrometry},
journal = {Analytical and Bioanalytical Chemistry},
year = {2012},
month = {3},
volume = {402},
number = {8},
pages = {2545-2554},
abstract = {In vivo measurement of multiple functionally related neurochemicals and metabolites (NMs) is highly interesting but remains challenging in the field of basic neuroscience and clinical research. We present here an analytical method for determining five functionally and metabolically related polar substances, including acetylcholine (quaternary ammonium), lactate and pyruvate (organic acids), as well as glutamine and glutamate (amino acids). These NMs are acquired from samples of the brain and the blood of non-human primates in parallel by dual microdialysis, and subsequently analyzed by a direct capillary hydrophilic interaction chromatography (HILIC)–mass spectrometry (MS) based method. To obtain high sensitivity in electrospray ionization (ESI)–MS, lactate and pyruvate were detected in negative ionization mode whereas the other NMs were detected in positive ionization mode during each HILIC-MS run. The method was validated for linearity, the limits of detection and quantification, precision, accuracy, stability and matrix effect. The detection limit of acetylcholine, lactate, pyruvate, glutamine, and glutamate was 150 pM, 3 μM, 2 μM, 5 nM, and 50 nM, respectively. This allowed us to quantitatively and simultaneously measure the concentrations of all the substances from the acquired dialysates. The concentration ratios of both lactate/pyruvate and glutamine/glutamate were found to be higher in the brain compared to blood (p < 0.05). The reliable and simultaneous quantification of these five NMs from brain and blood samples allows us to investigate their relative distribution in the brain and blood, and most importantly paves the way for future non-invasive studies of the functional and metabolic relation of these substances to each other.},
web_url = {http://www.springerlink.com/content/m75q3716w21h6u5g/fulltext.pdf},
state = {published},
DOI = {10.1007/s00216-011-5427-z},
author = {Li J{juan}{Department Physiology of Cognitive Processes}, von Pf\"ostl V{vpfoestl}{Department Physiology of Cognitive Processes}, Zaldivar D{dzaldivar}{Department Physiology of Cognitive Processes}, Zhang X{xiaozhe}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rauch A{arauch}{Department Physiology of Cognitive Processes}}
}

@Article{ LiebeHLR2012,
title = {Theta coupling between V4 and prefrontal cortex predicts visual short-term memory performance},
journal = {Nature Neuroscience},
year = {2012},
month = {3},
volume = {15},
number = {3},
pages = {456-462},
abstract = {Short-term memory requires communication between multiple brain regions that collectively mediate the encoding and maintenance of sensory information. It has been suggested that oscillatory synchronization underlies intercortical communication. Yet, whether and how distant cortical areas cooperate during visual memory remains elusive. We examined neural interactions between visual area V4 and the lateral prefrontal cortex using simultaneous local field potential (LFP) recordings and single-unit activity (SUA) in monkeys performing a visual short-term memory task. During the memory period, we observed enhanced between-area phase synchronization in theta frequencies (3–9 Hz) of LFPs together with elevated phase locking of SUA to theta oscillations across regions. In addition, we found that the strength of intercortical locking was predictive of the animals' behavioral performance. This suggests that theta-band synchronization coordinates action potential communication between V4 and prefrontal cortex that may contribute to the maintenance of visual short-term memories.},
web_url = {http://www.nature.com/neuro/journal/v15/n3/full/nn.3038.html},
state = {published},
DOI = {10.1038/nn.3038},
author = {Liebe S{sliebe}{Department Physiology of Cognitive Processes}, Hoerzer GM, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Article{ MamedovEEBL2011,
title = {Dual-functional probes towards in vivo studies of brain connectivity and plasticity},
journal = {Chemical Communications},
year = {2012},
month = {2},
volume = {48},
number = {22},
pages = {2755-2757},
abstract = {A Gd3+ based paramagnetic dextran conjugate has been developed, which enables the tracking of neuroanatomical connectivity in the brain by both MR and optical imaging. Cell studies and subsequent in vivo experiments in rodents demonstrate efficient internalisation and transport properties of the new tracer molecule.},
web_url = {http://pubs.rsc.org/en/Content/ArticleLanding/2012/CC/c1cc15991g},
state = {published},
DOI = {10.1039/C1CC15991G},
author = {Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, Engelmann J{joern}{Department High-Field Magnetic Resonance}, Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ BrasseletPLK2012,
title = {Neurons with stereotyped and rapid responses provide a reference frame for relative temporal coding in primate auditory cortex},
journal = {Journal of Neuroscience},
year = {2012},
month = {2},
volume = {32},
number = {9},
pages = {2998-3008},
abstract = {The precise timing of spikes of cortical neurons relative to stimulus onset carries substantial sensory information. To access this information the sensory systems would need to maintain an internal temporal reference that reflects the precise stimulus timing. Whether and how sensory systems implement such reference frames to decode time-dependent responses, however, remains debated. Studying the encoding of naturalistic sounds in primate (Macaca mulatta) auditory cortex we here investigate potential intrinsic references for decoding temporally precise information. Within the population of recorded neurons, we found one subset responding with stereotyped fast latencies that varied little across trials or stimuli, while the remaining neurons had stimulus-modulated responses with longer and variable latencies. Computational analysis demonstrated that the neurons with stereotyped short latencies constitute an effective temporal reference for relative coding. Using the response onset of a simultaneously recorded stereotyped neuron allowed decoding most of the stimulus information carried by onset latencies and the full spike train of stimulus-modulated neurons. Computational modeling showed that few tens of such stereotyped reference neurons suffice to recover nearly all information that would be available when decoding the same responses relative to the actual stimulus onset. These findings reveal an explicit neural signature of an intrinsic reference for decoding temporal response patterns in the auditory cortex of alert animals. Furthermore, they highlight a role for apparently unselective neurons as an early saliency signal that provides a temporal reference for extracting stimulus information from other neurons.},
web_url = {http://www.jneurosci.org/content/32/9/2998.full.pdf+html},
state = {published},
DOI = {10.1523/​JNEUROSCI.5435-11.2012},
author = {Brasselet R{rbrasselet}{Department Physiology of Cognitive Processes}, Panzeri S{stefano}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ EschenkoMPS2011,
title = {Noradrenergic Neurons of the Locus Coeruleus Are Phase Locked to Cortical Up-Down States during Sleep},
journal = {Cerebral Cortex},
year = {2012},
month = {2},
volume = {22},
number = {2},
pages = {426-435},
abstract = {Nonrapid eye movement (NREM) sleep is characterized by periodic changes in cortical excitability that are reflected in the electroencephalography (EEG) as high-amplitude slow oscillations, indicative of cortical Up/Down states. These slow oscillations are thought to be involved in NREM sleep-dependent memory consolidation. Although the locus coeruleus (LC) noradrenergic system is known to play a role in off-line memory consolidation (that may occur during NREM sleep), cortico–coerulear interactions during NREM sleep have not yet been studied in detail. Here, we investigated the timing of LC spikes as a function of sleep-associated slow oscillations. Cortical EEG was monitored, along with activity of LC neurons recorded extracellularly, in nonanesthetized naturally sleeping rats. LC spike-triggered averaging of EEG, together with phase-locking analysis, revealed preferential firing of LC neurons along the ascending edge of the EEG slow oscillation, correlating with Down-to-Up state transition. LC neurons were locked best when spikes were shifted forward ∼50 ms in time with respect to the EEG slow oscillation. These results suggest that during NREM sleep, firing of LC neurons may contribute to the rising phase of the EEG slow wave by providing a neuromodulatory input that increases cortical excitability, thereby promoting plasticity within these circuits.},
web_url = {http://cercor.oxfordjournals.org/content/22/2/426.full.pdf+html},
state = {published},
DOI = {10.1093/cercor/bhr121},
author = {Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}, Magri C{cmagri}{Department Physiology of Cognitive Processes}, Panzeri S{stefano} and Sara SJ}
}

@Article{ TuriGSVMW2011,
title = {Quantifying additive evoked contributions to the event-related potential},
journal = {NeuroImage},
year = {2012},
month = {2},
volume = {59},
number = {3},
pages = {2607–2624},
abstract = {Event-related potentials (ERPs) are widely used in basic neuroscience and in clinical diagnostic procedures. In contrast, neurophysiological insights from ERPs have been limited, as several different mechanisms led to ERPs. Apart from stereotypically repeated responses (additive evoked responses), these mechanisms are asymmetric amplitude modulations and phase-resetting of ongoing oscillatory activity. Therefore, a method is needed that differentiates between these mechanisms and moreover quantifies the stability of a response. We propose a constrained subspace independent component analysis that exploits the multivariate information present in the all-to-all relationship of recordings over trials. Our method identifies additive evoked activity and quantifies its stability over trials. We evaluate identification performance for biologically plausible simulation data and two neurophysiological test cases: Local field potential (LFP) recordings from a visuo-motor-integration task in the awake behaving macaque and magnetoencephalography (MEG) recordings of steady-state visual evoked fields (SSVEFs). In the LFPs we find additive evoked response contributions in visual areas V2/4 but not in primary motor cortex A4, although visually triggered ERPs were also observed in area A4. MEG-SSVEFs were mainly created by additive evoked response contributions. Our results demonstrate that the identification of additive evoked response contributions is possible both in invasive and in non-invasive electrophysiological recordings.},
web_url = {http://www.sciencedirect.com/science/article/pii/S105381191101010X},
state = {published},
DOI = {10.1016/j.neuroimage.2011.08.078},
author = {Turi G, Gotthardt S, Singer W, Vuong TA, Munk M{munk}{Department Physiology of Cognitive Processes} and Wibral M}
}

@Article{ CavusogluBYU2011,
title = {Retinotopic maps and hemodynamic delays in the human visual cortex measured using arterial spin labeling},
journal = {NeuroImage},
year = {2012},
month = {2},
volume = {59},
number = {4},
pages = {4044–4054},
abstract = {Cortical representations of the visual field are organized retinotopically, such that nearby neurons have receptive fields at nearby locations in the image. Many studies have used blood oxygenation level-dependent (BOLD) fMRI to non-invasively construct retinotopic maps in humans. The accuracy of the maps depends on the spatial extent of the metabolic and hemodynamic changes induced by the neural activity. Several studies using gradient-echo MRI at 1.5 T and 3 T showed that most of the BOLD signal originates from veins, which might lead to a spatial displacement from the actual site of neuronal activation, thus reducing the specificity of the functional localization. In contrast to BOLD signal, cerebral blood flow (CBF) as measured using arterial spin labeling (ASL) is less or not at all affected by remote draining veins, and therefore spatially and temporally more closely linked to the underlying neural activity. In the present study, we determined retinotopic maps in the human brain using CBF as well as using BOLD signal in order to compare their spatial relationship and the temporal delays of each imaging modality for visual areas V1, V2, V3, hV4 and V3AB. We tested the robustness and reproducibility of the maps across different sessions, calculated the overlap as well as signal delay times across visual areas. While area boundaries were relatively well preserved, we found systematic differences of response latencies between CBF and the BOLD signal between areas. In summary, CBF data obtained using ASL allows reliable retinotopic maps to be constructed; this approach is, therefore, suitable for studying visual areas especially in close proximity to large veins where the BOLD signal is spatially inaccurate.},
web_url = {http://www.sciencedirect.com/science/article/pii/S1053811911012201},
state = {published},
DOI = {10.1016/j.neuroimage.2011.10.056},
author = {Cavusoglu M{mustafa}{Department High-Field Magnetic Resonance}, Bartels A{abartels}{Department Physiology of Cognitive Processes}, Yesilyurt B{baris}{Department High-Field Magnetic Resonance} and Uludag K{kuludag}{Department High-Field Magnetic Resonance}}
}

@Article{ KayserR2012,
title = {Suppressive Competition: How Sounds May Cheat Sight},
journal = {Neuron},
year = {2012},
month = {2},
volume = {73},
number = {4},
pages = {627–629},
abstract = {In this issue of Neuron, Iurilli et al. (2012) demonstrate that auditory cortex activation directly engages local GABAergic circuits in V1 to induce sound-driven hyperpolarizations in layer 2/3 and layer 6 pyramidal neurons. Thereby, sounds can directly suppress V1 activity and visual driven behavior.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0896627312001262},
state = {published},
DOI = {10.1016/j.neuron.2012.02.001},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration} and Remedios R{ryan}{Research Group Physiology of Sensory Integration}}
}

@Article{ EschenkoENBML2011,
title = {Tracing of noradrenergic projections using manganese-enhanced MRI},
journal = {NeuroImage},
year = {2012},
month = {2},
volume = {59},
number = {4},
pages = {3252–3265},
abstract = {We examined the applicability of manganese-enhanced MRI (MEMRI) to the in vivo tracing of diffuse neuromodulatory projections by means of simultaneous iontophoretic injections of an extremely low, non-toxic concentration of MnCl2 (10 mM) and fluorescent dextran in the locus coeruleus (LC) in the rat. We validated the use of the iontophoretic injection by reproducing previously reported results from pressure injections of MnCl2 in primary somatosensory cortex. Twenty four hours after injection in LC, Mn2 + labeling was detected in major cortical and subcortical targets of LC projections including predominantly ipsilateral primary motor and somatosensory cortices, hippocampus and amygdala. Although the injections were in most cases centered in the core of LC, the pattern of Mn2 + labeling greatly varied across rats. In addition, despite a certain degree of overlap of the labeling obtained with both MEMRI and classical tracing, MEMRI tracing consistently failed to reliably label not only several minor but also major targets of LC, notably the thalamus. The lack of Mn2 + labeling in thalamus possibly reflected a weaker functional connectivity within coeruleothalamic projections that could not be predicted by anatomical tracing. Inversely, a number of brain regions, particularly contralateral motor cortex, that were not or only sparsely labeled with fluorescent dextran were strongly labeled by Mn2 +. This discrepancy could be partly due to both the activity-dependent and transsynaptic nature of Mn2 + transport. The overall labeling produced using MEMRI with iontophoretic injections in LC indicates that the Mn2 + imaging of highly diffuse projections is in principle feasible. However, the labeling pattern of each individual case needs to be carefully interpreted particularly before submitting data for group analysis or in the case of longitudinal examination of discrete changes in functional connectivity under various physiological or behavioral conditions.},
web_url = {http://www.sciencedirect.com/science/article/pii/S1053811911013127},
state = {published},
DOI = {10.1016/j.neuroimage.2011.11.031},
author = {Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}, Evrard HC{evrard}{Department Physiology of Cognitive Processes}, Neves RM{ricardo}{Department Physiology of Cognitive Processes}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ StoewerGKBLDS2012,
title = {An Analysis Approach for High-Field fMRI Data from Awake Non-Human Primates},
journal = {PLoS One},
year = {2012},
month = {1},
volume = {7},
number = {1},
pages = {1-13},
abstract = {fMRI experiments with awake non-human primates (NHP) have seen a surge of applications in recent years. However, the standard fMRI analysis tools designed for human experiments are not optimal for analysis of NHP fMRI data collected at high fields. There are several reasons for this, including the trial-based nature of NHP experiments, with inter-trial periods being of no interest, and segmentation artefacts and distortions that may result from field changes due to movement. We demonstrate an approach that allows us to address some of these issues consisting of the following steps: 1) Trial-based experimental design. 2) Careful control of subject movement. 3) Computer-assisted selection of trials devoid of artefacts and animal motion. 4) Nonrigid between-trial and rigid within-trial realignment of concatenated data from temporally separated trials and sessions. 5) Linear interpolation of inter-trial intervals and high-pass filtering of temporally continuous data 6) Removal of interpolated data and reconcatenation of datasets before statistical analysis with SPM. We have implemented a software toolbox, fMRI Sandbox (http://code.google.com/p/fmri-sandbox/), for semi-automated application of these processing steps that interfaces with SPM software. Here, we demonstrate that our methodology provides significant improvements for the analysis of awake monkey fMRI data acquired at high-field. The method may also be useful for clinical applications with subjects that are unwilling or unable to remain motionless for the whole duration of a functional scan.},
web_url = {http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0029697},
state = {published},
DOI = {10.1371/journal.pone.0029697},
EPUB = {e29697},
author = {Stoewer S{stoewer}{Department Physiology of Cognitive Processes}, Goense J{jozien}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Bartels A{abartels}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Duncan J and Sigala N{natasha}{Department Physiology of Cognitive Processes}}
}

@Article{ BorchersHLK2012,
title = {Direct electrical stimulation of human cortex: the gold standard for mapping brain functions?},
journal = {Nature Reviews Neuroscience},
year = {2012},
month = {1},
volume = {13},
number = {1},
pages = {63-70},
abstract = {Despite its clinical relevance, direct electrical stimulation (DES) of the human brain is surprisingly poorly understood. Although we understand several aspects of electrical stimulation at the cellular level, surface DES evokes a complex summation effect in a large volume of brain tissue, and the effect is difficult to predict as it depends on many local and remote physiological and morphological factors. The complex stimulation effects are reflected in the heterogeneity of behavioural effects that are induced by DES, which range from evocation to inhibition of responses — sometimes even when DES is applied at the same cortical site. Thus, it is a misconception that DES — in contrast to other neuroscience techniques — allows us to draw unequivocal conclusions about the role of stimulated brain areas.},
web_url = {http://www.nature.com/nrn/journal/v13/n1/pdf/nrn3140.pdf},
state = {published},
DOI = {10.1038/nrn3140},
author = {Borchers S{svenja}, Himmelbach M, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Karnath HO}
}

@Article{ GoenseWL2012,
title = {Neural and BOLD responses across the brain},
journal = {Wiley Interdisciplinary Reviews: Cognitive Science},
year = {2012},
month = {1},
volume = {3},
number = {1},
pages = {75–86},
abstract = {Functional Magnetic Resonance Imaging (fMRI) has quickly grown into one of the most important tools for studying brain function, especially in humans. Despite its prevalence, we still do not have a clear picture of what exactly the blood oxygenation level dependent (BOLD) signal represents or how it compares to the signals obtained with other methods (e.g., electrophysiology). We particularly refer to single neuron recordings and electroencephalography when we mention ‘electrophysiological methods’, given that these methods have been used for more than 50 years, and have formed the basis of much of our current understanding of brain function. Brain function involves the coordinated activity of many different areas and many different cell types that can participate in an enormous variety of processes (neural firing, inhibitory and excitatory synaptic activity, neuromodulation, oscillatory activity, etc.). Of these cells and processes, only a subset is sampled with electrophysiological techniques, and their contribution to the recorded signals is not exactly known. Functional imaging signals are driven by the metabolic needs of the active cells, and are most likely also biased toward certain cell types and certain neural processes, although we know even less about which processes actually drive the hemodynamic response. This article discusses the current status on the interpretation of the BOLD signal and how it relates to neural activity measured with electrophysiological techniques.},
web_url = {http://onlinelibrary.wiley.com/doi/10.1002/wcs.153/pdf},
state = {published},
DOI = {10.1002/wcs.153},
author = {Goense J{jozien}{Department Physiology of Cognitive Processes}, Whittingstall K{kevin}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ MishraGEP2011,
title = {Responsive imaging probes for metabotropic glutamate receptors},
journal = {Chemical Science},
year = {2012},
month = {1},
volume = {3},
number = {1},
pages = {131-135},
abstract = {The design, synthesis and evaluation of eight contrast agents for metabotropic glutamate receptors is reported. Each of the contrast agents contains a selective mGluR5 binding moiety linked to a ‘DOTA’-derived gadolinium complex. The potential of these systems was evaluated in vitro for application as responsive MR imaging probes. The targeting moieties mGluR5 antagonists based on aromatic alkyne and dipyridyl/heterobiaryl amide derivatives integrated in a modular fashion, involving linkage to the macrocyclic DOTA ligand to allow specific binding to the mGluR5 receptors. Signal intensity enhancements of up to 27% were observed by MRI in primary astrocyte suspensions and the reversibility of probe binding to the receptor sites, induced by added glutamate, was demonstrated using optical emission and the antagonistic activity of complexes was defined by calcium binding assays.},
web_url = {http://pubs.rsc.org/en/content/articlepdf/2011/sc/c1sc00418b},
state = {published},
DOI = {10.1039/C1SC00418B},
author = {Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Gottschalk S{sgott}{Department High-Field Magnetic Resonance}, Engelmann J{joern}{Department High-Field Magnetic Resonance} and Parker D}
}

@Article{ MagriSMPL2011,
title = {The Amplitude and Timing of the BOLD Signal Reflects the Relationship between Local Field Potential Power at Different Frequencies},
journal = {Journal of Neuroscience},
year = {2012},
month = {1},
volume = {32},
number = {4},
pages = {1395-1407},
abstract = {There is growing evidence that several components of the mass neural activity contributing to the local field potential (LFP) can be partly separated by decomposing the LFP into nonoverlapping frequency bands. Although the blood oxygen level-dependent (BOLD) signal has been found to correlate preferentially with specific frequency bands of the LFP, it is still unclear whether the BOLD signal relates to the activity expressed by each LFP band independently of the others or if, instead, it also reflects specific relationships among different bands. We investigated these issues by recording, simultaneously and with high spatiotemporal resolution, BOLD signal and LFP during spontaneous activity in early visual cortices of anesthetized monkeys (Macaca mulatta). We used information theory to characterize the statistical dependency between BOLD and LFP. We found that the alpha (8–12 Hz), beta (18–30 Hz), and gamma (40–100 Hz) LFP bands were informative about the BOLD signal. In agreement with previous studies, gamma was the most informative band. Both increases and decreases in BOLD signal reliably followed increases and decreases in gamma power. However, both alpha and beta power signals carried information about BOLD that was largely complementary to that carried by gamma power. In particular, the relationship between alpha and gamma power was reflected in the amplitude of the BOLD signal, while the relationship between beta and gamma bands was reflected in the latency of BOLD with respect to significant changes in gamma power. These results lay the basis for identifying contributions of different neural pathways to cortical processing using fMRI.},
web_url = {http://www.jneurosci.org/content/32/4/1395.full.pdf+html},
state = {published},
DOI = {10.1523/​JNEUROSCI.3985-11.2012},
author = {Magri C{cmagri}{Department Physiology of Cognitive Processes}, Schridde U{schridde}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Panzeri S{stefano} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Inproceedings{ BalduzziB2012,
title = {Towards a learning-theoretic analysis of spike-timing dependent plasticity},
year = {2012},
month = {12},
pages = {2465-2473},
abstract = {This paper suggests a learning-theoretic perspective on how synaptic plasticitybenefits global brain functioning. We introduce a model, the selectron, that (i)arises as the fast time constant limit of leaky integrate-and-fire neurons equippedwithspikingtimingdependentplasticity(STDP)and(ii)isamenabletotheoreticalanalysis. We show that the selectron encodes reward estimates into spikes and thatan error bound on spikes is controlled by a spiking margin and the sum of synapticweights. Moreover, the efficacy of spikes (their usefulness to other reward maxi-mizing selectrons) also depends on total synaptic strength. Finally, based on ouranalysis, we propose a regularized version of STDP, and show the regularizationimproves the robustness of neuronal learning when faced with multiple stimuli.},
file_url = {fileadmin/user_upload/files/publications/2012/NIPS-2012-Balduzzi.pdf},
web_url = {http://nips.cc/Conferences/2012/},
editor = {Bartlett, P. , F.C.N. Pereira, L. Bottou, C.J.C. Burges, K.Q. Weinberger},
booktitle = {Advances in Neural Information Processing Systems 25},
event_name = {Twenty-Sixth Annual Conference on Neural Information Processing Systems (NIPS 2012)},
event_place = {Lake Tahoe, Nevada, USA},
state = {published},
author = {Balduzzi D{balduzzi}{Department Empirical Inference} and Besserve M{besserve}{Department Empirical Inference}{Department Physiology of Cognitive Processes}}
}

@Inbook{ BartelsGL2011,
title = {Functional Magnetic Resonance Imaging},
year = {2012},
month = {9},
pages = {410-469},
web_url = {http://audition.ens.fr/brette/HandbookMeasurement/index.htm},
editor = {Brette, R. , A. Destexhe},
publisher = {Cambridge University Press},
address = {Cambridge, UK},
booktitle = {Handbook for Neural Activity Measurement},
state = {published},
ISBN = {978-0-521-51622-8},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}, Goense J{jozien}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Inbook{ MishraDMSEBCL2011,
title = {Biocytin-based contrast agents for molecular imaging: an approach to developing new in vivo neuroanatomical tracers for MRI},
year = {2012},
month = {2},
volume = {1},
pages = {181-204},
abstract = {One of the most striking characteristic of the brain is its profuse neuronal connectivity. Not surprisingly, the function of the nervous system critically depends on the spatiotemporal pattern of intercommunication between different regions of the brain. Both macro- and microscopic aspects of the wiring diagrams of brain circuits are relevant and need to be understood in order to cope with the complexity of the brain function. In this way, for
instance, the long-range connections that carry the functional specification of cortical territories need to be studied together with the detailed microcircuits inside a cortical column. Moreover, the temporal dimension of these wiring diagrams must be investigated since neuronal networks are dynamic structures exhibiting context-dependent changes in synaptic weights (Canals et al., 2009) and numbers (Chklovskii et al., 2004). Investigations
over the last decades strongly suggest that stimulus or task related neural activity is distributed over large parts of the brain, covering different cortical and sub-cortical areas. For a detailed understanding of brain function, it is of prime importance to understand the
organization of the neuronal connections. To chart the anatomical connections between the various components of brain networks, the neuronal tract tracing technique has been proved to be very useful. Thus, experimental tools that allow the exploration of brain circuits at diverse organizational levels are mandatory for the understanding of brain intercommunication and information processing.},
web_url = {http://www.intechopen.com/articles/show/title/biocytin-based-contrast-agents-for-molecular-imaging-an-approach-to-developing-new-in-vivo-neuroanat},
editor = {Bright, P.},
publisher = {InTech},
address = {Rijeka, Croatia},
booktitle = {Neuroimaging - Methods},
state = {published},
ISBN = {978-953-51-0097-3},
DOI = {10.5772/23806},
author = {Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Mishra R{ritu}{Department High-Field Magnetic Resonance}, Canals S{canals}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Engelmann J{joern}{Department High-Field Magnetic Resonance}, Sch\"uz A{schuez}{Department Physiology of Cognitive Processes} and Dhingra K{kirti}{Department Physiology of Cognitive Processes}}
}

@Inbook{ PanzeriI2012,
title = {Information-Theoretic Approaches to Pattern Analysis},
year = {2012},
month = {1},
pages = {565-598},
web_url = {http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=12661},
editor = {Kriegskorte, N. , G. Kreiman},
publisher = {MIT Press},
address = {Camridge, MA, USA},
booktitle = {Visual population codes: toward a common multivariate framework for cell recording and functional imaging},
state = {published},
ISBN = {978-0-262-01624-7},
author = {Panzeri S{stefano} and Ince RAA}
}

@Inbook{ 7051,
title = {Local Field Potentials, BOLD, and Spiking Activity: Relationsships and Physiological Mechanisms},
year = {2012},
month = {1},
pages = {599-624},
web_url = {http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=12661},
editor = {Kriegeskorte, N. , G. Kreiman},
publisher = {MIT Press},
address = {Cambridge, MA, USA},
booktitle = {Visual population codes: toward a common multivariate framework for cell recording and functional imaging},
state = {published},
ISBN = {978-0-26201-624-7},
author = {Berens P{berens}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Tolias AS{atolias}{Department Physiology of Cognitive Processes}}
}

@Inbook{ 6030,
title = {Multisensory Influences on Auditory Processing: Perspectives from fMRI and Electrophysiology},
year = {2012},
month = {1},
pages = {99-114},
abstract = {In this review, we discuss some of the results of early multisensory influences on auditory processing, and provide evidence that sensory integration occurs distributed and across several processing stages. In particular, we discuss some of the methodological aspects relevant for studies seeking to localize and characterize multisensory influences, and emphasize some of the recent results pertaining to speech and voice integration.},
web_url = {http://www.crcnetbase.com/doi/abs/10.1201/b11092-9},
editor = {Murray, M. M. , M. T. Wallace},
publisher = {CRC Press},
address = {Boca Raton, FL, USA},
series = {Frontiers in Neuroscience},
booktitle = {The neural bases of multisensory processes},
state = {published},
ISBN = {978-1-439-81217-4},
DOI = {10.1201/b11092-9},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Petkov C{chrisp}, Remedios R{ryan}{Research Group Physiology of Sensory Integration} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ AzevedoALK2012,
title = {Effects of visual attention on neural processing in Rhesus' V1 by simultaneous electrophysiology and BOLD-fMRI},
year = {2012},
month = {11},
volume = {13},
pages = {36},
abstract = {Attention is a cognitive function thought to enhance our ability to select, process, and perceive only a behaviorally relevant fraction of the immense sensory input impinging on our receptors (Knudsen, 2007). Early electrophysiological studies in primates demonstrate that attention can modulate substantially the firing rate of single cells in extrastriate visual areas but has no
or little impact in the primary visual cortex (Moran & Desimone, 1985). In contrast, attention has been linked to strong bloodoxygen-level-dependent (BOLD) signal modulations in human subjects (Gandhi et al., 1999). Our goal is to understand how selective visual spatial attention
modulates the neuronal activity in primary visual cortex (V1) and how these effects are reflected in the different signals (single unit activity, local field potentials, and BOLD). To this end, we have trained two rhesus macaques to perform an orientation-change detection task in high field fMRI scanners (4.7T, 7T) while we can simultaneously acquire high-resolution fMRI maps and electrophysiological signals. Preliminary results suggest that attention modulates the BOLD and electrophysiological signals in distinct ways.We are currently trying to address the layer specificity of the effects by using MRI compatible multicontact probes and implanted RF coils that provide ultra-high resolution maps of the fMRI activations.},
web_url = {http://www.neuroschool-tuebingen-nena.de/},
event_name = {13th Conference of the Junior Neuroscientists of Tübingen (NeNA 2012)},
event_place = {Schramberg, Germany},
state = {published},
author = {Azevedo FAC{fazevedo}{Department Physiology of Cognitive Processes}, Azevedo LAC{lazevedo}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Keliris G{george}{Department Physiology of Cognitive Processes}}
}

@Poster{ ViswanathZvRL2012,
title = {The role of adenosine in the neurovascular coupling of the BOLD signal in early visual cortex of non-human primates},
year = {2012},
month = {11},
volume = {13},
pages = {48},
abstract = {In this study, CPX, an antagonist of adenosine was used to determine the role of adenosine in uncoupling the vascular and neuronal response observed by the BOLD signal after a strong visual stimulation in primary visual cortex (V1). We systemically and locally applied CPX and pharmacologically manipulated the sensory response in the early visual cortex of anaesthetized macaques. Pharmacological magnetic resonance imaging (phMRI) in combination with electrophysiology was used to determine the impact of CPX on V1. Results were obtained from recordings of the BOLD and electrophysiological activity during the injections.
Systemic application of CPX resulted in a disruption of the visual modulation in the BOLD signal. Local applications of CPX resulted in a decrease in the power of low LFP and an
increase in the power of MUA. In addition it resulted in a decrease in the CV and FF. No significant changes were observed in the BOLD signal after systemic application of phosphate buffered saline, which was used as a control. The results show that we indeed observe dissociation between the vascular and the neuronal activity during adenosinergic modulation.
Apparently adenosine reduces functional hyperaemia, which is reflected by the reduction in BOLD signal, while underlying neuronal activity is increased, indicated by an increase in MUA. Further studies have to be conducted using simultaneous sampling of neurochemicals and phMRI to fully elucidate the functional role of adenosine for the vascular and neuronal interplay in V1.},
web_url = {http://www.neuroschool-tuebingen-nena.de/},
event_name = {13th Conference of the Junior Neuroscientists of Tübingen (NeNA 2012)},
event_place = {Schramberg, Germany},
state = {published},
author = {Viswanath S{sviswanath}{Department Physiology of Cognitive Processes}, Zaldivar D{dzaldivar}{Department Physiology of Cognitive Processes}, von Pf\"ostl V{vpfoestl}{Department Physiology of Cognitive Processes}, Rauch A{arauch}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ EschenkoBOL2012,
title = {BOLD responses evoked by electrical stimulation of Locus Coeruleus in rats under anesthesia},
year = {2012},
month = {10},
volume = {42},
pages = {674.15},
abstract = {We performed a whole-brain fMRI imaging in the rat under urethane anesthesia and studied BOLD responses induced by electrical stimulation of the brain stem noradrenergic nucleus Locus Coeruleus (LC). The rat was implanted with a MRI-compatible custom-made iridium electrode into LC under electrophysiological guidance. A 7T (300 MHz) magnet with a 30-cm horizontal bore (Bruker BioSpec 70/30, Ettlingen, Germany) equipped with a 20cm inner diameter gradient (Bruker BGA-20S Ettlingen, Germany) was used for MRI scanning. The experimental paradigm consisted of 6s baseline sampling, followed by 4s of unilateral LC stimulation and 10s of post-stimulus sampling. Biphasic square pulses (0.05-0.4mA) were delivered to LC at 20-100Hz either continuously for 4s or grouped in 100-500ms trains. These stimulation parameters were efficient in eliciting LC burst firing bilaterally. We also collected BOLD responses induced by peripheral sensory stimulation in the same animal and using the same experimental design (6/4/10s). For visual stimulation we used a luminance flicker presented to both eyes at 16Hz and delivered via fiber optic cables. A mild electrical stimulation (1-5mA) of a forepaw was used as somatosensory stimulation. The fMRI images were collected with spatial resolution of 0.4x0.4x1.0mm and temporal resolution of 1s. BOLD maps were generated by using GLM with standard (HRF-convolved boxcar functions) or neural regressors. We observed a remarkable dichotomy between BOLD responses of cortical and subcortical structures. Specifically, LC stimulation produced positive BOLD responses in the majority of structures belonging to metencephalon, mesencephalon and diencephalon, while negative BOLD responses in the entire neocortex. The robust neuronal activation in thalamic projections of LC was further confirmed by electrophysiological recordings. The cortical inhibition as a result of LC stimulation and associated NE release in cortical targets of LC has been reported in earlier studies. The peripheral sensory stimulation evoked both sensory-specific and non-specific activation/deactivation pattern. Strikingly, the regions of non-specific BOLD responses were common for both sensory modalities and largely overlapped with brain regions that showed responses to LC stimulation. We hypothesize that sensory stimulation activates modality-specific sensory pathways along with LC-NE system; and the LC co-activation produces the observed non-specific BOLD responses.},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Oeltermann A{axel} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ MombielaMAMALUGLCLI2012,
title = {Brainstem afferents to the hippocampal formation: Comparative immunohistochemical study in the Macaca fascicularis monkey},
year = {2012},
month = {10},
volume = {42},
number = {916.24},
abstract = {The synaptic plasticity of the Hippocampal Formation (HF, which includes the dentate gyrus -DG-, CA3, CA2, CA1, subiculum, pre-parasubiculum and the entorhinal cortex -EC) is strongly influenced by neurotransmiters (presumably Dopaminergic -DA, Ventral Tegmental Area-VTA; Noradrenergic -NA, Locus Coeruleus-LC and Serotoninergic -5-HT, Raphe Nuclei- RN, respectively), (Otmakhova and Lisman, 1996; Katsuki et al., 1997), although the anatomical basis of the chemical modulation of memory in the HF is far from being understood.
The neuroanatomical connections between the brainstem and in the HF in the nonhuman primate are still unclear. Previous tracer studies showed retrogradely labeled neurons in the brainstem areas including the VTA, LC and RN, after deposits in the hippocampus (Amaral and Cowan, 1980), as well as in the EC (Insausti et al., 1987). In order to characterize the neurochemical nature of those projections, as well as their topographic and laminar differences, we studied comparatively the distribution on those substances in the HF using immunohistochemical techniques.
Immunohistochemistry for each DA (Tyrosine Hydroxylase, TH), NA (Dopamine Beta Hydroxylase -DBH-, and 5-HT) as well as double-immunohistochemical techniques using Alexa 488 (5-HT detection) and Alexa 568 (TH or DBH labeling) disclosed that:
• The polymorphic layer of the DG had fibers with the three neurotransmitters, whereas the molecular layer showed only TH and 5-HT immunolabeling, without double-stained processes.
• The pyramidal layer of CA3 showed denser 5-HT fiber labeling than TH; CA1 showed only scattered TH and 5-HT fibers, without double labeling profiles.
• The subiculum and presubiculum showed fibers immunoreactive for TH, SER and BHD in the molecular layer. No double-labeled TH-5HT or DBH-5HT fibers were seen.
• The superficial layers of the rostral EC (I and II) displayed TH- or 5-HT-labelled processes, while the most lateral subdivisions of EC (ELR/ELc) had TH- or DBH-positive fibers; they did not show co-localization.
The preferential location of these positive fibers in ELR/ELc is significant, as this portion of the EC receives abundant unimodal and polymodal sensory input and innervates the body and tail of the hippocampus, and therefore it might be an important step for the monoaminergic modulation memory consolidation. Our preliminary anatomical results suggest that the HF function may be modulated independently by monoaminergic neurotransmitters.},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Mombiela DH, Munoz M, Arroyo-Jimenez M, Mohedano-Moriano A, Artacho-Perula E, Legidos-Garcia E, Ubero M{mubero}{Department Physiology of Cognitive Processes}, Gonzalez-Fuentes J, Lagartos-Donate M, Cebada-Sanchez S, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Insausti R}
}

@Poster{ BesserveBML2012,
title = {Centrality of the Mammalian Functional Brain Network},
year = {2012},
month = {10},
volume = {42},
number = {507.20},
abstract = {Brain networks are characterized by strong recurrence, and widespread connectivity. As a consequence it is inherently difficult to tell apart local processing and interactions between structures. This is a major obstacle to the identification of a modular organization of the brain. However, complex network analysis enables to attack the problem from a different angle. Specifically, such analysis may consider directly the whole brain as a network and then characterize its topology.
In this work, we use this framework to identify the polysynaptic topology of functional brain networks with a high spatial resolution. We first estimated network connectivity from fMRI signals by computing statistical dependency measures between pairs of voxels. Then, assuming that a restricted set of core regions relay information to the whole network, we developed a statistical test to characterize the structure of this high dimensional network using the concept of eigenvector centrality [1].
We applied these techniques to fMRI recordings in 6 humans during resting state and 4 monkeys during anesthesia. Eigenvector centrality measures based on correlation enabled us to identify a robust set of central areas that was similar in both species, involving cortical (precuneus, medial prefrontal cortex) and subcortical structures (hippocampus). Further graph theoretic analysis based on random walks allowed clustering these regions into robust groups with dedicated subnetworks of influence and to identify their hierarchical organization (clusters of central regions in human are shown in the figure below).
In sum, centrality revealed a synthesis of the complex topology of functional networks in a consistent restricted set of core regions in monkey and human brains. Further work will investigate the temporal dynamics of these regions, and their influence on the activity of the whole network will be validated by experimental manipulation.},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Besserve M{besserve}{Department Empirical Inference}{Department Physiology of Cognitive Processes}, Bartels A{abartels}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ SchindlerHB2012_2,
title = {Coding of melodic Gestalt in human auditory cortex},
year = {2012},
month = {10},
volume = {42},
number = {462.09},
abstract = {A melody consists of a temporal sequence of pitches. Its ‘Gestalt’ is invariant to absolute pitch but depends on the relation between pitches [[unable to display character: –]] the relative pitch profile. Consequently, a melody can be recognised regardless of the instrument used to play it and it even retains its identity after transposition to a different key, which involves a global change of all pitches in the melodic sequence. In contrast, a change in a melody’s temporal pitch order is usually accompanied with a change in its relative pitch profile and therefore also affects its melodic ‘Gestalt’.
Pitch processing is assumed to occur in the auditory cortex. It is however still unknown whether early auditory regions are capable of integrating pitches over time and whether the resulting representations are invariant with respect to the key of their presentation. Here, we exposed participants to different melodies composed of the same four harmonic pitches during fMRI recordings. Additionally, we presented the same melodies transposed to different keys or played on different instruments.
We found that melodies were invariantly represented by their BOLD activation patterns in primary and secondary auditory cortices across instruments, and also across keys. Our findings extend common hierarchical models of auditory processing by showing that melodies are encoded independent of absolute pitch and based on their relative pitch profile as early as primary auditory cortex.},
web_url = {http://am2012.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Schindler A{aschindler}{Department Physiology of Cognitive Processes}, Herdener M{herdener}{Department High-Field Magnetic Resonance} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ ValverdeSalzmannBLS2012_2,
title = {Color blobs in visual areas V1 and V2 of the common marmoset},
year = {2012},
month = {10},
volume = {52},
number = {261.11},
abstract = {Color vision is reserved to only few mammals, such as Old World monkeys and humans. Most Old World monkeys are trichromats. Among them, macaques were shown to exhibit functional domains of color-selectivity, in areas V1 and V2 of the visual cortex. Such color domains have not yet been shown in New World monkeys. In marmosets a sex-linked dichotomy results in dichromatic and trichromatic genotypes, rendering most male marmosets color-blind. Here we used trichromatic female marmosets to examine the intrinsic signal response in V1 and V2 to chromatic and achromatic stimuli, using optical imaging. In order to activate the visual subsystems individually, we used spatially homogeneous isoluminant color opponent (red/green, blue/yellow) and hue versus achromatic flicker (red/gray, green/gray, blue/gray, yellow/gray), as well as achromatic luminance flicker. In contrast to previous optical imaging studies in marmosets, we find clearly segregated color domains, similar to those seen in macaques. Red/green and red/gray flicker were found to be the appropriate stimulus for revealing color domains in single condition maps (see figure). Blue/gray and blue/yellow flicker stimuli resulted in faint patch-patterns. A recently described multimodal vessel mapping approach allowed for an accurate alignment of the functional and anatomical datasets. Color domains were tightly colocalized with cytochrome oxidase blobs in V1 and with thin stripes in V2. Thus, our findings are in accord with 2-Deoxy-D-glucose studies performed in V1 of macaques and studies on color representation in V2. Our results suggest a similar organization of early cortical color processing in trichromats of both, Old World and New World monkeys.},
file_url = {fileadmin/user_upload/files/publications/2012/Neuroscience-2012-Valverde.pdf},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Valverde Salzmann MF{valverde}{Department High-Field Magnetic Resonance}, Bartels A{abartels}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}}
}

@Poster{ ZaretskayaB2012,
title = {Conscious perception of global motion is related to higher-level motion regions},
year = {2012},
month = {10},
volume = {42},
number = {672.18},
abstract = {The processing of motion in the primate brain is distributed across multiple regions of the cerebral cortex. The two well-studied visual areas MT and MST have been linked to conscious perception and decision-making related to simple flow stimuli as well as to integration of component plaid motion into a coherently moving pattern. However, it is unclear whether processing and perception of other types of global motion, which require large-scale integration of the local signals, is related to activity of the same areas.
In the current study we used fMRI to investigate neural responses to a bi-stable visual motion stimulus. The stimulus consisted of four pairs of dots, each pair coherently moving on a circular path. Perception alternated spontaneously between two states: local dot motion in each of the four quadrants of the visual field or global planar motion of two illusory squares spanning all four visual quadrants [1]. Importantly, these alternations were purely perceptual and involved no stimulus manipulation. We localized visual areas that are known to respond to visual movement (V3a, V6, V7, MT, MST, IPS1-4, and the recently described cingulate sulcus visual area (CSv) [2,3]) individually in each subject. We then investigated responses of these areas to global and local perceptual states of our subjects, while they viewed the bistable stimulus and reported their perception.
We found that activity of two of the areas, CSv and IPS4, specifically correlated with global, but not the local perceptual states, while V6 showed a trend in the opposite direction. Interestingly, neither V5/MT, nor MST, nor any other motion-responsive region differentiated between global and local perceptual states.
Our results suggest that CSv and IPS4 may be involved in the computation of global motion by large-scale integration of similar motion directions, or by spatial binding between distant loci in the visual field, respectively. Importantly, these results imply a certain 'blindness' of V5/MT and of MST to vivid changes in the conscious perception of large-scale motion stimuli. The perception of global, large-scale motion may therefore be mediated by higher-level motion-processing regions with larger receptive fields, such as by areas CSv and IPS4.},
web_url = {http://am2012.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Zaretskaya N{nataliya}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ KwonWFB2012,
title = {Effects of visual attention on BOLD signal variance},
year = {2012},
month = {10},
volume = {42},
number = {673.14},
abstract = {The responses of sensory neurons are noisy, and laboratory studies typically deal with this variability by averaging responses to many stimulus presentations. Recently, it has been observed that the noise signals carry important information about the brain activity, especially by observing the trial-to-trial noise correlation of spiking activity across populations of neurons (Ecker et al. 2010). The trial-to-trial fluctuations in the responses of pairs of neuron are affected by attention, and this has influence on behavior (Cohen et al. 2009, Mitchell et al. 2009). In particular, it was found that attention decreased the noise correlation of neural responses in V4, indicating a more efficient encoding or an increase of information content. Yet the results of these electrophysiology studies left it unclear whether such effects would also occur elsewhere in the cortex, and whether similar effects can be observed in the BOLD signal.
In the present study we asked human participants to perform a difficult, attention-demanding task on a complex visual motion display during a prolonged period of time, alternated by equally long periods of visual stimulation without any task. Brain activity was recorded using fMRI. We then analyzed changes in the mean BOLD signal during both conditions, as well as the signal variance within the time-series of each condition.
During attention, the BOLD signal variance decreased in several regions, including V5/MT, the temporal parietal junction, and in additional medial-frontal regions. Mean BOLD signal increased in early visual cortex, V5/MT, and in the parieto-frontal attention network. The results demonstrate firstly that the variance of BOLD activity can be altered by visual attention. Secondly they show that there is only a partial overlap between regions whose BOLD signal increases and those whose BOLD signal variance changes. This suggests that changes in variance and in net amplitude may reflect distinct brain processes related to attention.},
web_url = {http://am2012.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Kwon S{soyoung}{Department Physiology of Cognitive Processes}, Watanabe M{watanabe}{Department Physiology of Cognitive Processes}, Fischer E{efischer}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ KuGLB2012,
title = {Facial expression and identity encoding in macaques revealed by fMRI adaptation},
year = {2012},
month = {10},
volume = {42},
number = {263.22},
abstract = {fMRI has revealed a face processing network in the macaque brain that encompasses regions in the superior temporal sulcus (STS), the lateral and ventral temporal cortex, the medial temporal lobe and in the prefrontal cortex (Tsao and Livingstone 2008; Ku, Tolias et al. 2011). However, the functionality of each individual face-responsive patch is largely unknown. In humans fMRI evidence suggests that the middle STS is important for facial expression encoding, while the ventral temporal cortex is primarily involved in identity encoding (Haxby, Hoffman et al. 2002). This is consistent with single unit studies showing facial expression selective cells in the STS and identity encoding neurons in LTG in monkeys. However, there is no equivalent evidence indicating such a functional segregation in terms of BOLD responses to face stimuli. In order to examine whether there is a similar response pattern in monkeys and to further identify more candidate brain regions which might be also important in encoding these two aspects of faces, we scanned two awake and five anesthetized monkeys at 7Tesla. Using an adaptation paradigm we found that STS was sensitive to changing facial expressions independent of changing of identities in all awake and anesthetized monkeys. In brain regions not covered in the awake monkeys, the same contrast revealed that the medial orbital frontal cortex (area 47/12 ) of four anesthetized monkeys was also sensitive to changing facial expressions. In addition, we found that the anterior hippocampus of the two awake and three anesthetized monkeys was sensitive to changing identities. The results suggest differential selectivities for the encoding of facial expressions and of identities across a network of regions in the monkey.},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Ku S-P{shihpi}{Department Physiology of Cognitive Processes}, Goense JBG{jozien}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ UberoMartinezMMAMAHLGLCALI2012,
title = {Frontal cortex afferents to the ventral tegmental area in the Macaca fascicularis monkey},
year = {2012},
month = {10},
volume = {42},
number = {701.02},
abstract = {The prefrontal cortico-midbrain pathway is thought to play an important role in the regulation of the firing pattern in the ventral tegmental area (VTA) neurons. The understanding of the mechanisms that underlie the regulation of the midbrain dopamine neurons is critical to elucidate the reward system as well as certain pathological conditions such as drug addiction or schizophrenia. Descending prefrontal cortex (PFC) projections to the VTA have been primarily documented in the rodent brain (Maurice et al., 1999; Sesack and Carr, 2002). Furthermore, several anatomical studies based on the use of anterograde tracers in the nonhuman primate, have shown labeled fibers in the VTA that originated in the medial frontal cortex and anterior cingulate cortex (areas 25, 32 and 24), orbitofrontal cortex (areas 11 and 14) and dorsolateral prefrontal cortex (area 9 and 46) (Chiba et al., 2001; Frankle et al., 2006).
In order to complete the study of the direct inputs from the PFC to the VTA, the retrograde tracer 3% Fast Blue (FB) was placed in the mesencephalic ventral and dorsal tegmentum in Macaca fascicularis monkey, including the ventral tegmental area. We analyzed three cases injected with FB through a Hamilton syringe in the ventral mesencephalon. A magnetic resonance (MR) examination to localize the stereotaxic coordinates of the injection site was performed in all the animals used in this study. After 2 weeks survival, animals were deeply anesthetized and perfused through the heart with 4% paraformaldehyde. Several additional cases with 3H-aminoacid injections reported previously (Insausti and Amaral, 2008) were also available for analysis under dark field illumination.
Our preliminary results showed labeled neurons in the deep layers of principally, the medial frontal and orbitofrontal cortices, including areas 24, 32 and 25, and the orbitofrontal cortex (areas 11, 13, 12 and 14). Comparatively, the dorsolateral prefrontal (area 10, 9, 46 and 6) cortex displayed far fewer labeled neurons. Most of the labeled neurons were situated at the level of the medial part of caudal area 9 and rostral area 6.
The anterograde tracer experiments (5 cases with 3H-aminoacid deposits placed in the orbitofrontal cortex, and 3 cases in the medial frontal cortex) confirmed the existence of these projections, thus ruling out the contamination by fibers of passage at the retrograde tracer injection sites.
Our data suggest that the influence of medial frontal and orbitofrontal cortices on the dopaminergic ascending projections is much higher than from the dorsolateral prefrontal cortex.},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Ubero Martinez M{mubero}{Department Physiology of Cognitive Processes}, Mohedano-Moriano A, Munoz M, Arroyo-Jimenez MM, Marcos P, Artacho-Perula E, Hernandez-Mombiela D, Legidos-Garcia ME, Gonzalez-Fuentes J, Lagartos-Donate MJ, Cebada-Sanchez S, Amaral DG, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Insausti R}
}

@Poster{ BohrausLG2012,
title = {High-resolution CMRO2 in gray matter of macaque visual cortex},
year = {2012},
month = {10},
volume = {42},
number = {95.03},
abstract = {Commonly used fMRI signals measure local vascular and neural changes, with the former underlying a certain degree of spatiotemporal blurring. To minimize the latter, methods can be used that are less sensitive to partial volume effects. One such methodology capitalizes on high resolution, voxel-by-voxel CMRO2 measurements. Here we combined such measurements with so-called calibrated BOLD methodology to acquire CBF and BOLD maps during visual stimulation. Calibration was done by estimating a normalization factor (M) assessed in hypercapnia conditions, reflecting the upper limit of BOLD signal-changes. Quantitative description and interpretation of the data was done by using a model with parameters α, relating relative changes of CBV to CBF according to Grubb’s law (α=0.38), and β linking blood oxygenation to relaxivity (β=1.5). To improve the model, α was selected to account for changes in venous CBV only (α=0.23), i.e. to account for CBV-changes that are relevant to the BOLD signal, rather than to total CBV alterations. Alternatively, the model was compared to a more detailed model and showed highest accuracy with α=0.14 & β=0.91.
We determined the CMRO2 in anesthetized macaques at 7T & high resolution to separate the visually induced percent changes in CMRO2 (%CMRO2) in gray matter from white matter and vessel signals. We subsequently repeated the calculations using the aforementioned α & β parameters in order to reassess the robustness of the results. CBF and BOLD signals were acquired simultaneously with a triple-echo sequence. The %CMRO2 changes, M and n (ratio of fractional CBF to CMRO2) were calculated in V1 and V2. At a resolution of 1x1x3 mm3, the average %CMRO2 was 12±5% (mean ± sem) with M=0.29 ± 0.05. The coupling constant n was 2.1 ± 0.4. Similar values were obtained for α=0.23. The calibration constant M slightly increased using α=0.14 & β=0.91 but remained consistent with the value of 0.3-0.4 in gray matter at 7T. %CMRO2 changes & n were not very sensitive to the choice of parameters. For resolution of 0.5x0.5x3mm3 the results suggested higher %CMRO2 changes in gray matter than in white matter with a possible peak in layer IV, being the main input layer in macaque monkey. CBF and BOLD percent changes during visual stimulation and hypercapnic challenge were increased at a resolution of 0.5x0.5x3mm3 compared to 1x1x3 mm3.
In conclusion, using the calibrated BOLD method, we found high-resolution %CMRO2 changes of 12-14% and coupling ratios of 1.8-2.1, and demonstrated differences in %CMRO2 measured in gray and white matter. The reported results were found to be robust and insensitive to changes in the α & β parameters at high field.},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Bohraus Y{ybohraus}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Goense J{jozien}{Department Physiology of Cognitive Processes}}
}

@Poster{ NevesvLE2012,
title = {Locus coeruleus noradrenergic system mediates the transient cortical activation evoked by nociceptive stimulation},
year = {2012},
month = {10},
volume = {42},
number = {674.16},
abstract = {It is well-established that electrical or pharmacological activation of several nuclei in the reticular formation elicits cortical arousal which is reflected in the EEG as low amplitude and high frequency, or ‘desynchronized’, activity pattern. Among the ascending reticular activating system (ARAS) is the noradrenergic locus coeruleus (LC), which is critically involved in regulation of the sleep-wake cycle. Local activation of LC, as well as stimulation of its afferents, has been reported to induce cortical desynchronization. Interestingly, several nuclei of the ARAS have been shown to have either anatomical connections with LC or their activation showed impact on activity of LC neurons. Therefore, we hypothesized that the LC is a primary hub component in the ARAS. In order to test this hypothesis, we stimulated LC directly, by applying brief (100-200ms) trains of electrical pulses, or indirectly, by electrical stimulation of contralateral limb paw and simultaneously recorded local field potential (LFP) from multiple cortical and subcortical brain regions in urethane anesthetized rats. Both stimulation paradigms evoked transient (1-2 sec) desynchronization of the cortical LFP in all recorded sites, which were characterized by decreased LFP signal power within low frequency (1-8 Hz) and increased in high frequency range (>20 Hz). Foot shock evoked LFP desynchronization was completely abolished in all recording sites including the hid paw representation of the primary somatosensory cortex after bilateral, but not unilateral, selective inhibition of LC neurons by means of local iontophoretic injection of α2-agonist clonidine. Cortical desynchronization to nociceptive stimulation is used as an indicator of efficiency of analgesic treatment. Furthermore, clonidine is known to possess antinociceptive properties when used as additive in anesthetics. Therefore, our results demonstrate that LC is tightly involved in mediating nociception. The well-known antinociceptive property of α2-agonists in the peripheral nervous system is likely due to decreased levels of noradrenaline as result of the activation of presynaptic negative feedback of α2-receptors. The brain regions that mediate LC-dependent cortical desynchronization are yet to be identified.},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Neves RM{ricardo}{Department Physiology of Cognitive Processes}, van Keulen S{svankeulen}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}}
}

@Poster{ vanGrootelMMKMLK2012,
title = {Longitudinal fMRI study of cortical development in young monkeys},
year = {2012},
month = {10},
volume = {42},
number = {464.14},
abstract = {In typical adult visual processing, low-level visual features are integrated into a global construct that enables the recognition of an object. Behaviorally, young primates are impaired at integrating global form and motion cues. Also the neural machinery to support global processing is not fully developed. However, earlier studies using single-unit electrophysiology show that neuronal response properties are relatively mature compared to behavioral capability. Behavioral sensitivity to global stimuli continues to improve for months or years beyond the time that neuronal responses are adult-like. To understand this discrepancy, we used a larger scale method to investigate cortical development, functional MRI.
We tracked the development of BOLD activation in striate and extra-striate cortex of macaque monkeys (Macaca mulatta) longitudinally over 2-3 years. The animals were imaged at 4.7T while anesthetized and paralyzed. To segregate dorsal and ventral stream activity, we used stationary and dynamic Glass pattern stimuli. These have comparable local features (dipoles) but different global forms (concentric or radial) and responses were compared to random-dipole patterns having the same overall statistics. We analyzed responses to a variety of spatial and spatio-temporal stimuli using multi-voxel pattern analysis (MVPA). We determined how classification accuracy depended on the cumulative number of voxels from different cortical areas using a support vector machine (SVM). In young monkeys (age < 2 years), we observed high classification accuracies in primary visual cortex (V1) when Glass patterns were present or absent (stimulus vs. blank) but lower accuracy for static vs. dynamic patterns. Only 2/10 imaging sessions yielded accuracies significantly higher than chance for the same contrast in extrastriate area MT of young monkeys. These same comparisons consistently produced high classification accuracy in animals older than 2 years. These results indicate that BOLD signal differences can be measured at young ages with a Glass pattern stimulus. However, signals related to pattern type are not distinguished reliably until older ages. These results complement our earlier findings showing late onset of activation patterns in extrastriate cortex (Kourtzi et al., 2006, Mag Res Imaging).},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {van Grootel TJ{vangrootel}{Department Physiology of Cognitive Processes}, Meeson A, Munk MHJ{munk}{Department Physiology of Cognitive Processes}, Kourtzi Z{zoe}{Department Physiology of Cognitive Processes}, Movshon JA, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kiorpes L{kiorpes}{Department Physiology of Cognitive Processes}}
}

@Poster{ KleinEPBLS2012,
title = {Optogenetics in the macaque thalamus},
year = {2012},
month = {10},
volume = {42},
number = {610.09},
abstract = {Optogenetics is a potentially powerful tool to manipulate and map specific neural circuits. The few studies that have so far implemented this method in primates focused on the neocortex. Here, we transduced cells in multiple thalamic nuclei of one rhesus macaque with a DNA construct encoding the microbial proton-pump ArchT and the green fluorescent protein (GFP). A constitutively active promoter (CAG) was used to ensure high-level protein expression. Adeno associated virus (AAV2 or AAV5) was used to deliver the gene.
Electrophysiological recordings were carried out under anesthesia six to eight weeks after the AAV injections. Continuous illumination with green light (532 nm) through an optic fiber (110 µm diameter) placed in the injected thalamic regions markedly and reliably reduced the local ongoing spiking activity (60% on average) with fast recovery to baseline firing after light offset.
Post-mortem stereological microscope examination indicated that ~25% of the neurons in the thalamic injection sites were GFP-labeled and exhibited the typical large soma size and radial dendritic arborization characteristic of thalamocortical projection (TC) neurons. We also found dense GFP-labeled axon terminals in layers 3-4 in the cortical targets of the injected thalamic regions. In the TC soma, the GFP labeling was mostly localized at membrane sites with no accumulation in the cytoplasm and cell nucleus. Based on morphological analysis there was no obvious GFP labeling in local interneurons or in the glia. However, besides the apparently healthy TC neurons, we also observed a small percentage (~5%) of round GFP-labeled formations that had roughly the same diameter as the TC dendrite arborization (~85 µm) but no recognizable neuropil or perikaryal morphology. These formations could be the remains of cells that degenerated after overexpressing the construct.
These results show that AAV vectors can be used in the monkey thalamus for intra-neuronal delivery of opsin-encoding DNA sequences and reliable manipulation of neuronal activity. While further characterization of the extent and specificity of gene expression is necessary, intrathalamic injections of AAV vectors could provide the much-needed tool to examine separately and in great physiological and anatomical detail the intricately mingled components of the primate thalamocortical circuitry.},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Klein C{cklein}{Department Physiology of Cognitive Processes}, Evrard HC{evrard}{Department Physiology of Cognitive Processes}, Power AT{apower}{Department Physiology of Cognitive Processes}, Boyden ES, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Schmid M{mschmid}}
}

@Poster{ PerrodinKLP2012,
title = {Visual influences on neurons in voice-sensitive cortex},
year = {2012},
month = {10},
volume = {42},
number = {366.18},
abstract = {The brains of human and nonhuman primates are thought to contain brain regions that have specialized for processing voice and face content. Although voice- and face-sensitive regions have been primarily studied in their respective sensory modalities, recent human functional magnetic resonance imaging (fMRI) studies have suggested that cross-modal interactions occur in these regions. Here, we investigated whether, and how, neuronal spiking activity in a voice region is modulated by visual (face) stimulation.
Using fMRI-guided electrophysiology, we targeted neurons in a voice-sensitive region in the right supra-temporal plane of two rhesus macaques. We used dynamic faces and voices for stimulation, including congruent and incongruent audiovisual pairs. Different stimuli by monkey and human callers were organized in a multifactorial design, to analyze the impact of the following factors on neuronal audiovisual influences: caller species, familiarity, and identity, and call type.
Within this voice-sensitive region, we obtained recordings from 149 auditory responsive units, 45% of which demonstrated visual influences. The majority of the visual modulation was characterized by audiovisual responses that significantly deviated from the sum of the responses to both unimodal stimuli (i.e., non-additive multisensory influences). Contrasting monkey ‘coo’ calls with human-mimicked ‘coos’ revealed qualitatively similar, but quantitatively different audiovisual processing of conspecific relative to heterospecific voices; human calls elicited more sub-additive interactions than monkey calls. The call type and speaker identity factors interacted and significantly impacted upon both the direction and amplitude of the visual influences. Finally, familiar voices consistently elicited stronger audiovisual influences than unfamiliar voices, despite auditory responses being similar. Lastly, we compared the specificity of audiovisual interactions and the reliability of neuronal responses across congruent and incongruent audiovisual pairs. In some cases, we found neurons to be differentially affected by voice-face congruency, e.g., neurons were most sensitive to violating the congruency of a conspecific voice/face pairing as caused by substituting the monkey face with a human face.
In conclusion, our study links to human fMRI studies on cross-sensory influences in voice/face regions, and the results describe the nature of the visual influences on neuronal responses in a voice-sensitive region in the primate brain. The results also help to characterize the stimulus feature-dependent influences on the cross-modal effects into this region.},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Perrodin C{cperrodin}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Petkov CI{chrisp}}
}

@Poster{ KleinEPBLS2012_2,
title = {Optogenetics in the macaque thalamus},
year = {2012},
month = {10},
web_url = {http://www.brainresearchconference.com/},
event_name = {7th Brain Research Conference “Optogenetics and Pharmacogenetics in Neuronal Function and Dysfunction”},
event_place = {New Orleans, LA, USA},
state = {accepted},
author = {Klein C{cklein}{Department Physiology of Cognitive Processes}, Evrard HC{evrard}{Department Physiology of Cognitive Processes}, Power AT{apower}{Department Physiology of Cognitive Processes}, Boyden ES, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Schmid MC{mschmid}}
}

@Poster{ LiFLK2012,
title = {Multi-Stable Visual Motion Perception},
journal = {Frontiers in Computational Neuroscience},
year = {2012},
month = {9},
volume = {Conference Abstract: Bernstein Conference 2012},
pages = {190},
abstract = {Perceptual multi-stability is established when the brain fails to reach a single interpretation of the input from the external world. This issue intrigued scientific minds for more than two hundred years. This phenomenon has been found in vision (Leopold & Logothetis, 1999), audition (Repp, 2007), olfaction (Zhou & Chen, 2009) and speech (Warren & Gregory, 1958). Crucial features are similar within and across modalities (Schwarts et al., 2012).
In the visual modality, a number of ambiguous visual patterns have been described such as the Necker cube, motion plaids, and binocular rivalry. Multi-stable stimuli can provide unique insights into visual processing, as changes in perception are decoupled from changes in the stimulus. Understanding of how multi-stable perception occurs might help one to understand visual perception in general.

A key question in multi-stable perception is what the brain processes are responsible in the identification and alternation of the percepts. Some investigators suggest that both top-down and bottom-up processes are involved (García Pérez, 1989) but others argue that multi-stable perception does not need high-level processing but happens automatically as low-level competition between the stimulus features (Akman et al., 2009; Wilson et al, 2000). Furthermore, it is well known that changes in stimulus features can bias perception in one or another direction, (Klink, et al., 2012).

In order to explore this question, we used multi-stable motion stimuli and specifically moving plaids consisting of three superimposed gratings moving in equidistant directions (difference of 120 deg). These stimuli induce the perception of component and pattern motion simultaneously since any two component gratings bind together and are perceived to move in the opposite direction of the third grating component. We modulated properties of the stimuli such as grating speed and size and recorded the responses of human subjects reporting the direction of the single grating using one of three buttons for each direction. Preliminary results show that perceptual dominance is greatly affected by the selection of grating speeds. Grating size did not greatly change the predominance of the different gratings. We find that gratings with speed closer to physiological values have greater probability to be perceived and that gratings with similar speeds tend to group more often than gratings with different speeds. Further manipulations of other stimulus features like contrast and spatial frequency allow parametric variations of the relative probabilities of different interpretations. Our future goal is to use this information to built models of perceptual alternations using probabilistic inference.},
web_url = {http://www.frontiersin.org/10.3389/conf.fncom.2012.55.00058/event_abstract},
event_name = {Bernstein Conference 2012},
event_place = {München, Germany},
state = {published},
DOI = {10.3389/conf.fncom.2012.55.00058},
author = {Li Q{qinglinli}{Department Physiology of Cognitive Processes}, Fleming RW{roland}{Department Human Perception, Cognition and Action}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Keliris GA{george}{Department Physiology of Cognitive Processes}}
}

@Poster{ SmirnakisKSPL2012,
title = {Population receptive field measurements in macaque visual cortex},
journal = {Journal of Vision},
year = {2012},
month = {8},
volume = {12},
number = {9},
pages = {1397},
abstract = {Visual receptive fields have dynamic properties that may change with the conditions of visual stimulation or with the state of chronic visual deprivation. We used 4.7 Tesla functional magnetic resonance imaging (fMRI) to study the visual cortex of two normal adult macaque monkeys and one macaque with binocular central retinal lesions due to a form of juvenile macular degeneration (MD). FMRI experiments were performed under light remifentanyl induced anesthesia (Logothetis et al. Nat. Neurosci. 1999). Standard moving horizontal/vertical bar stimuli were presented to the subjects and the population receptive field (pRF) method (Dumoulin and Wandell, Neuroimage 2008) was used to measure retinotopic maps and pRF sizes in early visual areas. FMRI measurements of normal monkeys agree with published electrophysiological results, with pRF sizes and electrophysiology measurements showing similar trends. For the MD monkey, the size and location of the lesion projection zone (LPZ) was consistent with the retinotopic projection of the retinal lesion in early visual areas. No significant BOLD activity was seen within the V1 LPZ, and the retinotopic organization of the non-deafferented V1 periphery was regular without distortion. Interestingly, area V5/MT of the MD monkey showed more extensive activation than area V5/MT of control monkeys which had part of their visual field obscured (artificial scotoma) to match the scotoma of the MD monkey. V5/MT PRF sizes of the MD monkey were on average smaller than controls. PRF estimation methods allow us to measure and follow in vivo how the properties of visual areas change as a function of cortical reorganization. Finally, if there is time, we will discuss a different method of pRF estimation that yields additional information.},
web_url = {http://www.journalofvision.org/content/12/9/1397.abstract},
event_name = {12th Annual Meeting of the Vision Sciences Society (VSS 2012)},
event_place = {Naples, FL, USA},
state = {published},
author = {Smirnakis SM, Keliris GA{george}{Department Physiology of Cognitive Processes}, Shao Y{yshao}{Department Physiology of Cognitive Processes}, Papanikolaou A{amalia}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ BahmaniLK2012,
title = {The role of parietal visual cortex in perceptual transitions during bistable perception},
journal = {Journal of Vision},
year = {2012},
month = {8},
volume = {12},
number = {9},
pages = {683},
abstract = {Several imaging studies in humans have shown the involvement of a frontoparietal network of cortical areas in perceptual transitions during bistable perception. To investigate further the possible role of parietal visual areas in perceptual alternations, we recorded extracellular neural activity in the lateral intraparietal area (LIP) of the rhesus macaque. The subject was initially presented with congruent patterns to the two eyes. Then the stimulus was switched for either one or both eyes (binocular flash suppression versus physical alternation), both resulting in perception of the newly presented stimulus. The recorded cells typically showed an initial burst of activity at stimulus onsets as well as stimulus switches. In contrast to previous reports by a number of fMRI studies, we found strong transient activity during physical alternations at the single cell level. This signal was also present during binocular flash suppression but to a lesser extent. Importantly, the amplitude of the signal dropped substantially in control conditions where physical changes were introduced in the stimuli but did not induce concomitant changes in perception. The transient response of the recorded neurons was followed by a tonic response which exhibited independent dynamics. Interestingly, this sustained activity was significantly lower during incongruent versus congruent stimulation. We conjecture that areas at the high end of the dorsal pathway might be involved in multistable perception in a different way in comparison with feature and object selective areas of the ventral pathway. The transient signal recorded in LIP neurons during perceptual transitions could potentially trigger reorganization of activity in constellations of feature selective neurons in the ventral pathway. In addition, the suppression of the sustained activity in LIP during incongruent stimulation may reflect inhibitory processes involved in the resolution of conflict between the two stimuli or indicate a failure to bind the sensory input into a coherent percept.},
web_url = {http://www.journalofvision.org/content/12/9/683.abstract},
event_name = {12th Annual Meeting of the Vision Sciences Society (VSS 2012)},
event_place = {Naples, FL, USA},
state = {published},
author = {Bahmani H{hbahmani}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Keliris GA{george}{Department Physiology of Cognitive Processes}}
}

@Poster{ EvrardFL2012_3,
title = {Areal Distribution Of The Von Economo In The Anterior Insular And Anterior Cingulate Cortices In The Macaque Monkey},
year = {2012},
month = {7},
volume = {8},
number = {p136.23},
abstract = {The anterior insular (AIC) and anterior cingulate (ACC) cortices and their unique spindle-shaped von Economo neurons (VENs) emerged within the last decade as having a potentially major role in interoceptive, emotional and social awareness and cognition in humans. A role of the VENs in these fundamental phenomena is supported by their selective depletion in highly detrimental neuropsychiatric diseases characterized by a loss of self-conscious emotion and empathy and by a lack of appropriate behavioral response in emotionally-salient situations. The much-needed invasive examination of the VENs in the laboratory has been limited so far by the assumption that this neuron occurs among primates exclusively in humans and great apes. In a recent contribution, we demonstrated the presence of VENs in the agranular anterior insula and ACC in two species of macaque monkeys (rhesus and cynomolgus) typically used in the laboratory. VENs were also found in the same regions in a broad range of monkeys and in lesser apes. In the present contribution, we demonstrate that VENs in the macaque occur in an architectonically distinct area of the agranular anterior insula, namely ´Ia5´, and in several distinct areas in ACC and in the medial wall of the prefrontal cortex. This specific areal distribution of the VENs suggests that their developmental fate is bound to the overall plan of development and parcellation of the cerebral cortex in primates. It also offers a unique opportunity to examine the primal function and connections of the VENs on the basis of what is already known about these areas in the macaque monkey. Such examination could provide significantly new and valuable information on the possible role of the VENs in human self-awareness, social cognition and related neuropsychiatric disorders.},
web_url = {http://fens.ekonnect.co/FENS_331/poster_35097/program.aspx},
event_name = {8th Forum of European Neuroscience (FENS 2012)},
event_place = {Barcelona, Spain},
state = {published},
author = {Evrard HC{evrard}{Department Physiology of Cognitive Processes}, Forro T{tforro}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ DianaMMAPMULFLCLI2012,
title = {Brainstem Afferents To The Hippocampal Formation: Comparative Inmunohistochemical Study In The Macaca Fascicularis Monkey},
year = {2012},
month = {7},
volume = {8},
number = {p159.08},
abstract = {The neuroanatomical connections in the nonhuman primate of the brainstem structures to the Hippocampal Formation (HF, which includes the dentate gyrus -DG-, CA3, CA2, CA1, subiculum, pre-parasubiculum and the entorhinal cortex -EC-) are still unclear. Previous tracer studies in nonhuman primates show retrogradely labeled neurons in the brainstem including the Ventral Tegmental Area (VTA), Locus Coeruleus (LC) and Raphe Nuclei (RN), after deposits in the hippocampus (Amaral and Cowan, 1980), as well as in the EC (Insausti et al., 1987). In order to characterize the neurotransmitters associated to those projections (presumably dopaminergic -DA, VTA-, noradrenergic -NA, LC-, and serotoninergic -5-HT, RN-, respectively), and the topographic and laminar differences, we studied comparatively the innervation in the HF using immunohistochemical techniques.
Inmunohistochemistry for DA (Tirosine Hidroxilase, TH), NA (Dopamine Beta Hidroxilase, DBH), and 5-HT showed: a) The DG molecular layer had TH-immunoreactive fibers, while the polymorphic layer contained positive 5-HT fiber labeling, b) CA3 pyramidal layer showed denser 5-HT labeling than TH, c) CA1 had scattered TH and 5-HT fibers, d) The superficial layer of the rostral EC (I and II) had TH- and 5-HT-labelled processes, e) TH and DBH positive cells were primarily found in the lateral subdivisions of the EC (ELR/ELc). The preferential location of these positive fibers in ELR/ELc, is significant, as this portion of the EC receives abundant unimodal and polymodal sensory input and innervates the body and tail of the hippocampus, and therefore it might be a crucial link in the consolidation of memory through the monoaminergic modulation of the HF.},
web_url = {http://fens.ekonnect.co/FENS_331/poster_35737/program.aspx},
event_name = {8th Forum of European Neuroscience (FENS 2012)},
event_place = {Barcelona, Spain},
state = {published},
author = {Diana H, Munoz M, Marcos P, Arroyo-Jimenez MDM, P{\'e}rula E, Mohedano-Moriano A, Ubero MDM{mubero}{Department Physiology of Cognitive Processes}, Legidos-Garcia ME, Fuentes J, Lagartos MJ, Cebada S, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Insausti R}
}

@Poster{ vanKeulenLE2012,
title = {Differential Noradrenergic Modulation Of Sensory Processing In The Rat Somatosensory And Prefrontal Cortex},
year = {2012},
month = {7},
volume = {8},
number = {p131.15},
abstract = {Alerting sensory stimuli activate the nucleus Locus Coeruleus (LC) and the associated release of Noradrenaline (NE) improves sensory signaling. We compared the LC-mediated modulation of sensory responses in the primary sensory cortex (S1) and the medial prefrontal cortex (mPFC), a higher integrative cortical region. We performed recordings in S1, mPFC, and LC in response to mild electrical foot shocks (0.5ms, 5mA) and manipulated the activity level of LC-NE system by clonidine, an alpha2-receptor agonist, in the urethane-anesthetized rat. We used systemic and local (in LC) application of clonidine, both leading to decreased level of NE in the brain. Iontophoretic application of clonidine (50nA, 50µl/ml, 20min) into LC resulted in complete cessation of both spontaneous and evoked activity of LC-NE neurons. Systemic clonidine injection (50 µl/ml,i.p.) produced a decrease in LC spontaneous firing, however the LC sensory responses were preserved. The short-latency (~17ms) evoked responses in S1 were minimally affected by clonidine, while late response component (~336ms) was decreased. In contrast, bi-directional changes were observed in mPFC. The response amplitude of mPFC neurons was substantially decreased following both local and systemic clonidine administration. Conversely, proportion of initially non-responsive mPFC neurons became responsive following local (22% of neurons) or systemic (38%) clonidine application. The LFPs displayed regular slow (~1Hz) oscillations that are characteristic for synchronized cortical state induced by anesthesia. Sensory stimulation evoked transient (~1s) periods of desynchronized (activated) state in 58% of cases, which were abolished by local (60% of cases) and systemic (75%) injection of clonidine. The latter effect strongly correlated with a degree of LC inhibition by clonidine. Thus, LC-NE system is critically involved in shifting cortical activity to desynchronized state that is beneficial for sensory processing. Overall, while NE effects were observed in both cortical regions, our results indicate that mPFC receives a stronger NE neuromodulatory input.},
web_url = {http://fens.ekonnect.co/FENS_331/poster_34966/program.aspx},
event_name = {8th Forum of European Neuroscience (FENS 2012)},
event_place = {Barcelona, Spain},
state = {published},
author = {van Keulen S{svankeulen}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}}
}

@Poster{ vonPfostlZLVZLR2012,
title = {Electrophysiological Effects Of Lactate On Primary Visual Cortex Of Non-Human Primates},
year = {2012},
month = {7},
volume = {8},
number = {p140.27},
abstract = {Recent evidence suggests that increased metabolic demand of neurons can be met by lactate, a metabolite of glucose. In addition, during neuronal activation lactate production in the brain is increased. We already demonstrated that this physiological formation of lactate can contribute to the BOLD signal. Here we set out to determine the underlying mechanism that drives the observed increase in BOLD baseline. This effect could be explained by an increase in CBF or also increased neuronal activity. The influence of lactate on cerebral blood flow has been already established. To test if lactate has also an effect on neuronal activity we performed electrophysiological recordings in V1 of anesthetized non-human primates. Lactate was applied slow and continuously (0.04 mmol/kg/min). This infusion induced a significant increase in local field potential (LfpH, 24-90 Hz) power and visual stimulus induced modulation. An average increase of 23.0±1.2% and 76.0±20% was recorded for power and modulation of LfpH respectively; this effect reached significance 4.8±3.1 min after the start of the injection and lasted for 19.5±5.0 min. The timing of the effects is comparable to the timing of the BOLD signal increase evoked by the same infusion protocol of lactate. In the multiunit activity (MUA, 400-3000 Hz) no significant effect was observed. In summary, by applying lactate, a potential fuel for activated neurons, we increase LfpH power and modulation but not the spiking activity. Since LfpH is a reliable driver of the BOLD signal at least part of the lactate effect on the BOLD signal can be explained by an increase in neuronal activity.},
web_url = {http://fens.ekonnect.co/FENS_331/poster_35355/program.aspx},
event_name = {8th Forum of European Neuroscience (FENS 2012)},
event_place = {Barcelona, Spain},
state = {published},
author = {von Pf\"ostl V{vpfoestl}{Department Physiology of Cognitive Processes}, Zaldivar D{dzaldivar}{Department Physiology of Cognitive Processes}, Li J{juan}{Department Physiology of Cognitive Processes}, Viswanath S{sviswanath}{Department Physiology of Cognitive Processes}, Zhang X{xiaozhe}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rauch A{arauch}{Department Physiology of Cognitive Processes}}
}

@Poster{ UberoMartinezMAMMAHLLI2012,
title = {Hippocampal Formation Projection To Ventral Tegmental Area: An Anatomical Study In The Non-Human Primate},
year = {2012},
month = {7},
volume = {8},
number = {p069.14},
abstract = {The Hippocampal Formation (HF) has a critical role in episodic memory. One of the major components in episodic memory is the encoding of novel stimuli, which is associated to dopaminergic system. Lisman and Grace (2005) proposed that novelty signals in the hippocampus modulate the activity of dopaminergic neurons in the ventral tegmental area (VTA) and that, via a feedback loop, the increase of dopamine in hippocampal neurons promotes the encoding for the novel event.
Retrograde tracer studies have demonstrated that the VTA projects directly to the HF in primates (Amaral and Cowan, 1980; Insausti et al., 1987) as well as in rodents. However, whether these projections are reciprocal or not is unknown. Despite this lack of evidence of a direct projection, functional studies indicate that the dopaminergic neurons of the VTA are strongly influenced by the hippocampus indirectly through either lateral septum (Luo et al. 2011) or nucleus accumbens-ventral pallidum pathways (Lisman and Grace 2005).
In order to determine the existence of direct inputs from the HF to the VTA and which are the specific fields within the HF responsible of the projection, the retrograde tracers were placed in the mesencephalic ventral and dorsal tegmentum of the Macaca fascicularis monkey, including the VTA. The retrograde cell labeling was analyzed with an epifluorescence microscope coupled to a computerized charting system. Our preliminary results showed scarce labeled cells in the HF, specifically in dorsal subiculum, and deep layers of the caudomedial portion of the entorhinal cortex (subfield EO and medialmost EI). These results clarify the functional HF-VTA loop playing a role in learning and memory, and different neuropsychiatric diseases (schizophrenia, Alzheimer´s and Parkinson's disease.},
web_url = {http://fens.ekonnect.co/FENS_331/poster_33135/program.aspx},
event_name = {8th Forum of European Neuroscience (FENS 2012)},
event_place = {Barcelona, Spain},
state = {published},
author = {Ubero Martinez MDM{mubero}{Department Physiology of Cognitive Processes}, Mohedano Moriano A, Arroyo Jimenez MDM, Munoz M, Marcos P, Artacho Perula E, Hernandez Mombiela D, Legidos Garcia ME, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Insausti R}
}

@Poster{ NovitskayaLE2012,
title = {Noradrenergic Modulation Of Cortical And Hippocampal Activity During Natural Sleep In Rats},
year = {2012},
month = {7},
volume = {8},
number = {p052.2},
abstract = {The activity of noradrenergic (NA) neurons of the brain stem neuromodulatory nucleus Locus Coeruleus (LC) fluctuates across sleep/wake cycle; LC firing being highest during awake, substantially decreased during slow-wave sleep (SWS) and essentially absent during REM. Due to reduced level of NA during sleep, little attention has been given to the NA modulation of sleep-associated brain rhythms. We recently reported that LC firing is tightly related to the cortical slow oscillations in naturally sleeping rats. Psychiatric disorders, which are characterized by enhanced activity of NA system, are often accompanied by sleep disturbances. Neurophysiological mechanisms underlying this phenomenon remain unknown. The present study aimed to characterize changes in cortical and hippocampal activity produced by increased tonic firing of LC during sleep. Extracellular electrophysiological recordings in cortex and hippocampus were made using linear electrode arrays. The LC activity was modulated by electrical microstimulation via chronically implanted electrode in LC. Trains of pulses (100-500ms, 20-100Hz) were delivered to the LC unilaterally at the onset of SWS every 10s continuously for 10 min. None of the stimulation parameters resulted in behavioral waking up or any visible discomfort of the animal. The LC stimulation with relatively long (50Hz, 500ms) trains of pulses or high-frequency LC stimulation with relatively short trains (100Hz, 100ms) immediately reduced slow wave (1-4Hz) and sigma (12-15Hz) activity in cortex. It resulted in complete elimination of the sleep spindles, characteristic for normal SWS. The slow activity in hippocampus was also strongly affected by LC stimulation. The effect of a single train lasted for up to 6 sec until recovery of neural activity to the baseline level. Our results demonstrate that a mildly elevated LC activity affects a microstructure of the sleep pattern, as indicated by electrophysiological correlates of sleep, without influencing the sleep/awake cycle or inducing behavioral arousal.},
web_url = {http://fens.ekonnect.co/FENS_331/poster_32696/program.aspx},
event_name = {8th Forum of European Neuroscience (FENS 2012)},
event_place = {Barcelona, Spain},
state = {published},
author = {Novitskaya Y{ynovitskaya}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}}
}

@Poster{ AzevedoALR2012,
title = {Responses Of Neurons In The Nucleus Basalis To Visual Stimuli Differing In Their Familiarity, Category And Coherence},
year = {2012},
month = {7},
volume = {8},
number = {p039.28},
abstract = {The nucleus basalis of Meynert (NBM) provides all non-intrinsic cholinergic input to the neocortex. It has been implicated in signal detection and in cortical plasticity. Previous studies have proposed that NBM neurons respond differentially to certain characteristics of a stimulus, such as its familiarity. However, one possible explanation is that the expected reward or other arousal value of the visual stimulus and not familiarity would account for such response selectivity. To test this hypothesis, we tested two monkeys (Macaca mulatta) with visual stimuli presented at the centre of fixation while they performed a fixation task. Single electrodes and tetrodes were implanted in the NBM and the visual responses of single neurons and neuronal ensembles were recorded while three image parameters were changed:
1) familiarity/novelty,
2) image category (monkeys or flowers) and
3) coherence (salience).
In all these cases all stimuli had an equal chance of receiving a reward. We selected neurons that had visual responses that exceeded two standard deviations from the spontaneous activity for at least some stimuli for a statistical analysis. Quantification of the response selectivity of these nucleus basalis neurons using a measure of sparseness indicated that they had little selectivity for any of the three factors employed: stimulus novelty, category or coherence. All responsive neurons responded to all types of stimuli employed, including to non-coherent stimuli consisting of white visual noise. This result favours the hypothesis that the determining factor in the responses of nucleus basalis neurons is the association of a stimulus with reward.},
web_url = {http://fens.ekonnect.co/FENS_331/poster_32342/program.aspx},
event_name = {8th Forum of European Neuroscience (FENS 2012)},
event_place = {Barcelona, Spain},
state = {published},
author = {Azevedo FAC{fazevedo}{Department Physiology of Cognitive Processes}, Aggelopoulos NC{aggelopoulos}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ ZaldivarLvWGRL2012,
title = {The Modulatory Role Of Dopamine In The Early Visual System Of Macaques Investigated By Fmri, Neurochemistry And Neurophysiology},
year = {2012},
month = {7},
volume = {8},
number = {p063.19},
abstract = {The presence of dopamine-(DA)-receptors-(DARs) and innervations in early sensory pathways has previously been demonstrated in monkeys and humans. Nonetheless, their possible role in the sensory processing is still far from being understood. Anatomical evidence has shown that DARs are expressed in early-visual-system. These studies indicated that D1Rs are found in primary-visual-cortex, while D2Rs are predominantly expressed in the lateral-geniculate-nucleus-(LGN). D1Rs have a facilitating effect on neuronal processing whereas D2Rs show a dampening effect. Given their differences in anatomical distribution and functionality the two kinds of DARs may have a differential effect on thalamocortical information transfer. Here, we set out to investigate DAergic impact on V1 by using combined fMRI, neurophysiology and neurochemistry measurements in anesthetized non-human-primates, during systemic-application of L-DOPA-Carbidopa (2.1/0.5mg/kg, respectively). Our results show that the stimulus-induced modulation of the BOLD-signal decreases by 40±5% for 10±3min (n=8,p < 0.05). This decrease is concomitant with an improvement in the signal-to-noise-ratio-(SNR) in multi-unit-activity-(MUA: 900-3200Hz) as well as in the CV (p< 0.05) of the theta (4-8Hz), low-gamma (20-60Hz) and gamma (65-120Hz) bands of LFP. In contrast, local application of DA in V1 did not induce any changes in neuronal activity indicating that the observed effects are most probably mediated by D2Rs of LGN. DAergic neuromodulation decreased the SNR of the neuronal recordings in V1 which reflects a sparse and dampened firing pattern. Neurochemical sampling in V1 has shown an increased glutamate/GABA-ratio which might reflect a change in the excitation/inhibition balance induced by DA. The additional measured lactate/pyruvate-ratio has also shown a change indicating a decreased metabolic demand. These findings suggest that the visual inputs are attenuated by the local DAergic-circuitry of LGN (D2Rs) generating sparse and precise neuronal firing in V1. At the same time, however, the reduced mass-activity appears to reduce the energy demands, and the stimulus-induced-modulation of the BOLD-signal.},
web_url = {http://fens.ekonnect.co/FENS_331/poster_33040/program.aspx},
event_name = {8th Forum of European Neuroscience (FENS 2012)},
event_place = {Barcelona, Spain},
state = {published},
author = {Zaldivar D{dzaldivar}{Department Physiology of Cognitive Processes}, Li J{juan}{Department Physiology of Cognitive Processes}, von Pf\"ostl V{vpfoestl}{Department Physiology of Cognitive Processes}, Whittingstall K{kevin}{Department Physiology of Cognitive Processes}, Goense J{jozien}{Department Physiology of Cognitive Processes}, Rauch A{arauch}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ PerrodinKLP2012_2,
title = {Visual Influences On Neurons In Voice-Sensitive Cortex},
year = {2012},
month = {7},
volume = {8},
number = {p038.23},
abstract = {Many animals use cross-sensory information during communication, but it remains unclear how the brain integrates face and voice information. Functional imaging evidence suggests that the brains of human and nonhuman primates contain voice- and face-sensitive regions, and some of the human studies have suggested that multisensory interactions occur in these regions. Yet, to date neurons in monkey voice/face regions have been studied exclusively with unisensory stimuli.
We targeted neurons in a recently identified voice-sensitive cluster in the right hemisphere on the supratemporal plane to investigate how neurons in the monkey brain combine auditory voice and visual face information. Extracellular recordings were conducted in two Rhesus macaques participating in a visual fixation task. Dynamic face and voice stimuli (movies of vocalizing monkeys and humans imitating monkey “coo” calls) were presented in auditory only, visual only and audio-visual stimulation conditions, including congruent and incongruent audio-visual pairs. In this region, we identified spiking activity driven by the presence of auditory stimuli (n = 130 single- and multi-units), 42% of which demonstrated visual influences. Most of the visual modulation (36% of responsive units) consisted of nonadditive multisensory effects, where the audiovisual responses significantly deviated from the sum of both unimodal responses. The magnitude of the visual influences was differentially sensitive to stimulus features such as call type, speaker identity and familiarity. Human voices elicited qualitatively similar auditory and audiovisual responses as monkey voices. Finally, we found that incongruent stimuli elicited a larger proportion of sublinear audiovisual interactions, relative to congruent audiovisual pairs.
Our results identify visual influences at the neuronal level in a primate auditory 'voice' region. Together, with results from functional imaging studies in humans, these findings extend our understanding of the multisensory influences at voice regions, which might also be evident in neurons at face-sensitive regions.},
web_url = {http://fens.ekonnect.co/FENS_331/poster_32304/program.aspx},
event_name = {8th Forum of European Neuroscience (FENS 2012)},
event_place = {Barcelona, Spain},
state = {published},
author = {Perrodin C{cperrodin}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Petkov CI{chrisp}}
}

@Poster{ MamedovEHEL2012,
title = {Development of multimodal imaging probes for neuroanatomical connectivity studies in vivo by means of MRI},
year = {2012},
month = {5},
volume = {20},
number = {1632},
abstract = {A Gd3+ based paramagnetic dextran conjugate has been developed, which enables the tracking of neuroanatomical connectivity in the brain by both MR and optical imaging. Cell studies demonstrated that the synthesized tracer was efficiently internalized into neuronal cells and transported toward the axons. Furthermore, our preliminary in vivo experiments revealed efficient transportation of the conjugate, thereby proving its applicability for neuroanatomical studies by T1-weighted MRI. Initial in vivo experiments in rodents demonstrated the significant potential of this method.},
web_url = {http://www.ismrm.org/12/},
event_name = {20th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2012)},
event_place = {Melbourne, Australia},
state = {published},
author = {Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, Engelmann J{joern}{Department High-Field Magnetic Resonance}, Hagberg G{ghagberg}{Department High-Field Magnetic Resonance}, Eschenko O{oeschenko}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ CavusogluBU2012,
title = {Retinotopic maps and hemodynamic delays in the human visual cortex measured using arterial spin labeling},
year = {2012},
month = {5},
volume = {20},
number = {578},
web_url = {http://www.ismrm.org/12/Session57.htm},
event_name = {20th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2012)},
event_place = {Melbourne, Australia},
state = {published},
author = {Cavusoglu M{mustafa}{Department High-Field Magnetic Resonance}, Bartels A{abartels}{Department Physiology of Cognitive Processes} and Uludag K{kuludag}{Department High-Field Magnetic Resonance}}
}

@Poster{ GoenseML2012,
title = {Stimulus dependent laminar differences in functional CBF in monkey V1},
year = {2012},
month = {5},
volume = {20},
number = {0718},
abstract = {The relative contributions of excitation and inhibition to fMRI responses remain unknown. In principle, inhibition may increase or decrease fMRI signals depending on local circuitry. Negative BOLD signals and CBF decreases were shown for ring stimuli in primary visual cortex (V1). High-resolution fMRI can exploit the functional segregation in V1 to reveal differences between excitatory and inhibitory responses, including layer-specific differences. We measured high-resolution BOLD, CBV and CBF in macaque V1 and found laminar differences in the positive and negative fCBF responses, suggesting different neurovascular coupling mechanisms depending on the location within the cortical sheet.},
web_url = {http://www.ismrm.org/12/},
event_name = {20th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2012)},
event_place = {Melbourne, Australia},
state = {published},
author = {Goense J{jozien}{Department Physiology of Cognitive Processes}, Merkle H{hellmut} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ BesserveBPCKTPL2012,
title = {Identifying endogenous rhythmic spatio-temporal patterns in micro-electrode array recordings},
year = {2012},
month = {2},
volume = {9},
pages = {114-115},
abstract = {Microelectrode arrays are a privileged recording modality to study neural processes with a very fine spatial and
temporal resolution. They capture the activity of small populations and permit assessment of synergistic interactions
between cells. Patterns of rhythmic ongoing activity are of particular interest because they reflect the
intrinsic dynamics of neural populations and the way such dynamics may optimize the processing of incoming
information. In this study, we identify the various coherent spatio-temporal patterns of rhythmic activity occurring
across time using a two steps approach. First, signals were bandpass filtered in a relevant frequency band and
subsequently Hilbert-transformed. Second, the complex patterns of activity occurring across time were clustered
using a graph cut algorithm based on a phase shift invariant similarity measure. This invariance is a key-property
of our approach to isolate wave propagation phenomena. We apply our method to Local Field Potentials recorded
in the inferior convexity of the Prefrontal Cortex (icPFC) in two anesthetized macaques using a multi electrode array.
We found a dominant travelling wave pattern in the beta band (15-25Hz), propagating along the ventral-dorsal
plane, emerging and vanishing across time both in the absence of visual stimulation (spontaneous activity) and
during binocular stimulation with movie clips. By computing mutual information, we showed that the amplitude of
this wave actually carries sensory information during the presentation of several movies. Altogether, our analysis
provides evidence for travelling wave phenomena reflecting the distributed computation in icPFC, which is known
to be involved in higher order sensory processing. More generally, our approach enables the unsupervised analysis
of the complex spatio-temporal neural dynamics in ongoing signals, providing key information to understand
cooperative mechanisms in spatially distributed neural populations.},
web_url = {http://www.cosyne.org/c/index.php?title=Cosyne_12},
event_name = {9th Annual Computational and Systems Neuroscience Meeting (Cosyne 2012)},
event_place = {Salt Lake City, UT, USA},
state = {published},
author = {Besserve M{besserve}{Department Empirical Inference}{Department Physiology of Cognitive Processes}, Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Crocker B{bcrocker}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Tolias A{atolias}{Department Physiology of Cognitive Processes}, Panzeri S{stefano} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ GleissLTLOK2012,
title = {Multisensory integration in the rat: behavioral benefits and neural correlates in parietal cortex},
year = {2012},
month = {2},
volume = {9},
pages = {196},
abstract = {The complementary information provided by our different senses greatly enhances our ability to perceive and
interact with the environment. Rodent models offer the possibility to study the underlying neural mechanisms and
computations using a range of methodologies. However, suitable behavioral tasks and cortical candidate areas
for the rodent remain to be elucidated. We developed a two-response forced-choice stimulus detection paradigm
where rats (Long Evans) were required to detect lateralized audio-visual targets presented in either uni- or multisensory configuration. After training, the animals exhibit faster reaction times and enhanced detection rates in congruent multisensory conditions and this multisensory response enhancement is strongest for weak unisensory
stimuli. These multisensory behavioral benefits mirror those described for similar tasks in humans. To localize
target areas of multisensory convergence, we performed high-resolution intrinsic imaging experiments in urethane
anaesthetized rats. We found a consistent overlap of responses to visual, somatosensory and auditory stimuli in
an elongated region which had the cytoarchitectonic properties of an association area (sparse layer IV) and which overlapped well with parietal region PtA, as defined by the Paxinos atlas. Laminar recordings confirmed the functional convergence of unisensory inputs both in current source densities and multi-unit activity. These recordings
also demonstrated multisensory response interactions and the magnitude and sign of response enhancement /
suppression was dependent on temporal stimulus order. Control experiments confirmed the specificity of the multisensory response patterns to the parietal region (in comparison to visual cortex). We developed a rodent model
of behavioral multisensory integration similar to paradigms known from human psychophysics and we show the presence of key criteria of multisensory processing in a region in the parietal cortex. Ongoing experiments directly study the neural underpinnings of behavioral benefits for enhanced stimulus detection in the behaving animal.},
web_url = {http://www.cosyne.org/c/index.php?title=Cosyne_12},
event_name = {9th Annual Computational and Systems Neuroscience Meeting (Cosyne 2012)},
event_place = {Salt Lake City, UT, USA},
state = {published},
author = {Gleiss S{sgleiss}{Research Group Physiology of Sensory Integration}, Lippert MT{mlippert}{Department Physiology of Cognitive Processes}, Takagaki K, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Ohl FW and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Conference{ DwarakanathPHE2012,
title = {Motion parallax serves as an independent cue in sound source
disambiguation},
year = {2012},
month = {11},
volume = {13},
pages = {6},
abstract = {In the absence of dominant cues to the distance of a sound source from the observer, estimating absolute or relative distance becomes difficult. Motion parallax may contribute to this estimation. However, its role as an independent cue has not yet been investigated. To address this issue, we designed an experiment that included logarithmically varying distance of sound source along the depth plane of the observer, elimination of distance related loudness
using perceptual loudness equalization and to and fro (laterally) movement of subjects while the sounds were generated in three conditions a simultaneous playback, sequential playback and simultaneous playback of phase-interrupted sounds. Sequential presentation of the low
and high sound subjects showed a substantial improvement in distance estimates relative to the baseline static condition. Improvement was also observed for the simultaneous phase interrupted sound condition. Here we demonstrate for the first time the existence of auditory
motion parallax from lateral self- motion and show that it aids distance estimation of sound position. Interestingly, a bias to perceive low frequency sounds as farther away was also observed. Auditory depth perception is improved by lateral observer motion, which alters the inter-aural difference cues available.},
web_url = {http://www.neuroschool-tuebingen-nena.de/},
event_name = {13th Conference of the Junior Neuroscientists of Tübingen (NeNA 2012)},
event_place = {Schramberg, Germany},
state = {published},
author = {Dwarakanath A{adwarakanath}{Research Group Physiology of Sensory Integration}, Parise C{cesare}{Research Group Multisensory Perception and Action}, Hartcher-O'Brien J{jhartcher}{Research Group Multisensory Perception and Action} and Ernst M{marc}{Research Group Multisensory Perception and Action}}
}

@Conference{ PanagiotaropoulosBL2012,
title = {Beta oscillations propagate as traveling waves in the macaque prefrontal cortex},
year = {2012},
month = {10},
volume = {42},
number = {413.03},
abstract = {Despite significant progress in understanding functional parcellation of the primate prefrontal cortex (PFC) it is currently unknown whether an intrinsic mechanism could dynamically coordinate activity between these functionally specialized sub-regions. Such a mechanism could be reflected in spatially organized rhythmic activity that is macroscopically observed as complex, rhythmic spatio-temporal patterns. Here, we used multielectrode arrays (Utah arrays) and recorded neural activity from a large area (16mm2) of the macaque lateral PFC during anesthesia in order to explore spatio-temporal patterns in the default state of the prefrontal cortical network. We recorded local field potentials (LFP's) (1-200Hz) and found that the spatial coherence of oscillatory activity exhibited a distinctive peak in the "beta" (15-30 Hz) frequency range during resting state but also during visual stimulation with dynamic movie stimuli. We then used the Hilbert transform to obtain the analytic signal and evaluated the two-dimensional instantaneous phase maps. We observed consistent phase gradients in the "beta" frequency range that formed complex, dynamic patterns, suggesting propagation of oscillatory activity across the cortical surface. A graph cut algorithm based on a measure of phase shift invariant similarity was used to cluster these spatio-temporal patterns. Our analysis revealed a dominant travelling wave pattern in the "beta" band, propagating along the ventral-dorsal plane and replaced by less frequent, less dominant patterns both in the absence of visual stimulation (spontaneous activity) and during stimulation with movie clips. By estimating mutual information, we found that the amplitude of this wave conveyed sensory information during the presentation of several movies. Our data show that travelling wave phenomena are suggestive of highly coordinated activity in the PFC, a cortical area known to be involved in higher order sensory processing. These traveling waves of oscillatory neural activity are modulated by sensory input and could provide a functional substrate for coordinating activity across different subregions of the PFC. Finally, our approach enables the unsupervised analysis of the complex spatio-temporal neural dynamics in ongoing oscillatory signals, providing an analytical framework to understand cooperative mechanisms in spatially distributed neural populations.},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Besserve M{besserve}{Department Empirical Inference}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ Logothetis2012_2,
title = {Large-Scale Brain Networks: Principles and Emerging Methodologies},
year = {2012},
month = {10},
volume = {42},
number = {611},
abstract = {The brain is characterized by ultra-high structural complexity and massive connectivity, both of which change and evolve in response to experience. Information is processed in both a parallel and a hierarchical fashion, and connectivity is bidirectional and continuously modulated. One major problem in studying such systems is adequately defining elementary operational units, because such modules can be complex systems in their own right. In addition, the synergistic organization of complex systems means that their behavior cannot be reduced to, or predicted from, their components.
Traditionally, topographic connectivity between different brain areas has been studied using degeneration methods and anterograde and retrograde tracer techniques. Although such studies have yielded valuable information, they require fixed, processed tissue for data analysis and say nothing about dynamic or effective connectivity.
To localize and comprehend the neural mechanisms underlying cognition, we must combine multimodal methodologies to concurrently study both large-scale networks and their components. One possibility is to combine global imaging technologies such as functional magnetic resonance imaging (fMRI) with invasive measurements of the brain’s electrical activity at the microcircuit level.
Now, novel MR-visible tracers can be infused into a specific brain region and are transported anterogradely transsynaptically, allowing us to study anatomical connectivity in vivo. Simultaneous direct electrical stimulation (DES) and fMRI (DES-fMRI) let us visualize the networks underlying electrostimulation-induced behaviors, map neuromodulatory systems, and study the effects of regional synaptic plasticity on cortical connectivity. Our own recently developed and optimized “neural event triggered functional MRI” (NET-fMRI) uses multiple-contact electrodes and fMRI to map activations induced by neural events.
This lecture will address some central questions in this research. Can we identify networks and study “relationships” between their nodes? Can we make activity maps of such networks that are robustly related to behavior? Ultimately, can we really study emerging properties, such as perception and memory, by tracking the behavior of such small- and large-scale assemblies?},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ OmerL2012,
title = {Spiral waves dynamics in primary visual cortex of the anesthetized primate},
year = {2012},
month = {10},
volume = {42},
number = {413.02},
abstract = {Spontaneous spiral cortical waves have been reported to exist in rodents under specific pharmacological manipulations as well as during induced sleep-like states (Huang et al.,2010). The role of this highly organized mesoscopic phenomenon as well as the underlying mechanism are currently elusive. Neither the emergence of these patterns nor the relationship of the spatio-temporal dynamics of the waves to the underlying cortical functional architecture are understood or even examined in detail.
Here, we used voltage sensitive dye imaging to record the dynamics of ongoing sub-threshold potentials in the anesthetized primate. Spatial phase maps at each point in time revealed, also in these experiments, the existence of spontaneously emerging spiral waves. We found that spiral waves emerged from cortical space-time dependent activity within the Theta frequency band (4-8Hz). In particular, phase singularities emerged in oscillating bursts blow 1Hz, which fits the well-known slow waves, that is, the thalamus-driven up- and down-state alternations. The spatio-temporal dynamics of the spiral waves, as well as the phase singularities were found to be constrained by the underlining functional architecture of the primate primary visual cortex. These results suggest that spiral waves are an important cortical phenomenon, in the sense that, they can shed light on some basic principles underlying cortical microcircuit dynamics at the mesoscopic level.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?mID=2964&sKey=8ff77860-91b7-47e0-a97d-694a5dca70cc&cKey=558d727d-8287-40a4-a230-bd963d1c09a8&mKey=%7B70007181-01C9-4DE9-A0A2-EEBFA14CD9F1%7D},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Omer DB{domer}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ LeeKPSL2012,
title = {Visualization of the population receptive field structures in human visual cortex},
year = {2012},
month = {10},
volume = {42},
number = {723.08},
abstract = {Functional resonance imaging (fMRI) has been used to measure the retinotopic structures of the human visual cortex in vivo. Recently, this stream of research has been advanced by introduction of a computational model to fit a predefined population receptive field (pRF) model to fMRI signals observed. This method has advantages over the previous methods by providing receptive field (RF) size as well as more accurate retinopic maps. However, this model is limited because this method need assume the pRF as a certain model (e.g., circular Gaussian).
To overcome this limitation, in the present study, we introduce a new method to visualize the pRF structure prior to modeling. This method estimates the pRF structure by fitting a set of weights representing the pRF topography in space to observed fMRI signals.
For that, let vector p and s represent a pRF topography and a stimulus aperture. When visual stimuli present through the aperture, the pRF response is given as r = ps. As the pRF response is observed in the form of fMRI signal, it is required to convolve it with a canonical hemodynamic response function h. Therefore, the final pRF prediction x is given:
x = h*r = h*(ps)
Here, * denotes convolution. From this model, vector p is estimated by using the ridge regression. Application of our method yielded clear pRF structures which include the pRF center and surround regions. In addition, some pRF centers looked elliptic while the previous method assumed the pRF is isotropic.Therefore, this approach allows scientists to select a more appropriate pRF model based on the pRF topography observed.
This application resulted in more accurate eccentricity map than the one by the previous method (directly-fitting circular Gaussian model). Furthermore, we could observe pRF properties such as elongation and orientation of the pRF center, and the surround suppression.},
web_url = {http://www.sfn.org/am2012/},
event_name = {42nd Annual Meeting of the Society for Neuroscience (Neuroscience 2012)},
event_place = {New Orleans, LA, USA},
state = {published},
author = {Lee S{slee}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Papanikolaou A{amalia}{Department Physiology of Cognitive Processes}, Smirnakis SM and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ Kerr2012,
title = {Imaging activity in neuronal populations in the freely moving animal},
year = {2012},
month = {7},
day = {16},
web_url = {http://www.bacofun.medizin.uni-mainz.de/172.php},
event_name = {BaCoFun at the 8th Forum of European Neuroscience (FENS 2012)},
event_place = {Barcelona, Spain},
state = {published},
author = {Kerr J{jkerr}{Research Group Neural Population Imaging}}
}

@Conference{ Perrodin2012_2,
title = {Neuronal representation of communication signals in the primate voice area},
year = {2012},
month = {5},
day = {24},
abstract = {Communication with other members of one's species is not restricted to human language: most primates use vocal and facial signals for social interactions and survival. Recent fMRI studies have identified brain areas dedicated to processing species-specific vocal signals ('voice' areas) in the anterior temporal lobe of both humans and nonhuman primates, and researchers have started to establish homologies between how the brains of primates process communication signals.
Nevertheless, it remains unclear how voices are represented at the neuronal level. My research uses fMRI-guided electrophysiology targeting the anterior 'voice' area to investigate the encoding of vocal features at the resolution of single neurons.
I will first describe a project in which we identified voice-sensitive cells as neurophysiological substrates associated with voice processing, and discuss how their stimulus-encoding properties relate to the putatively analogous 'face cells' in the visual system. I will then talk about more recent work quantifying and characterizing visual influences of face information on voice-sensitive neurons in the context of audiovisual communication.
This type of approach builds on the links between how the monkey and human brain process voice content, and contributes to the development of an animal model system to study the neuronal representation of auditory and visual aspects of communication signals at the neuronal level.},
file_url = {fileadmin/user_upload/files/publications/2012/Perrodin-May-2012-Poster.pdf},
web_url = {http://www.cbs.mpg.de/events/calendar/00672-1},
event_name = {Max Planck Institute for Human Cognitive and Brain Sciences},
event_place = {Leipzig, Germany},
state = {published},
author = {Perrodin C{cperrodin}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Conference{ Perrodin2012,
title = {Neuronal representation of communication signals in the primate voice area},
year = {2012},
month = {2},
day = {23},
event_name = {Affective Neuropsychiatry, Department of General Psychiatry, University of Tübingen},
event_place = {Tübingen, Germany},
state = {published},
author = {Perrodin C{cperrodin}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Book{ HospSB2011,
title = {Tentakel des Geistes: Begegnungen mit Valentin Braitenberg},
year = {2011},
pages = {324},
abstract = {Valentin Braitenbergs „Künstliche Wesen" – mit Sensoren ausgestattete Fahrzeuge, welche autark auf Umweltreize reagieren – bilden das Referenzwerk für alle, die sich mit künstlicher Intelligenz beschäftigen. Braitenberg, 1926 in Südtirol geboren, war von 1968 bis zur Emeritierung 1994 Direktor am Max-Planck-Institut für biologische Kybernetik in Tübingen und von 1998 bis 2001 Präsident des Laboratorio di Scienze Cognitive der Universität Trient in Rovereto: ein Menschen- und Forscherleben zwischen Bozen, Meran, Neapel und Tübingen, weltweit ausgreifend.
In diesem Buch erzählen Kollegen, Freunde, Familienmitglieder von ihren Begegnungen mit dem Hirnforscher und Kybernetiker, davon, wie Forschung angestoßen und zur weit übers eigene Fach hinausgehenden Denkbewegung wird, wenn „einer der großen Intellektuellen unserer Zeit“ (Niels Birbaumer) mit Wissenschaft umgeht.},
web_url = {http://www.raetia.com/index.php?id=1632},
publisher = {Edition Raetia},
address = {Bolzano, Italy},
state = {published},
ISBN = {978-88-7283-403-9},
author = {Hosp I, Sch\"uz A{schuez}{Department Physiology of Cognitive Processes} and Braitenberg Z}
}

@Article{ MurayamaAL2011,
title = {Activation of SC during electrical stimulation of LGN: retinal antidromic stimulation or corticocollicular activation?},
journal = {Magnetic Resonance Imaging},
year = {2011},
month = {12},
volume = {29},
number = {10},
pages = {1351-1357},
abstract = {We have recently used combined electrostimulation, neurophysiology, microinjection and functional magnetic resonance imaging (fMRI) to study the cortical activity patterns elicited during stimulation of cortical afferents in monkeys. We found that stimulation of a site in lateral geniculate nucleus (LGN) increases the fMRI signal in the regions of primary visual cortex receiving input from that site, but suppresses it in the retinotopically matched regions of extrastriate cortex. Intracortical injection experiments showed that such suppression is due to synaptic inhibition. During these experiments, we have consistently observed activation of superior colliculus (SC) following LGN stimulation. Since LGN does not directly project to SC, the current study investigated the origin of SC activation. By examining experimental manipulations inactivating the primary visual cortex, we present here evidence that the robust SC activation, which follows the stimulation of LGN, is due to the activation of corticocollicular pathway.},
web_url = {http://www.sciencedirect.com/science?_ob=MiamiImageURL&_cid=271222&_user=29041&_pii=S0730725X11002815&_check=y&_origin=&_coverDate=31-Dec-2011&view=c&wchp=dGLbVlk-zSkWb&md5=3345ba26e8571bce55f0cf39b413ca17/1-s2.0-S0730725X11002815-main.pdf},
state = {published},
DOI = {10.1016/j.mri.2011.08.002},
author = {Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Augath M{mark}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ SultanAMTL2011,
title = {esfMRI of the upper STS: further evidence for the lack of electrically induced polysynaptic propagation of activity in the neocortex},
journal = {Magnetic Resonance Imaging},
year = {2011},
month = {12},
volume = {29},
number = {10},
pages = {1374-1381},
abstract = {Combining electrical stimulation with fMRI (esfMRI) has proven to be an important tool to study the global effects of electrical stimulation on neural networks in the brain. Here we extend our previous studies to stimulating the upper superior temporal sulcus (STS) in the anesthetized monkey. Our results show that stimulating area V5/MT and surrounding areas leads to positive BOLD responses in the majority of cortical areas known to receive direct/monosynaptic connections from the stimulation site. We confirm our previous results from stimulating primary visual cortex that the propagation of electrically induced activity is limited in its transsynaptic propagation to the first synapse also for extrastriate areas.},
web_url = {http://www.sciencedirect.com/science?_ob=MiamiImageURL&_cid=271222&_user=29041&_pii=S0730725X11001354&_check=y&_origin=&_coverDate=31-Dec-2011&view=c&wchp=dGLzVBA-zSkWz&md5=1ebff3056d9b781fb0d326346e0f58f1/1-s2.0-S0730725X11001354-main.pdf},
state = {published},
DOI = {10.1016/j.mri.2011.04.005},
author = {Sultan F, Augath M{mark}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Tolias AS{atolias}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ MagriLP2011,
title = {Investigating static nonlinearities in neurovascular coupling},
journal = {Magnetic Resonance Imaging},
year = {2011},
month = {12},
volume = {29},
number = {10},
pages = {1358-1364},
abstract = {Many statistical models of coupling between time changes of the band-limited power of neural signals and functional magnetic resonance imaging Blood Oxygenation Level Dependent (BOLD) signal time changes rely on linear convolution. The effect of nonlinear behaviors in single-trial relationships between neural signals and BOLD responses is rarely tested and included in models. Here we investigate whether using a static nonlinearity improves the prediction of single-trial BOLD responses from neural signals. A static nonlinearity is a nonlinear transformation of the convolution of neural responses which is implemented by the same nonlinear function for all time points. We evaluated this approach by applying it to simultaneous recordings of functional magnetic resonance imaging BOLD and band-limited neural signals (Local Field Potentials and Multi Unit Activity) from primary visual cortex of anaesthetized macaques. We found that using a simple polynomial static nonlinearity was sufficient to obtain highly significant improvements of the accuracy of single-trial BOLD prediction over the accuracy obtained with linear convolution. This suggests that static nonlinearities may be a useful tool for a compact and accurate statistical description of neurovascular coupling.},
web_url = {http://www.sciencedirect.com/science?_ob=MiamiImageURL&_cid=271222&_user=29041&_pii=S0730725X11001470&_check=y&_origin=&_coverDate=31-Dec-2011&view=c&wchp=dGLbVlt-zSkWz&md5=2868266f9c3424b818a3e64166634a31/1-s2.0-S0730725X11001470-main.pdf},
state = {published},
DOI = {10.1016/j.mri.2011.04.017},
author = {Magri C{cmagri}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Article{ StoewerGKBLDS2011_2,
title = {Realignment strategies for awake-monkey fMRI data},
journal = {Magnetic Resonance Imaging},
year = {2011},
month = {12},
volume = {29},
number = {10},
pages = {1390-1400},
abstract = {Functional magnetic resonance imaging (fMRI) experiments with awake nonhuman primates (NHPs) have recently seen a surge of applications. However, the standard fMRI analysis tools designed for human experiments are not optimal for NHP data collected at high fields. One major difference is the experimental setup. Although real head movement is impossible for NHPs, MRI image series often contain visible motion artifacts. Animal body movement results in image position changes and geometric distortions. Since conventional realignment methods are not appropriate to address such differences, algorithms tailored specifically for animal scanning become essential. We have implemented a series of high-field NHP specific methods in a software toolbox, fMRI Sandbox (http://kyb.tuebingen.mpg.de/~stoewer/), which allows us to use different realignment strategies. Here we demonstrate the effect of different realignment strategies on the analysis of awake-monkey fMRI data acquired at high field (7 T). We show that the advantage of using a nonstandard realignment algorithm depends on the amount of distortion in the dataset. While the benefits for less distorted datasets are minor, the improvement of statistical maps for heavily distorted datasets is significant.},
web_url = {http://www.sciencedirect.com/science?_ob=MiamiImageURL&_cid=271222&_user=29041&_pii=S0730725X11001809&_check=y&_origin=&_coverDate=31-Dec-2011&view=c&wchp=dGLzVBA-zSkWb&md5=faaec51a67a063db4ac8f1979129b81b/1-s2.0-S0730725X11001809-main.pdf},
state = {published},
DOI = {10.1016/j.mri.2011.05.003},
author = {Stoewer S{stoewer}{Department Physiology of Cognitive Processes}, Goense J{jozien}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Bartels A{abartels}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Duncan J and Sigala N{natasha}{Department Physiology of Cognitive Processes}}
}

@Article{ BartlettOLH2011,
title = {Saccades during Object Viewing Modulate Oscillatory Phase in the Superior Temporal Sulcus},
journal = {Journal of Neuroscience},
year = {2011},
month = {12},
volume = {31},
number = {5},
pages = {18423-18432},
abstract = {Saccadic eye movements (SEMs) are the primary means of gating visual information in primates and strongly influence visual perception. The active exploration of the visual environment (“active vision”) via SEMs produces suppression during saccades and enhancement afterward (i.e., during fixation) in occipital visual areas. In lateral temporal lobe visual areas, the influence, if any, of eye movements is less well understood, despite the necessity of these areas for forming coherent percepts of objects. The upper bank of the superior temporal sulcus (uSTS) is one such area whose sensitivity to SEMs is unknown. We therefore examined how saccades modulate local field potentials (LFPs) in the uSTS of macaque monkeys while they viewed face and nonface object stimuli. LFP phase concentration increased following fixation onset in the alpha (8–14 Hz), beta (14–30 Hz), and gamma (30–60 Hz) bands and was distinct from the image-evoked response. Furthermore, near-coincident onsets of fixation and image presentation—like those occurring in active vision—led to enhanced responses through greater phase concentration in the same frequency bands. Finally, single-unit activity was modulated by the phase of alpha, beta, and gamma oscillations, suggesting that the observed phase-locking influences spike timing in uSTS. Previous research implicates phase concentration in these frequency bands as a correlate of perceptual performance (Womelsdorf et al., 2006; Bosman et al., 2009). Together, these results demonstrate sensitivity to eye movements in an object-processing region of the brain and represent a plausible neural basis for the enhancement of object processing during active vision.},
web_url = {http://www.jneurosci.org/content/31/50/18423.full.pdf+html},
state = {published},
DOI = {10.1523/​JNEUROSCI.4102-11.2011},
author = {Bartlett AM, Ovaysikia S, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Hoffman KL{kari}{Department Physiology of Cognitive Processes}}
}

@Article{ WatanabeCMUATL2011,
title = {Attention But Not Awareness Modulates the BOLD Signal in the Human V1 During Binocular Suppression},
journal = {Science},
year = {2011},
month = {11},
volume = {334},
number = {6057},
pages = {829-831},
abstract = {Although recent psychophysical studies indicate that visual awareness and top-down attention are two distinct processes, it is not clear how they are neurally dissociated in the visual system. Using a two-by-two factorial functional magnetic resonance imaging design with binocular suppression, we found that the visibility or invisibility of a visual target led to only nonsignificant blood oxygenation level–dependent (BOLD) effects in the human primary visual cortex (V1). Directing attention toward and away from the target had much larger and robust effects across all study participants. The difference in the lower-level limit of BOLD activation between attention and awareness illustrates dissociated neural correlates of the two processes. Our results agree with previously reported V1 BOLD effects on attention, while they invite a reconsideration of the functional role of V1 in visual awareness.},
web_url = {http://www.sciencemag.org/content/334/6057/829.full.pdf},
state = {published},
DOI = {10.1126/science.1203161},
author = {Watanabe M{watanabe}{Department Physiology of Cognitive Processes}, Cheng K, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Ueno K, Asamizuya T, Tanaka K and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ AggelopoulosLLR2011,
title = {Cholinergic control of visual categorization in macaques},
journal = {Frontiers in Behavioral Neuroscience},
year = {2011},
month = {11},
volume = {5},
number = {73},
pages = {1-10},
abstract = {Acetylcholine (ACh) is a neurotransmitter acting via muscarinic and nicotinic receptors that is implicated in several cognitive functions and impairments, such as Alzheimer’s disease. It is believed to especially affect the acquisition of new information, which is particularly important when behavior needs to be adapted to new situations and to novel sensory events. Categorization, the process of assigning stimuli to a category, is a cognitive function that also involves information acquisition. The role of ACh on categorization has not been previously studied. We have examined the effects of scopolamine, an antagonist of muscarinic ACh receptors, on visual categorization in macaque monkeys using familiar and novel stimuli. When the peripheral effects of scopolamine on the parasympathetic nervous system were controlled for, categorization performance was disrupted following systemic injections of scopolamine. This impairment was observed only when the stimuli that needed to be categorized had not been seen before. In other words, the monkeys were not impaired by the central action of scopolamine in categorizing a set of familiar stimuli (stimuli which they had categorized successfully in previous sessions). Categorization performance also deteriorated as the stimulus became less salient by an increase in the level of visual noise. However, scopolamine did not cause additional performance disruptions for difficult categorization judgments at lower coherence levels. Scopolamine, therefore, specifically affects the assignment of new exemplars to established cognitive categories, presumably by impairing the processing of novel information. Since we did not find an effect of scopolamine in the categorization of familiar stimuli, scopolamine had no significant central action on other cognitive functions such as perception, attention, memory, or executive control within the context of our categorization task.},
web_url = {http://www.frontiersin.org/Journal/DownloadFile.ashx?pdf=1&FileId=%2023441&articleId=%2015225&Version=%201&ContentTypeId=21&FileName=%20fnbeh-05-00073.pdf},
state = {published},
DOI = {10.3389/fnbeh.2011.00073},
author = {Aggelopoulos NC{aggelopoulos}{Department Physiology of Cognitive Processes}, Liebe S{sliebe}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Article{ TheodoniPKLD2011,
title = {Cortical microcircuit dynamics mediating binocular rivalry: the role of adaptation in inhibition},
journal = {Frontiers in Human Neuroscience},
year = {2011},
month = {11},
volume = {5},
number = {145},
pages = {1-19},
abstract = {Perceptual bistability arises when two conflicting interpretations of an ambiguous stimulus or images in binocular rivalry (BR) compete for perceptual dominance. From a computational point of view, competition models based on cross-inhibition and adaptation have shown that noise is a crucial force for rivalry, and operates in balance with adaptation. In particular, noise-driven transitions and adaptation-driven oscillations define two dynamical regimes and the system explains the observed alternations in perception when it operates near their boundary. In order to gain insights into the microcircuit dynamics mediating spontaneous perceptual alternations, we used a reduced recurrent attractor-based biophysically realistic spiking network, well known for working memory, attention, and decision making, where a spike-frequency adaptation mechanism is implemented to account for perceptual bistability. We thus derived a consistently reduced four-variable population rate model using mean-field techniques, and we tested it on BR data collected from human subjects. Our model accounts for experimental data parameters such as mean time dominance, coefficient of variation, and gamma distribution fit. In addition, we show that our model operates near the bifurcation that separates the noise-driven transitions regime from the adaptation-driven oscillations regime, and agrees with Levelt’s second revised and fourth propositions. These results demonstrate for the first time that a consistent reduction of a biophysically realistic spiking network of leaky integrate-and-fire neurons with spike-frequency adaptation could account for BR. Moreover, we demonstrate that BR can be explained only through the dynamics of competing neuronal pools, without taking into account the adaptation of inhibitory interneurons. However, the adaptation of interneurons affects the optimal parametric space of the system by decreasing the overall adaptation necessary for the bifurcation to occur, and introduces oscillations in the spontaneous state.},
web_url = {http://www.frontiersin.org/Journal/DownloadFile.ashx?pdf=1&FileId=%2052745&articleId=%2014281&Version=%201&ContentTypeId=21&FileName=%20fnhum-05-00145.pdf},
state = {published},
DOI = {10.3389/fnhum.2011.00145},
author = {Theodoni P, Panagiotaropoulos TI{theofanis}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Deco G}
}

@Article{ SzymanskiRMPS2011,
title = {The Laminar and Temporal Structure of Stimulus Information in the Phase of Field Potentials of Auditory Cortex},
journal = {Journal of Neuroscience},
year = {2011},
month = {11},
volume = {31},
number = {44},
pages = {15787-15801},
abstract = {Recent studies have shown that the phase of low-frequency local field potentials (LFPs) in sensory cortices carries a significant amount of information about complex naturalistic stimuli, yet the laminar circuit mechanisms and the aspects of stimulus dynamics responsible for generating this phase information remain essentially unknown. Here we investigated these issues by means of an information theoretic analysis of LFPs and current source densities (CSDs) recorded with laminar multi-electrode arrays in the primary auditory area of anesthetized rats during complex acoustic stimulation (music and broadband 1/f stimuli). We found that most LFP phase information originated from discrete “CSD events” consisting of granular–superficial layer dipoles of short duration and large amplitude, which we hypothesize to be triggered by transient thalamocortical activation. These CSD events occurred at rates of 2–4 Hz during both stimulation with complex sounds and silence. During stimulation with complex sounds, these events reliably reset the LFP phases at specific times during the stimulation history. These facts suggest that the informativeness of LFP phase in rat auditory cortex is the result of transient, large-amplitude events, of the “evoked” or “driving” type, reflecting strong depolarization in thalamo-recipient layers of cortex. Finally, the CSD events were characterized by a small number of discrete types of infragranular activation. The extent to which infragranular regions were activated was stimulus dependent. These patterns of infragranular activations may reflect a categorical evaluation of stimulus episodes by the local circuit to determine whether to pass on stimulus information through the output layers.},
web_url = {http://www.jneurosci.org/content/31/44/15787.full.pdf+html},
state = {published},
DOI = {10.1523/​JNEUROSCI.1416-11.2011},
author = {Szymanski FD, Rabinowitz NC, Magri C{cmagri}{Department Physiology of Cognitive Processes}, Panzeri S{stefano} and Schnupp JWH}
}

@Article{ Schuz2011,
title = {Valentin Braitenberg: Nachruf},
journal = {Nervenheilkunde},
year = {2011},
month = {11},
volume = {2011},
number = {11},
pages = {930-931},
file_url = {fileadmin/user_upload/files/publications/2011/Nachruf_Nervenheilkunde.pdf},
state = {published},
author = {Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}}
}

@Article{ MishraSEBLC2011,
title = {Biocytin-derived MRI contrast agent for longitudinal brain connectivity studies},
journal = {ACS Chemical Neuroscience},
year = {2011},
month = {10},
volume = {2},
number = {10},
pages = {578–587},
abstract = {To investigate the connectivity of brain networks noninvasively and dynamically, we have developed a new strategy to functionalize neuronal tracers and designed a biocompatible probe that can be visualized in vivo using magnetic resonance imaging (MRI). Furthermore, the multimodal design used allows combined ex vivo studies with microscopic spatial resolution by conventional histochemical techniques. We present data on the functionalization of biocytin, a well-known neuronal tract tracer, and demonstrate the validity of the approach by showing brain networks of cortical connectivity in live rats under MRI, together with the corresponding microscopic details, such as fibers and neuronal morphology under light microscopy. We further demonstrate that the developed molecule is the first MRI-visible probe to preferentially trace retrograde connections. Our study offers a new platform for the development of multimodal molecular imaging tools of broad interest in neuroscience, that capture in vivo the dynamics of large scale neural networks together with their microscopic characteristics, thereby spanning several organizational levels.},
web_url = {http://pubs.acs.org/doi/pdf/10.1021/cn200022m},
state = {published},
DOI = {10.1021/cn200022m},
author = {Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}, Engelmann J{joern}{Department High-Field Magnetic Resonance}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Canals S{canals}}
}

@Article{ DahlLBW2011,
title = {Second-Order Relational Manipulations Affect Both Humans and Monkeys},
journal = {PLoS One},
year = {2011},
month = {10},
volume = {6},
number = {10},
pages = {1-7},
abstract = {Recognition and individuation of conspecifics by their face is essential for primate social cognition. This ability is driven by a mechanism that integrates the appearance of facial features with subtle variations in their configuration (i.e., second-order relational properties) into a holistic representation. So far, there is little evidence of whether our evolutionary ancestors show sensitivity to featural spatial relations and hence holistic processing of faces as shown in humans. Here, we directly compared macaques with humans in their sensitivity to configurally altered faces in upright and inverted orientations using a habituation paradigm and eye tracking technologies. In addition, we tested for differences in processing of conspecific faces (human faces for humans, macaque faces for macaques) and non-conspecific faces, addressing aspects of perceptual expertise. In both species, we found sensitivity to second-order relational properties for conspecific (expert) faces, when presented in upright, not in inverted, orientation. This shows that macaques possess the requirements for holistic processing, and thus show similar face processing to that of humans.},
web_url = {http://www.plosone.org/article/fetchObjectAttachment.action;jsessionid=479810543A9D0DDB1F0DBC45F84CA66C.ambra02?uri=info%3Adoi%2F10.1371%2Fjournal.pone.0025793&representation=PDF},
state = {published},
DOI = {10.1371/journal.pone.0025793},
EPUB = {e25793},
author = {Dahl CD{dahl}{Department Human Perception, Cognition and Action}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, B\"ulthoff HH{hhb}{Department Human Perception, Cognition and Action} and Wallraven C{walli}{Department Human Perception, Cognition and Action}}
}

@Article{ EckerBTB2011,
title = {The effect of noise correlations in populations of diversely tuned neurons},
journal = {Journal of Neuroscience},
year = {2011},
month = {10},
volume = {31},
number = {40},
pages = {14272-14283},
abstract = {The amount of information encoded by networks of neurons critically depends on the correlation structure of their activity. Neurons with similar stimulus preferences tend to have higher noise correlations than others. In homogeneous populations of neurons, this limited range correlation structure is highly detrimental to the accuracy of a population code. Therefore, reduced spike count correlations under attention, after adaptation, or after learning have been interpreted as evidence for a more efficient population code. Here, we analyze the role of limited range correlations in more realistic, heterogeneous population models. We use Fisher information and maximum-likelihood decoding to show that reduced correlations do not necessarily improve encoding accuracy. In fact, in populations with more than a few hundred neurons, increasing the level of limited range correlations can substantially improve encoding accuracy. We found that this improvement results from a decrease in noise entropy that is associated with increasing correlations if the marginal distributions are unchanged. Surprisingly, for constant noise entropy and in the limit of large populations, the encoding accuracy is independent of both structure and magnitude of noise correlations.},
web_url = {http://www.jneurosci.org/content/31/40/14272.full.pdf+html},
state = {published},
DOI = {10.1523/​JNEUROSCI.2539-11.2011},
author = {Ecker AS{aecker}{Research Group Computational Vision and Neuroscience}, Berens P{berens}{Research Group Computational Vision and Neuroscience}, Tolias AS{atolias}{Department Physiology of Cognitive Processes} and Bethge M{mbethge}{Research Group Computational Vision and Neuroscience}}
}

@Article{ PlacidiENLA2011,
title = {An aryl-phosphonate appended macrocyclic platform for lanthanide based bimodal imaging agents},
journal = {Chemical Communications},
year = {2011},
month = {9},
volume = {47},
number = {41},
pages = {11534-11536},
abstract = {Four ligand systems have been prepared whose characteristics are well suited to the design of bimodal MRI and luminescence probes. The lanthanide complexes display high relaxivities and luminescence quantum yields. These properties are retained at higher magnetic fields and in a range of competitive environments including model extracellular medium and cultured cells.},
web_url = {http://pubs.rsc.org/en/content/articlepdf/2011/cc/c1cc14437e},
state = {published},
DOI = {10.1039/C1CC14437E},
author = {Placidi MP{matteo}{Department Physiology of Cognitive Processes}, Engelmann J{joern}{Department High-Field Magnetic Resonance}, Natrajan LS, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Angelovski G{goran}{Department Physiology of Cognitive Processes}}
}

@Article{ ValverdeSalzmannWLS2011,
title = {Multimodal vessel mapping for precise large area alignment of functional optical imaging data to neuroanatomical preparations in marmosets},
journal = {Journal of Neuroscience Methods},
year = {2011},
month = {9},
volume = {201},
number = {1},
pages = {159-172},
abstract = {Imaging technologies, such as intrinsic optical imaging (IOI), functional magnetic resonance imaging (fMRI) or multiphoton microscopy provide excellent opportunities to study the relationship between functional signals recorded from a cortical area and the underlying anatomical structure. This, in turn, requires accurate alignment of the recorded functional imaging data with histological datasets from the imaged tissue obtained after the functional experiment. This alignment is complicated by distortions of the tissue which naturally occur during histological treatment, and is particularly difficult to achieve over large cortical areas, such as primate visual areas. We present here a method that uses IOI vessel maps revealed in the time course of the intrinsic signal, in combination with vascular casts and vascular lumen labeling techniques together with a pseudo three dimensional (p3D) reconstruction of the tissue architecture in order to facilitate alignment of IOI data with posthoc histological datasets. We demonstrate that by such a multimodal vessel mapping approach, we are able to constitute a hook in anatomical-functional data alignment that enables the accurate assignment of functional signals over large cortical regions. As an example, we present precise alignments of IOI responses showing orientation selectivity of primate V1 with anatomical sections stained for cytochrome-oxidase-reactivity.},
web_url = {http://www.sciencedirect.com/science?_ob=MiamiImageURL&_cid=271055&_user=29041&_pii=S0165027011004584&_check=y&_origin=&_coverDate=30-Sep-2011&view=c&wchp=dGLzVlB-zSkWz&md5=02ccc2eea51f6889a3cd0629dfffe55a/1-s2.0-S0165027011004584-main.pdf},
state = {published},
DOI = {10.1016/j.jneumeth.2011.07.029},
author = {Valverde Salzmann MF{valverde}, Wallace DJ{dhw}{Research Group Neural Population Imaging}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}}
}

@Article{ 5283,
title = {Rivalry between afterimages and real images: the influence of the percept and the eye},
journal = {Journal of Vision},
year = {2011},
month = {8},
volume = {11},
number = {9:7},
pages = {1-13},
abstract = {In binocular rivalry, the conscious percept alternates stochastically between two images shown to the two eyes. Both suppressed and dominant images form afterimages (AIs) whose strength depends on the perceptual state during induction. Counterintuitively, when these two AIs rival, the AI of the previously suppressed percept gains initial dominance, even when it is weaker. Here, we examined rivalry between afterimages, between real images, and between both to examine eye-based and binocular contributions to this effect. In all experiments, we found that for both AIs and real images, the suppressed percept consistently gained initial dominance following a long suppression period. Dominance reversals failed to occur following short suppression periods and depended on an abrupt change (removal) of the stimulus. With real images, results were replicated also when eye channels were exchanged during the abrupt change. The initial dominance of the weaker, previously suppressed percept is thus not due to its weaker contrast, to it being an afterimage, or to monocular adaptation effects as previously suggested. Instead, it is due to binocular, higher level effects that favor a perceptual switch after prolonged dominance. We discuss a plausible neural account for these findings in terms of neural interactions between binocular and eye-related stages.},
web_url = {http://www.journalofvision.org/content/11/9/7.full.pdf+html},
state = {published},
DOI = {10.1167/11.9.7},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}, Vazquez-Zuniga Y, Schindler A{aschindler}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ BlaschkoSBLG2011,
title = {Semi-supervised kernel canonical correlation analysis with application to human fMRI},
journal = {Pattern Recognition Letters},
year = {2011},
month = {8},
volume = {32},
number = {11},
pages = {1572-1583},
abstract = {Kernel canonical correlation analysis (KCCA) is a general technique for subspace learning that incorporates principal components analysis (PCA) and Fisher linear discriminant analysis (LDA) as special cases. By finding directions that maximize correlation, KCCA learns representations that are more closely tied to the underlying process that generates the data and can ignore high-variance noise directions. However, for data where acquisition in one or more modalities is expensive or otherwise limited, KCCA may suffer from small sample effects. We propose to use semi-supervised Laplacian regularization to utilize data that are present in only one modality. This approach is able to find highly correlated directions that also lie along the data manifold, resulting in a more robust estimate of correlated subspaces.

Functional magnetic resonance imaging (fMRI) acquired data are naturally amenable to subspace techniques as data are well aligned. fMRI data of the human brain are a particularly interesting candidate. In this study we implemented various supervised and semi-supervised versions of KCCA on human fMRI data, with regression to single and multi-variate labels (corresponding to video content subjects viewed during the image acquisition). In each variate condition, the semi-supervised variants of KCCA performed better than the supervised variants, including a supervised variant with Laplacian regularization. We additionally analyze the weights learned by the regression in order to infer brain regions that are important to different types of visual processing.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6V15-525YP08-1-1&_cdi=5665&_user=29041&_pii=S0167865511000481&_origin=&_coverDate=08%2F01%2F2011&_sk=999679988&view=c&wchp=dGLzVlb-zSkWb&md5=3fa7f7fa69d4474fd7a5a712a7266b8c&ie=/sdarticle.pdf},
web_url2 = {http://www.robots.ox.ac.uk/~vgg/publications-new/Public/2011/Blaschko11a/blaschko11a.pdf},
state = {published},
DOI = {10.1016/j.patrec.2011.02.011},
author = {Blaschko MB{blaschko}{Department Empirical Inference}, Shelton JA{jshelton}{Department Empirical Inference}, Bartels A{abartels}{Department Physiology of Cognitive Processes}, Lampert CH{chl}{Department Empirical Inference} and Gretton A{arthur}{Department Empirical Inference}}
}

@Article{ PerrodinKLP2011,
title = {Voice Cells in the Primate Temporal Lobe},
journal = {Current Biology},
year = {2011},
month = {8},
volume = {21},
number = {16},
pages = {1408-1415},
abstract = {Communication signals are important for social interactions and survival and are thought to receive specialized processing in the visual and auditory systems. Whereas the neural processing of faces by face clusters and face cells has been repeatedly studied [1,2,3,4,5], less is known about the neural representation of voice content. Recent functional magnetic resonance imaging (fMRI) studies have localized voice-preferring regions in the primate temporal lobe [6,7], but the hemodynamic response cannot directly assess neurophysiological properties. We investigated the responses of neurons in an fMRI-identified voice cluster in awake monkeys, and here we provide the first systematic evidence for voice cells. “Voice cells” were identified, in analogy to “face cells,” as neurons responding at least 2-fold stronger to conspecific voices than to “nonvoice” sounds or heterospecific voices. Importantly, whereas face clusters are thought to contain high proportions of face cells [4] responding broadly to many faces [1,2,4,5,8,9,10], we found that voice clusters contain moderate proportions of voice cells. Furthermore, individual voice cells exhibit high stimulus selectivity. The results reveal the neurophysiological bases for fMRI-defined voice clusters in the primate brain and highlight potential differences in how the auditory and visual systems generate selective representations of communication signals.},
file_url = {fileadmin/user_upload/files/publications/2011/Perrodin_Voice_cells_CB_2011.pdf},
web_url = {http://www.sciencedirect.com/science/article/pii/S0960982211008293},
state = {published},
DOI = {10.1016/j.cub.2011.07.028},
author = {Perrodin C{cperrodin}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Petkov C{chrisp}}
}

@Article{ HenigMFTLAM2011,
title = {Influence of Calcium-Induced Aggregation on the Sensitivity of Aminobis(methylenephosphonate)-Containing Potential MRI Contrast Agents},
journal = {Inorganic Chemistry},
year = {2011},
month = {7},
volume = {50},
number = {14},
pages = {6472–6481},
abstract = {A novel class of 1,4,7,10-tetraazacyclododecane-1,4,7-tris(methylenecarboxylic) acid (DO3A)-based lanthanide complexes with relaxometric response to Ca2+ was synthesized, and their physicochemical properties were investigated. Four macrocyclic ligands containing an alkyl-aminobis(methylenephosphonate) side chain for Ca2+-chelation have been studied (alkyl is propyl, butyl, pentyl, and hexyl for L1, L2, L3, and L4, respectively). Upon addition of Ca2+, the r1 relaxivity of their Gd3+ complexes decreased up to 61% of the initial value for the best compounds GdL3 and GdL4. The relaxivity of the complexes was concentration dependent (it decreases with increasing concentration). Diffusion NMR studies on the Y3+ analogues evidenced the formation of agglomerates at higher concentrations; the aggregation becomes even more important in the presence of Ca2+. 31P NMR experiments on EuL1 and EuL4 indicated the coordination of a phosphonate to the Ln3+ for the ligand with a propyl chain, while phosphonate coordination was not observed for the analogue bearing a hexyl linker. Potentiometric titrations yielded protonation constants of the Gd3+ complexes. log KH1 values for all complexes lie between 6.12 and 7.11 whereas log KH2 values are between 4.61 and 5.87. Luminescence emission spectra recorded on the Eu3+ complexes confirmed the coordination of a phosphonate group to the Ln3+ center in EuL1. Luminescence lifetime measurements showed that Ca-induced agglomeration reduces the hydration number which is the main cause for the change in r1. Variable temperature 17O NMR experiments evidenced high water exchange rates on GdL1, GdL2, and GdL3 comparable to that of the aqua ion.},
web_url = {http://pubs.acs.org/doi/pdf/10.1021/ic1024235},
state = {published},
DOI = {10.1021/ic1024235},
author = {Henig J, Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, Fouskov{\'a} P, Toth E, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Angelovski G{goran}{Department Physiology of Cognitive Processes} and Meyer HA}
}

@Article{ MamdedovLA2011,
title = {Structure-related variable responses of calcium sensitive MRI probes},
journal = {Organic & Biomolecular Chemistry},
year = {2011},
month = {7},
volume = {9},
number = {16},
pages = {5816-5824},
abstract = {A new series of Gd3+ complexes based on DO3A (GdL1–GdL4) was synthesized and investigated. They possess side chains with different structures which determine their varying binding properties and response towards endogenous metal ions, measured by changes in the longitudinal relaxivity (r1). GdL4 exhibits the highest selectivity toward Ca2+ in comparison to the other complexes, with up to a 63% increase of the r1. GdL2 and GdL3 also respond to different Ca2+ concentration ranges, however with a lower selectivity since the r1 changes are also observed in the presence of other cations such as Mg2+, Zn2+ or Cu2+. Assessment of the hydration number (q) via luminescence lifetime measurements confirmed that the change in q is responsible for the r1 response for all the complexes.},
web_url = {http://pubs.rsc.org/en/content/articlepdf/2011/ob/c1ob05463e},
state = {published},
DOI = {10.1039/C1OB05463E},
author = {Mamdedov I{ilgar}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Angelovski G{goran}{Department Physiology of Cognitive Processes}}
}

@Article{ MazzoniBCLP2011,
title = {Cortical dynamics during naturalistic sensory stimulations: Experiments and models},
journal = {Journal of Physiology - Paris},
year = {2011},
month = {6},
volume = {105},
number = {1-3},
pages = {2–15},
abstract = {We report the results of our experimental and theoretical investigations of the neural response dynamics in primary visual cortex (V1) during naturalistic visual stimulation. We recorded Local Field Potentials (LFPs) and spiking activity from V1 of anaesthetized macaques during binocular presentation of Hollywood color movies. We analyzed these recordings with information theoretic methods, and found that visual information was encoded mainly by two bands of LFP responses: the network fluctuations measured by the phase and power of low-frequency (less than 12 Hz) LFPs; and fast gamma-range (50–100 Hz) oscillations. Both the power and phase of low frequency LFPs carried information largely complementary to that carried by spikes, whereas gamma range oscillations carried information largely redundant to that of spikes. To interpret these results within a quantitative theoretical framework, we then simulated a sparsely connected recurrent network of excitatory and inhibitory neurons receiving slowly varying naturalistic inputs, and we determined how the LFPs generated by the network encoded information about the inputs. We found that this simulated recurrent network reproduced well the experimentally observed dependency of LFP information upon frequency. This network encoded the overall strength of the input into the power of gamma-range oscillations generated by inhibitory–excitatory neural interactions, and encoded slow variations in the input by entraining the network LFP at the corresponding frequency. This dynamical behavior accounted quantitatively for the independent information carried by high and low frequency LFPs, and for the experimentally observed cross-frequency coupling between phase of slow LFPs and the power of gamma LFPs. We also present new results showing that the model’s dynamics also accounted for the extra visual information that the low-frequency LFP phase of spike firing carries beyond that carried by spike rates. Overall, our results suggest biological mechanisms by which cortex can multiplex information about naturalistic sensory environments.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0928425711000179},
state = {published},
DOI = {10.1016/j.jphysparis.2011.07.014},
author = {Mazzoni A, Brunel N, Cavallari S, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Article{ PipaM2011,
title = {Higher Order Spike Synchrony in Prefrontal Cortex during Visual Memory},
journal = {Frontiers in Computational Neuroscience},
year = {2011},
month = {6},
volume = {5},
number = {23},
pages = {1-13},
abstract = {Precise temporal synchrony of spike firing has been postulated as an important neuronal mechanism for signal integration and the induction of plasticity in neocortex. As prefrontal cortex plays an important role in organizing memory and executive functions, the convergence of multiple visual pathways onto PFC predicts that neurons should preferentially synchronize their spiking when stimulus information is processed. Furthermore, synchronous spike firing should intensify if memory processes require the induction of neuronal plasticity, even if this is only for short-term. Here we show with multiple simultaneously recorded units in ventral prefrontal cortex that neurons participate in 3 ms precise synchronous discharges distributed across multiple sites separated by at least 500 μm. The frequency of synchronous firing is modulated by behavioral performance and is specific for the memorized visual stimuli. In particular, during the memory period in which activity is not stimulus driven, larger groups of up to seven sites exhibit performance dependent modulation of their spike synchronization.},
web_url = {http://www.frontiersin.org/computational_neuroscience/10.3389/fncom.2011.00023/abstract},
state = {published},
DOI = {10.3389/fncom.2011.00023},
author = {Pipa G{gpipa} and Munk MHJ{munk}{Department Physiology of Cognitive Processes}}
}

@Article{ SigalaLR2011,
title = {Own-species bias in the representations of monkey and human face categories in the primate temporal lobe},
journal = {Journal of Neurophysiology},
year = {2011},
month = {6},
volume = {105},
number = {6},
pages = {2740-2752},
abstract = {Face categorization is fundamental for social interactions of primates and is crucial for determining conspecific groups and mate choice. Current evidence suggests that faces are processed by a set of well-defined brain areas. What is the fine structure of this representation, and how is it affected by visual experience? Here, we investigated the neural representations of human and monkey face categories using realistic three-dimensional morphed faces that spanned the continuum between the two species. We found an “own-species” bias in the categorical representation of human and monkey faces in the monkey inferior temporal cortex at the level of single neurons as well as in the population response analyzed using a pattern classifier. For monkey and human subjects, we also found consistent psychophysical evidence indicative of an own-species bias in face perception. For both behavioural and neural data, the species boundary was shifted away from the center of the morph continuum, for each species toward their own face category. This shift may reflect visual expertise for members of one's own species and be a signature of greater brain resources assigned to the processing of privileged categories. Such boundary shifts may thus serve as sensitive and robust indicators of encoding strength for categories of interest.},
web_url = {http://jn.physiology.org/content/105/6/2740.full.pdf+html},
state = {published},
DOI = {10.​1152/​jn.​00882.​2010},
author = {Sigala R{sigala}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Article{ RioHMG2011,
title = {Partial amplitude synchronization detection in brain signals using Bayesian Gaussian mixture models},
journal = {Journal of Physiology},
year = {2011},
month = {6},
volume = {105},
number = {1-3},
pages = {98-105},
abstract = {The present work investigates instantaneous synchronization in multivariate signals. It introduces a new method to detect subsets of synchronized time series that do not consider any baseline information. The method is based on a Bayesian Gaussian mixture model applied at each location of a time–frequency map. The work assesses the relevance of detected subsets by a stability measure. The application to Local Field Potentials measured during a visuo-motor experiment in monkeys reveals a subset of synchronized time series measured in the visual cortex.},
web_url = {http://www.sciencedirect.com/science?_ob=MiamiImageURL&_cid=271945&_user=29041&_pii=S0928425711000210&_check=y&_origin=&_coverDate=30-Jun-2011&view=c&wchp=dGLzVlt-zSkWb&md5=a0a93a12bc6a344bfaa430fac3471326/1-s2.0-S0928425711000210-main.pdf},
state = {published},
DOI = {10.1016/j.jphysparis.2011.07.018},
author = {Rio M, Hutt A, Munk M{munk}{Department Physiology of Cognitive Processes} and Girau B}
}

@Article{ AngelovskiM2011,
title = {Cation-Responsive MRI Contrast Agents Based on Gadolinium(III)},
journal = {Current Inorganic Chemistry},
year = {2011},
month = {5},
volume = {1},
number = {1},
pages = {76-90},
abstract = {Magnetic resonance imaging (MRI) offers the ability to visualize a number of biological processes at the molecular and cellular level. The quest for MRI methods that enable the monitoring of these processes with improved specificity and spatiotemporal resolution has induced a considerable amount of research into the chemistry of contrast agents. A novel class of agents has been developed that is able to report a change in its magnetic properties as a function of a specific parameter in the surrounding microenvironment. The vast majority consist of paramagnetic Gd3+ complexes that enhance the contrast in the MR image upon a change in the local concentration of a biologically relevant ion, such as H+, Ca2+, Zn2+, or Cu2+. This review summarizes their coordination chemistry and further aspects of these responsive paramagnetic complexes and discusses the most recent examples that are described in the literature.},
web_url = {http://www.benthamdirect.org/pages/content.php?CIC/2011/00000001/00000001/0007CIC.SGM},
state = {published},
DOI = {10.2174/1877944111101010076},
author = {Angelovski G{goran}{Department Physiology of Cognitive Processes} and Mamedov I{ilgar}{Department Physiology of Cognitive Processes}}
}

@Article{ KadjaneLA2011,
title = {A straightforward and convenient pathway for the synthesis of functional bismacrocyclic ligands},
journal = {Tetrahedron Letters},
year = {2011},
month = {4},
volume = {52},
number = {14},
pages = {1619-1622},
abstract = {The synthesis of a novel DO3A-based bismacrocyclic ligand is reported. The synthetic pathway involved a series of simple and convenient steps, which can easily provide the desired product in larger quantities than produced in current synthetic procedures. This method enables the facile preparation of binuclear macrocyclic complexes which can be used in MRI, as well as other molecular imaging modalities.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6THS-5230PNH-H-4&_cdi=5290&_user=29041&_pii=S0040403911001821&_origin=&_coverDate=04%2F06%2F2011&_sk=999479985&view=c&wchp=dGLzVlz-zSkWz&md5=f6b2472fe5519148fdaad7bf1a9e34c1&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.tetlet.2011.01.133},
author = {Kadjane P{pkadjane}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Angelovski G{goran}{Department Physiology of Cognitive Processes}}
}

@Article{ KuTLG2011,
title = {fMRI of the Face-Processing Network in the Ventral Temporal Lobe of Awake and Anesthetized Macaques},
journal = {Neuron},
year = {2011},
month = {4},
volume = {70},
number = {2},
pages = {352-362},
abstract = {The primate brain features specialized areas devoted to processing of faces, which human imaging studies localized in the superior temporal sulcus (STS) and ventral temporal cortex. Studies in macaque monkeys, in contrast, revealed face selectivity predominantly in the STS. While this discrepancy could result from a true species difference, it may simply be the consequence of technical difficulties in obtaining high-quality MR images from the ventral temporal lobe. By using an optimized fMRI protocol we here report face-selective areas in ventral TE, the parahippocampal cortex, the entorhinal cortex, and the hippocampus of awake macaques, in addition to those already known in the STS. Notably, the face-selective activation of these memory-related areas was observed although the animals were passively viewing and it was preserved even under anesthesia. These results point to similarly extensive cortical networks for face processing in humans and monkeys and highlight potential homologs of the human fusiform face area.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WSS-52R37RY-C-S&_cdi=7054&_user=29041&_pii=S0896627311002054&_origin=gateway&_coverDate=04%2F28%2F2011&_sk=999299997&view=c&wchp=dGLbVtz-zSkWb&md5=b6710cd9134892714e88e07b1c5ccd35&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.neuron.2011.02.048},
author = {Ku SP{shihpi}{Department Physiology of Cognitive Processes}, Tolias AS{atolias}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Goense J{jozien}{Department Physiology of Cognitive Processes}}
}

@Article{ ChavezBL2011,
title = {Dynamics of excitable neural networks with heterogeneous connectivity},
journal = {Progress in Biophysics and Molecular Biology},
year = {2011},
month = {3},
volume = {105},
number = {1-2},
pages = {29-33},
abstract = {A central issue of neuroscience is to understand how neural units integrates internal and external signals to create coherent states. Recently, it has been shown that the sensitivity and dynamic range of neural assemblies are optimal at a critical coupling among its elements. Complex architectures of connections seem to play a constructive role on the reliable coordination of neural units. Here we show that, the synchronizability and sensitivity of excitable neural networks can be tuned by diversity in the connections strengths. We illustrate our findings for weighted networks with regular, random and complex topologies. Additional comparisons of real brain networks support previous studies suggesting that heterogeneity in the connectivity may play a constructive role on information processing. These findings provide insights into the relationship between structure and function of neural circuits.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6TBN-51N7RMY-1-1&_cdi=5147&_user=29041&_pii=S0079610710000969&_origin=search&_coverDate=03%2F31%2F2011&_sk=998949998&view=c&wchp=dGLzVtb-zSkWA&md5=4a58a2dd648a6d0bb44753aef763c2ce&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.pbiomolbio.2010.11.002},
author = {Chavez M, Besserve M{besserve}{Department Empirical Inference}{Department Physiology of Cognitive Processes} and Le Van Quyen M}
}

@Article{ BerensEGTB2011,
title = {Reassessing optimal neural population codes with neurometric functions},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
year = {2011},
month = {3},
volume = {108},
number = {11},
pages = {4423-4428},
abstract = {Cortical circuits perform the computations underlying rapid perceptual decisions within a few dozen milliseconds with each neuron emitting only a few spikes. Under these conditions, the theoretical analysis of neural population codes is challenging, as the most commonly used theoretical tool—Fisher information—can lead to erroneous conclusions about the optimality of different coding schemes. Here we revisit the effect of tuning function width and correlation structure on neural population codes based on ideal observer analysis in both a discrimination and a reconstruction task. We show that the optimal tuning function width and the optimal correlation structure in both paradigms strongly depend on the available decoding time in a very similar way. In contrast, population codes optimized for Fisher information do not depend on decoding time and are severely suboptimal when only few spikes are available. In addition, we use the neurometric functions of the ideal observer in the classification task to investigate the differential coding properties of these Fisher-optimal codes for fine and coarse discrimination. We find that the discrimination error for these codes does not decrease to zero with increasing population size, even in simple coarse discrimination tasks. Our results suggest that quite different population codes may be optimal for rapid decoding in cortical computations than those inferred from the optimization of Fisher information.},
web_url = {http://www.pnas.org/content/108/11/4423.full.pdf+html},
state = {published},
DOI = {10.1073/pnas.1015904108},
author = {Berens P{berens}{Research Group Computational Vision and Neuroscience}, Ecker AS{aecker}{Research Group Computational Vision and Neuroscience}, Gerwinn S{sgerwinn}{Research Group Computational Vision and Neuroscience}, Tolias AS{atolias}{Department Physiology of Cognitive Processes} and Bethge M{mbethge}{Research Group Computational Vision and Neuroscience}}
}

@Article{ 6736,
title = {Calcium-responsive paramagnetic CEST agents},
journal = {Bioorganic and Medicinal Chemistry},
year = {2011},
month = {2},
volume = {19},
number = {3},
pages = {1097-1105},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6TF8-50J4M9J-1-13&_cdi=5220&_user=29041&_pii=S0968089610006760&_origin=search&_coverDate=02%2F01%2F2011&_sk=999809996&view=c&wchp=dGLbVzz-zSkzk&md5=c8aab830853d6c0893b6bc79f964f314&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.bmc.2010.07.023},
author = {Angelovski G{goran}{Department Physiology of Cognitive Processes}, Chauvin T, Pohmann R{rolf}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Toth E}
}

@Article{ 7097,
title = {Critical In Vitro Evaluation of Responsive MRI Contrast Agents for Calcium and Zinc},
journal = {Chemistry: A European Journal},
year = {2011},
month = {2},
volume = {17},
number = {5},
pages = {1529-1537},
abstract = {The synthesis of two gadolinium(III) complexes that exhibit an increase in proton relaxivity in the presence of added Ca2+ or Zn2+ ions is reported. The complexes increase their hydration state from zero to one following metal-ion binding, confirmed by spectral measurements on the corresponding EuIII complexes. At a field of 1.4&#8197;T and 310&#8197;K, modulation of relaxivity of the order of 30–40&#8201;% was observed in mouse serum in each case. The dissociation constants for Ca2+ and Zn2+ binding were sensitive to the presence of added bicarbonate, and were 450&#8197;&#956;M (Ca2+) and 200&#8197;&#956;M (Zn2+) in serum. Such systems may, therefore, be considered for use as magnetic resonance imaging (MRI) contrast agents to track the restoration of changes in metal-ion concentration in the cerebrospinal fluid of the brain, following neural stimulation.},
web_url = {http://onlinelibrary.wiley.com/doi/10.1002/chem.201001548/pdf},
state = {published},
DOI = {10.1002/chem.201001548},
author = {Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Parker D}
}

@Article{ BesserveM2011,
title = {Extraction of functional information from ongoing brain electrical activity: Extraction en temps-réel d'informations fonctionnelles à partir de l'activité électrique cérébrale},
journal = {IRBM},
year = {2011},
month = {2},
volume = {32},
number = {1},
pages = {27-34},
abstract = {The modern analysis of multivariate electrical brain signals requires advanced statistical tools to automatically extract and quantify their information content. These tools include machine learning techniques and information theory. They are currently used both in basic neuroscience and challenging applications such as brain computer interfaces. We review here how these methods have been used at the Laboratoire d’Électroencéphalographie et de Neurophysiologie Appliquée (LENA) to develop a general tool for the real time analysis of functional brain signals. We then give some perspectives on how these tools can help understanding the biological mechanisms of information processing.},
web_url = {http://www.sciencedirect.com/science?_ob=MiamiImageURL&_cid=277315&_user=29041&_pii=S1959031811000029&_check=y&_origin=&_coverDate=28-Feb-2011&view=c&wchp=dGLzVlV-zSkzk&md5=1da5d166046931defcdba89c4d3498f7/1-s2.0-S1959031811000029-main.pdf},
state = {published},
DOI = {10.1016/j.irbm.2011.01.001},
author = {Besserve M{besserve}{Department Empirical Inference}{Department Physiology of Cognitive Processes} and Martinerie J}
}

@Article{ FiehlerBBBSVFR2011,
title = {Working memory maintenance of grasp-target information in the human posterior parietal cortex},
journal = {NeuroImage},
year = {2011},
month = {2},
volume = {54},
number = {3},
pages = {2401-2411},
abstract = {Event-related functional magnetic resonance imaging was applied to identify cortical areas involved in maintaining target information in working memory used for an upcoming grasping action. Participants had to grasp with their thumb and index finger of the dominant right hand three-dimensional objects of different size and orientation. Reaching-to-grasp movements were performed without visual feedback either immediately after object presentation or after a variable delay of 2–12 s. The right inferior parietal cortex demonstrated sustained neural activity throughout the delay, which overlapped with activity observed during encoding of the grasp target. Immediate and delayed grasping activated similar motor-related brain areas and showed no differential activity. The results suggest that the right inferior parietal cortex plays an important functional role in working memory maintenance of grasp-related information. Moreover, our findings confirm the assumption that brain areas engaged in maintaining information are also involved in encoding the same information, and thus extend previous findings on working memory function of the posterior parietal cortex in saccadic behavior to reach-to-grasp movements.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WNP-515SRFP-7-F&_cdi=6968&_user=29041&_pii=S1053811910012826&_origin=&_coverDate=02%2F01%2F2011&_sk=999459996&view=c&wchp=dGLzVzb-zSkWW&md5=ce2995ae61d933302149ce570e9287a3&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.neuroimage.2010.09.080},
author = {Fiehler K, Bannert M{mbannert}{Department Physiology of Cognitive Processes}, Bischoff M, Blecker C, Stark R, Vaitl D, Franz VH{vf} and R\"osler F}
}

@Article{ 6106,
title = {Brain Hemispheric Structural Efficiency and Interconnectivity Rightward Asymmetry in Human and Nonhuman Primates},
journal = {Cerebral Cortex},
year = {2011},
month = {1},
volume = {21},
number = {1},
pages = {56-67},
abstract = {Evidences of inter-regional structural asymmetries have been previously reported for brain
anatomic regions supporting well described functional lateralization. Here we aimed to
investigate whether the two brain hemispheres demonstrate dissimilar general structural
attributes implying different principles on information flow management. Common left/right
hemisphere structural network properties are estimated and compared for right-handed healthy
human subjects and a non-human primate, by means of three different probabilistic diffusionweighted
MRI fiber tractography algorithms and a graph theory framework. In both the human
and non-human primate the data support the conclusion that the right hemisphere is significantly
more efficient and interconnected than the left hemisphere, whereas the left hemisphere presents
more indispensable regions for the whole brain structural network than the right hemisphere. In
terms of functional principles, this pattern could be related with the fact that the left hemisphere
has a leading role for highly demanding specific process, such as language, which may require
dedicated specialized networks, whereas the right hemisphere has a leading role for more general
process, such as integration tasks, which may require a more general level of interconnection.},
web_url = {http://cercor.oxfordjournals.org/cgi/reprint/bhq058v1},
state = {published},
DOI = {10.1093/cercor/bhq058},
author = {Itturia-Medina Y, Fernandez AP, Morris DM, Canales-Rodriguez EJ, Haroon HA, Penton LG, Augath M{mark}{Department Physiology of Cognitive Processes}, Garcia LG, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Parker GJM and Melie-Garcia L}
}

@Article{ 6724,
title = {Effects of transcranial magnetic stimulation on visual evoked potentials in a visual suppression task},
journal = {Neuroimage},
year = {2011},
month = {1},
volume = {54},
number = {2},
pages = {1375-1384},
abstract = {Transcranial magnetic stimulation (TMS) can non-invasively modify cortical neural activity by means of a time-varying magnetic field. For example, in cognitive neuroscience, it is applied to create reversible “virtual lesions” in healthy humans (usually assessed as diminished performance in a behavioral task), thereby helping to establish causal structure–function relationships. Despite its widespread use, it is still rather unclear how TMS acts on existing, task-related neural activity, potentially resulting in a measurable effect on the behavioral level. Here, we deliver TMS to early visual areas while recording EEG in order to directly characterize the interaction between TMS-evoked (TEPs) and visual-evoked potentials (VEPs). Simultaneously, the subjects&lsquo; performance is assessed in a visual forced-choice task. This allows us to compare the TMS effects on the VEPs across different levels of behavioral impairment. By systematically varying the stimulation intensity, we demonstrate
tha
t TMS strongly enhances the overall visual stimulus-related activity (rather than disrupting it). This enhancement effect saturates when behavior is impaired. This might indicate that the neural coding of the visual stimulus is robust to noise within a certain dynamic range (as indexed by the enhancement). Strong disturbances might saturate this range, causing behavioral impairment. Variation of the timing between the visual stimulus and the magnetic pulse reveals a “constructive interference” between the TEPs and VEPs: The better the overlap between both evoked potentials, the stronger the interaction effect when TMS and visual stimulation are combined. Importantly, however, this effect is uncorrelated with the strength of behavioral impairment.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WNP-50X2NG3-3-G&amp;_cdi=6968&amp;_user=29041&amp;_pii=S1053811910011298&amp;_origin=search&amp;_coverDate=08%2F30%2F2010&amp;_sk=999999999&amp;view=c&amp;wc},
state = {published},
DOI = {10.1016/j.neuroimage.2010.08.047},
author = {Reichenbach A{areichen}{Department Human Perception, Cognition and Action}{Department High-Field Magnetic Resonance}, Whittingstall K{kevin}{Department Physiology of Cognitive Processes} and Thielscher A{thielscher}{Department High-Field Magnetic Resonance}}
}

@Article{ 6999,
title = {Vascularization of Cytochrome Oxidase-Rich Blobs in the Primary Visual Cortex of Squirrel and Macaque Monkeys},
journal = {Journal of Neuroscience},
year = {2011},
month = {1},
volume = {31},
number = {4},
pages = {1246-1253},
abstract = {The close correlation between energy supply by blood vessels and energy consumption by cellular processes in the brain is the basis of blood flow-related functional imaging techniques. Regional differences in vascular density can be detected using high-resolution functional magnetic resonance imaging. Therefore, inhomogeneities in vascularization might help to identify anatomically distinct areas noninvasively in vivo. It was reported previously that cytochrome oxidase-rich blobs in the striate cortex of squirrel monkeys are characterized by a notably higher vascular density (42% higher than interblob regions). However, blobs have so far never been identified in vivo on the basis of their vascular density. Here, we analyzed blobs of the primary visual cortex of squirrel monkeys and macaques with respect to the relationship between vascularization and cytochrome oxidase activity. By double staining with cytochrome oxidase enzyme histochemistry to define the blobs and collagen type IV immunohistochemistry to quantify the blood vessels, a close correlation between oxidative metabolism and vascularization was confirmed and quantified in detail. The vascular length density in cytochrome oxidase blobs was on average 4.5% higher than in the interblob regions, a difference almost one order of magnitude smaller than previously reported. Thus, the vascular density that is closely associated with local average metabolic activity is a structural equivalent of cerebral metabolism and blood flow. However, the quantitative differences in vascularization between blob and interblob regions are small and below the detectability threshold of the noninvasive hemodynamic imaging methods of today.},
web_url = {http://www.jneurosci.org/cgi/reprint/31/4/1246},
state = {published},
DOI = {10.1523/JNEUROSCI.2765-10.2011},
author = {Keller AL{akeller}{Department Physiology of Cognitive Processes}, Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Weber B{bweber}}
}

@Inproceedings{ SigalaSE2011,
title = {Adaptive Properties of Stochastic Memristor Networks: A Computational Study},
year = {2011},
month = {5},
pages = {312-313},
abstract = {A ‘memristor’ is a passive two-terminal circuit element the electric resistance of which depends on the history of the charge that has passed through it. We implemented a platform to simulate adaptive properties of stochastic memristor networks. We showed that such networks follow a stable behavior that diverges from its initial state depending on the history of stimulation. Additionally, we observed that the connectivity patterns of the networks influence their adaptive properties. These results confirm the adaptive properties of statistical memristor networks and suggest that they can be potentially used as complex and self-assembled ‘learning machines’.},
file_url = {fileadmin/user_upload/files/publications/2011/FET-2011-Sigala.pdf},
web_url = {http://www.fet11.eu/},
publisher = {Elsevier},
address = {Amsterdam, Netherlands},
booktitle = {Procedia Computer Science Volume 7},
event_name = {2nd European Future Technologies Conference and Exhibition (FET 11)},
event_place = {Budapest, Hungary},
state = {published},
DOI = {10.1016/j.procs.2011.09.021},
author = {Sigala R{sigala}{Department Physiology of Cognitive Processes}, Smerieri A and Erokhin V}
}

@Inproceedings{ 7047,
title = {Finding dependencies between frequencies with the kernel cross-spectral density},
year = {2011},
month = {5},
pages = {2080-2083},
abstract = {Cross-spectral density (CSD), is widely used to find linear dependency between two real or complex valued time series. We define a non-linear extension of this measure by mapping the time series into two Reproducing Kernel Hilbert Spaces. The dependency is quantified by the Hilbert Schmidt norm of a cross-spectral density operator between these two spaces. We prove that, by choosing a characteristic kernel for the mapping, this quantity detects any pairwise dependency between the time series. Then we provide a fast estimator for the Hilbert-Schmidt norm based on the Fast Fourier Trans form. We demonstrate the interest of this approach to quantify non-linear dependencies between frequency bands of simulated signals and intra-cortical neural recordings.},
web_url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=5946735},
publisher = {IEEE},
address = {Piscataway, NJ, USA},
event_name = {IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP 2011)},
event_place = {Praha, Czech Republic},
state = {published},
ISBN = {978-1-4577-0538-0},
DOI = {10.1109/ICASSP.2011.5946735},
author = {Besserve M{besserve}{Department Empirical Inference}{Department Physiology of Cognitive Processes}, Janzing D{janzing}{Department Empirical Inference}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Sch\"olkopf B{bs}{Department Empirical Inference}}
}

@Inbook{ Schuz2011_2,
title = {Die Macht der Fasern: Hirnforschung von und mit Valentin
Braitenberg},
year = {2011},
pages = {90-101},
editor = {Hosp, I. , A. Schüz, Z. Braitenberg},
publisher = {Edition Raetia},
address = {Bolzano, Italy},
booktitle = {Tentakel des Geistes: Begegnungen mit Valentin Braitenberg},
state = {published},
ISBN = {978-88-7283-403-9},
author = {Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}}
}

@Poster{ KayserLP2011,
title = {A computational proof of concept for how slow rhythms could serve as internal reference frames for decoding firing patterns in sensory cortices},
year = {2011},
month = {11},
volume = {41},
number = {480.40},
abstract = {The coding properties of sensory neurons are typically examined after aligning neural and sensory events relative to a laboratory-based temporal reference, such as the computer clock controlling sensory stimulus presentation and data acquisition. While this approach often reveals considerable stimulus information in finely timed response patterns (e.g. in millisecond precise spike timing), it remains unclear whether the brain may exploit such temporal information as it does not have access to the laboratory-based temporal reference frame. Rather, the brain has to rely on an intrinsic temporal reference frame to decode temporal patterns of spiking responses. This raises the questions of whether, and how, the brain can compute temporal patterns of neural responses based on an internal time reference frame.
One candidate mechanism for such an internal reference frame is provided by slow rhythms, which are ubiquitous in sensory cortical local field potentials (LFPs). We here show that theta-band rhythms in sensory cortices have the key features to serve as an internal reference for the efficient readout of informative temporal response patterns. To this end we analyzed neural responses to naturalistic stimuli recorded in auditory and visual cortices of macaque monkeys using computational methods of stimulus decoding and information theory. We found that the phase of theta LFPs (4-10Hz) can be used to group action potentials of single neurons and populations thereof into response patterns that carry similar levels of single trial stimulus information as obtained using the laboratory-based reference frame: using a phase-based reference frame recovered 70-90% of the information available when decoding the same responses using the laboratory based reference frame. This is possible because slow rhythms robustly entrain to the sensory environment both during isolated stimuli and during continuous stimulation periods. Importantly, this phase-based reference frame allows for sufficient temporal precision to create phase-aligned responses on those time scales on which neural responses are most informative about complex stimuli (here a few tens of milliseconds).
These findings provide a direct computational proof of concept for the hypothesis that slow rhythmic activity may serves as internal reference frame for information coding and thereby bolster speculations about a mechanistic function of slow rhythmic activity in sensory cortical information coding.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Poster{ SchindlerKB2011,
title = {Decoding egocentric space in human posterior parietal cortex using fMRI},
year = {2011},
month = {11},
volume = {41},
number = {800.21},
abstract = {In our subjective experience, there is a tight link between covert visual attention and ego-centric spatial attention. One key difference is that the latter can extend beyond the visual field, providing us with an accurate mental representation of an object’s location relative to our body position. A neural link between visual and ego-centric spatial attention is suggested by lesions in parietal cortex, that lead not only to deficits in covert visual attention, but frequently also to a disorder of ego-centric spatial awareness, known as hemi-spatial neglect. While parietal involvement in covert visual spatial attention has been much studied, relatively little is known about mental representations of the unseen space around us.
In the present study we examined whether also unseen spatial locations beyond the visual field are represented in parietal activity, and how they are related to retinotopic representations. We employed a novel virtual reality (VR) paradigm during functional magnetic resonance imaging (fMRI), whereby observers were prompted to draw their spatial attention to the position of one of eight possible objects located around them in an octagonal room. By changing the observers’ facing direction every few trials, the egocentric location of objects was disentangled from their absolute position and from the objects’ identity. Thus, mental representations of egocentric space surrounding the observer were sampled eight-fold.
De-coding results of a multivariate pattern analysis classifier (MVPA), but not univariate results, showed that egocentric spatial directions were specifically represented in parietal cortex. These representations overlapped only partly with visually driven retinotopic activity.
Our results thus show that parietal cortex codes not only for retinotopic and visually accessible space, but also for egocentric locations of the three-dimensional space surrounding us, including unseen space.},
web_url = {http://www.sfn.org/AM2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Schindler A{aschindler}{Department Physiology of Cognitive Processes}, Kleiner M{kleinerm}{Department Human Perception, Cognition and Action} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ ForroLE2011,
title = {Distribution of a large spindle-shaped neuron in the anterior agranular insula in the macaque monkey},
year = {2011},
month = {11},
volume = {41},
number = {817.07},
abstract = {We report the presence of a large spindle-shaped neuron in layer 5b in the anterior agranular insula in the rhesus and cynomolgus macaque monkeys. This neuron shares numerous characteristics with the von Economo neuron (VEN), a large spindle-shaped neuron that is present in layer 5b in the anterior insula in humans and great apes and that appears to have a crucial role in self-awareness and social cognition in humans. Thus, like the VEN, the large spindle-shaped neuron in the macaque has an elongate perikaryon that is symmetrical about its height and width; has a unique basal dendrite that is proximally as thick as its apical dendrite; is larger or as large as the local pyramidal neurons and much larger than the fusiform neuron in layer 6; and expresses the neurofilament protein SMI-32 and the serotonin receptor 2b. Golgi material reveals that its dendrites have all the characteristics of a projecting neuron; and it is retrogradely labeled with neuronal tracer injected at a distant site. It is consistently mingled with fork neurons. Finally, the portion of the insula that contains this spindle-shaped neuron in the macaque is located, like in humans and great apes, in a portion of the agranular insula that is anterior to the limen and medial to the superior sulcus of the insula. We conclude that the large spindle-shaped neuron in the macaque insula is anatomically homologous with the hominoid VEN, and that the anterior agranular insula in the macaque is at least in part anatomically homologous with the human anterior insula (or frontoinsula). Further evidence from this laboratory indicates that the VEN is also present in a similar portion of the anterior agranular insula in other species of monkeys and in lesser apes (Evrard et al., this meeting). The VEN is smaller and much less frequent in the macaque than in human; it is therefore unlikely that its role in the macaque is as evolved as it appears to be in human. Nevertheless, the present demonstration offers a unique opportunity to examine in the laboratory the hodology and primal function of a brain region that appears to be central to human self-awareness and in which malformation, lesion or degeneration have a dramatic impact on human bodily and emotional feelings as well as social interaction.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Forro T{tforro}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Evrard HC{evrard}{Department Physiology of Cognitive Processes}}
}

@Poster{ ZaldivarLvZLR2011,
title = {Dopaminergic modulation of the early visual system of non-human primates and its underlying neuronal and hemodynamic changes},
year = {2011},
month = {11},
volume = {41},
number = {175.01},
abstract = {Dopamine (DA) is thought to have a gating role in the communication between thalamus and primary sensory areas. In the primary visual pathway D2-receptors (D2Rs) are predominantly found in lateral geniculate nucleus (LGN) while D1-receptors (D1Rs) show higher density in primary visual cortex. D1Rs have a facilitating effect on neuronal processing whereas D2Rs show a dampening effect. Given their differences in anatomical distribution and functionality the two dopaminergic (DAergic) receptors may have a differential effect on thalamocortical information transfer. Here we set out to investigate DAergic impact on V1 by using combined fMRI and neurophysiological measurements in anesthetized non-human primates, during systemic application of L-DOPA (LD: 2.1 mg/kg) and Carbidopa (C: 0.5 mg/kg). Our results show that the stimulus-induced modulation of the BOLD signal decreases by 45 ± 8% for 10 ± 3 min (n=6, p < 0.05). This decrease is concomitant with an improvement in signal-to-noise ratio (SNR) in multi unit activity (MUA: 900-3200 Hz) as well as decrease in CV (p<0.05) of the theta (4-8 Hz), low-gamma (20-60 Hz) and gamma (65-120 Hz) bands of LFP. In contrast, local application of DA in V1 did not induce any changes in neuronal activity indicating that the observed effects are most probably mediated by D2Rs of LGN. DAergic neuromodulation improved SNR of the neuronal recordings in V1 which reflects a sparse and dampened firing pattern with little background interferences. These findings suggest that the visual inputs are attenuated by the local DAergic circuitry of LGN (D2Rs) generating sparse and precise neuronal firing in V1. At the same time, however, the reduced mass-activity appears to reduce the energy demands, and the stimulus-induced modulation of the BOLD signal. Our findings confirm the important role of D2Rs in gating inputs to primary visual cortex by achieving sparse and adequate neuronal firing.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Zaldivar D{dzaldivar}{Department Physiology of Cognitive Processes}, Li J{juan}{Department Physiology of Cognitive Processes}, von Pf\"ostl V{vpfoestl}{Department Physiology of Cognitive Processes}, Zhang X{xiaozhe}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rauch A{arauch}{Department Physiology of Cognitive Processes}}
}

@Poster{ ReinlB2011,
title = {Dynamic faces: fMRI reveals timeline specific responses to facial expression changes},
year = {2011},
month = {11},
volume = {41},
number = {487.14},
abstract = {In every day life we are usually exposed to dynamically changing faces rather than to their static snapshots. Despite this, the vast majority of neurophysiology and neuroimaging studies have examined responses to static pictures of faces. Therefore, only little is known about the extent to which neural circuitries exist that are specialized to process dynamic aspects of faces, or whether dynamic faces are processed the same way as static ones. One difficulty in answering this question lies in appropriate control stimuli between static and dynamic conditions, as the latter tend to elicit overall more neural activity. In the present study we circumvented this problem by testing for neural responses that are sensitive to the timeline of facial expression changes. We used a 2x2 factorial design, showing different types of video recordings of facial expressions in an event-related fMRI study. We varied the emotional content (factor ,,emotion“) by using emotional expressions that either increased or decreased in the intensity of fear. Additionally, both types of movies were then played forward in their original timeline (real sequence) or backward (artificial sequence), defining the second factor ,,time“. Our aim was to identify brain areas that react specifically to the provided frame-sequence (time effect: real vs. artificial) or to the differences in the displayed emotion-direction (emotion effect: increase vs. decrease). Time-sensitive responses were found in the superior frontal gyrus (STS), in the occipital face area (OFA) and in a prefrontal set of regions, but not in the fusiform face area (FFA), with generally higher responses to real as opposed to artificial timelines. Emotion-sensitive responses were identified in STS (with larger responses to increasing fear), as well as in a part of the right inferior frontal gyrus belonging to the action observation network (with larger responses to decreasing fear). Thus, dynamic face stimuli elicited timeline specific activity in particular parts of the classic face-processing network (STS and OFA, but not FFA), as well as in higher-level cognitive regions that most likely interpret the meaning of time-dependent information. Our results therefore provide evidence for mid- as well as high-level time-sensitive detectors in human face processing.},
web_url = {http://www.sfn.org/AM2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Reinl M{mreinl}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ VenkateshRGPM2011,
title = {EEG signals are informative for individual cue-response combinations in a visuomotor task},
year = {2011},
month = {11},
volume = {41},
number = {914.14},
abstract = {The execution of complex behavior requires the coordinated action of discrete neural populations. The dynamic interaction of distributed populations are studied by mesoscopic and macroscopic measures of brain activity such as LFP and EEG signals which reflect the summated responses of neural groups to cognitive events. We wanted to investigate if a quantitative measure of modulations in oscillatory components with specific task components and demands can be derived. A sensorimotor task paradigm was implemented where distinct visual cues indicate distinct motor responses to determine if modulations in oscillations can be tuned to specific cue-response combinations.
Two monkeys were trained to perform a visuo-motor task which involved moving a lever with their right hand cued by moving visual stimuli. Movement direction and velocity of sine wave gratings were trained to be associated with a target position of the manipulandum.
Multi-area EEG signals were acquired from implanted electrodes above visual, parietal, sensorimotor and premotor areas. The time frequency spectra of the EEG signals was characterized by continuous wavelet transform. The time frequency spectrum displays dominant power in the 10-30 Hz bands although significant modulation is also present in 1-10 Hz and 45 - 80 Hz bands. We investigated the stimulus and motor response specificity of oscillations by computing mutual information between the cue or motor response and specific frequency components of the oscillatory signal.
We find that information is higher in left hemisphere electrodes above sites related to the task such as visual and sensorimotor electrodes (statistically significant for the 1-8 Hz and 45-60 Hz band), reflecting the usage of the right hand for motor response. The peak mutual information was found in the lower frequency bands such as the 1-8 Hz band with a mean value of 0.16 bits averaged across channels and timebins. The higher frequency bands such as the 45-60 Hz band also carry information about the cues although at a lower magnitude (mean value of 0.04 bits).
We found that cues can be distinguished based on the differences in spectral power in certain channels activated by the task. Information about cue or task attributes is carried in discrete frequency bands with the lower frequency bands being most informative.
Estimating mutual information can provide a quantitative measure of tuning of defined frequency components of EEG to stimulus or task attributes. EEG signals which reflect the coherent activity of many neural populations carry information in their frequency structure about how stimulus processing- behavior production drives activation of multiple brain areas.},
web_url = {http://www.sfn.org/am2011/index.aspx?pagename=final_program},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Venkatesh V{vvenkatesh}{Department Physiology of Cognitive Processes}, Rulla S{rulla}{Research Group Neural Population Imaging}, Gotthardt S{gotthardt}{Department Physiology of Cognitive Processes}, Panzeri S{stefano} and Munk M{munk}{Department Physiology of Cognitive Processes}}
}

@Poster{ EvrardZSL2011,
title = {Large spindle-shaped neurons in the anterior insula in lesser apes and monkeys},
year = {2011},
month = {11},
volume = {41},
number = {817.15},
abstract = {We report the presence of a large spindle-shaped neuron in layer 5b in the agranular insula in several different species of Old World monkeys and in two species of lesser apes. The Old World monkeys included five rhesus and five cynomolgus macaques, two baboons, two mangabeys, two langurs, one colobus, one blue monkey and one patas monkey. The lesser apes included two gibbons and one siamang. The large spindle-shaped neuron found in all these species shared numerous characteristics with the von Economo neuron (VEN), a large spindle-shaped neuron that is present in layer 5b in the anterior insula in humans and great apes and that appears to have a crucial role in self-awareness and social cognition in humans. Thus, the large spindle-shaped neuron in the monkeys, gibbon and siamang had an elongate perikaryon that was symmetrical about its height and width; had a unique basal dendrite that was proximally as thick as its apical dendrite; was as large or larger than local pyramidal neurons and much larger than the small fusiform neurons in layer 6; was consistently mingled with fork neurons; and was located, as in humans, in a restricted portion of the agranular insula, anterior to the limen and medial to the superior limiting sulcus of the insula. Taken together with evidence from a more detailed analysis in the macaque monkey (Forro et al., this meeting), we conclude that the large-spindle shaped neuron found in the Old World monkeys and lesser apes is anatomically homologous with the hominoid VEN. A preliminary examination of the anterior agranular insula in several species of New World monkeys did not reveal the presence of the large spindle-shaped neuron, except for a few isolated neurons found in one spider monkey. The present findings suggest that the VEN emerged much earlier than previously proposed and was present already at least in a common ancestor of the cercopithecoids and hominoids. Although being much less numerous and smaller than in humans, the VEN in monkeys and lesser apes likely shares some primal functions and connections with the VEN in humans. Future comparative and quantitative analyses of the distribution of the VEN across primate species living in different ecological niches and having different behaviors and social organizations might provide valuable information regarding the evolutive mechanisms that lead to the marked development and crucial role of VEN in humans.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Evrard HC{evrard}{Department Physiology of Cognitive Processes}, Zilles K, Sherwood CC and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ CrockerKPLP2011,
title = {Low frequency local field potentials in the inferior convexity of the macaque prefrontal cortex convey visual information during anesthesia},
year = {2011},
month = {11},
volume = {41},
number = {484.13},
abstract = {The inferior convexity of the macaque prefrontal cortex (icPFC), the cortical area anterior to the arcuate and inferior to the principal sulcus, consists the final endpoint of the ventral visual stream. It has been suggested that the icPFC is involved in higher order processing of non spatial visual information like stimulus selection, attention and working memory. However, early findings demonstrated that spiking activity in the icPFC is also modulated by visual stimulation during anesthesia. Here we used multi-electrode recordings to study in more detail the neural coding of visual information as well as the spatial distribution of this information in the icPFC of the anesthetized macaque. We recorded local field potentials (LFP) and multi and single unit spiking activity, and calculated the Shannon (mutual) information between these neurophysiological signals and a dynamic movie stimulus. We found that the phase of low frequency (1-10Hz) local field potentials (LFP) conveyed significant visual information about the movie. Significant information was also conveyed by the energy of the low frequency (1-10Hz) LFP. However the mutual information between the energy of the 1-10Hz LFP and the movie was an order of a magnitude less than the information conveyed by the phase. Information in the LFP phase was distributed evenly across all recorded sites, with almost all channels lying between 50% and 150% of the average amount of information. However, the information carried by the LFP amplitude was highly clustered around a small group of electrodes. Almost half of the recorded sites carried less than 50% of the mean information across electrodes, and around 15 recorded sites had more than 3 times the average information. High frequency LFP phase and energy were highly variable across repeated presentations of the movie and were thus non-informative. Similarly, multi unit and single unit spiking activity pattern or rate codes conveyed no information about the movie. Our results show that input and intracortical processing in the icPFC during anesthesia conveys significant information about dynamic visual stimuli.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Crocker B{bcrocker}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Panzeri S{stefano}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}}
}

@Poster{ PanzeriMKMQML2011,
title = {Neurons in primary visual cortex encode naturalistic visual information using multiple temporal scales},
year = {2011},
month = {11},
volume = {41},
number = {483.10},
abstract = {Natural visual environments contain a variety of continuously changing visual features . In order to represent the richness of such environments, neurons in visual areas need to encode information both about “what” aspects of the visual world (for example, the level of contrast) and how these aspects change over time. So far, little is known about how the responses of visual cortical neurons can encode both types of information concurrently.
Here we explored the hypothesis that aspects of visual features defined on different time scales are to some extent encoded by different aspects of the neural responses. We recorded single unit activity and LFPs in primary visual cortex of anaesthetized macaques during the binocular presentation of naturalistic color movies. By means of computational analysis, we extracted two visual features from the area of the movie inside the receptive fields (RFs) of each single neuron. The first was the Michelson contrast in the RF. The second was a form of temporal contrast, quantifying the average frame to frame variations of pixel luminance in the RF. We then used information theoretic analysis to investigate systematically which types of neural codes carried information either about the current value of these features in each frame or about the time course of these features on slower time scales.
We found that spike rates encoded both the current value and the frame by frame change of the Michelson contrast, but did not encode information about the time course of these features on slower time scales. We then considered the information carried by the “phase of firing”, defined as the timing of spikes measured with respect to the phase of low frequency [1-4 H] Local Field Potential fluctuations. The phase of firing carried information about the temporal changes of contrast over a time scale of several hundred milliseconds (which are the scales carrying the most power in natural movies), but did not carry information about the current value of contrast in each frame or about its frame to frame variations.
These results demonstrate that different aspects of visual features, such as their current value and their dynamics on slow time scales, are represented in complementary neural codes operating on different time scales. They hence suggest that the nervous system uses multiplexing to keep a simultaneous representation of several important aspects of the external world.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Panzeri S{stefano}, Mazzoni A, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Quian Quiroga R, Martinez J and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ LiZvSZLR2011,
title = {Nicotinic modulation of the early visual system and its underlying neuronal and metabolic changes},
year = {2011},
month = {11},
volume = {41},
number = {864.17},
abstract = {In macaques, cholinergic subreceptors of nicotine (nAChRs) are predominantly found in the excitatory afferents of the primary visual cortex (V1, layer 4c) originating from the lateral geniculate nucleus (LGN). This strategic termination pattern allows nicotine to up regulate thalamocortical activity, while in parallel activity outside layer 4c can be down regulated by nicotinic effects on GABAergic inhibition. In addition to this gain-modulating role, nicotine has also distinct neuroprotective effects. Here, we have examined whether such neuroprotective effects could be at least partially explained by the gain modulation itself which tunes neuronal networks to a most efficient input-output mode with little other interferences. We investigated nicotinic effects (systemic: 0.2mg/kg) in V1 by neurophysiological recordings using multi-laminar probes and sampling of intracortical glutamate, GABA and glutamine by microdialysis in anesthetized non-human primates. Multi unit activity (MUA: 900-3200 Hz) and gamma (65-120 Hz) activity showed an improved signal-to-noise ratio (SNR) while theta activity (4-8Hz) was significantly reduced (p<0.5). The neurochemical analysis on the other hand showed increased concentrations of GABA (+40%) while glutamate (-60%) and glutamine levels (-50%) were reduced. Taken together nicotine shifts the ratio between glutamate and GABA clearly to GABA inducing inhibitory effects which reduce excitation and result in low glutamate levels. The decrease in excitatory neuronal activity is reflected in the reduced theta activity and the improved SNR in MUA and the gamma band resulting in an efficient input-output relation due to little excitatory interferences. The low levels of glutamine are most likely caused by the increased synthesis of GABA for which glutamine is a metabolic precursor. The neuroprotective effects of nicotine can be explained by the reduction of glutamate sparing neuronal networks from abundant excitatory activity resulting in excitotoxic effects by glutamate itself and other potentially toxic metabolites.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Li J{juan}{Department Physiology of Cognitive Processes}, Zaldivar D{dzaldivar}{Department Physiology of Cognitive Processes}, von Pf\"ostl V{vpfoestl}{Department Physiology of Cognitive Processes}, Serr N{nserr}{Department Physiology of Cognitive Processes}, Zhang X{xiaozhe}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rauch A{arauch}{Department Physiology of Cognitive Processes}}
}

@Poster{ MagriMLP2011_2,
title = {Optimal Band Separation of Local Field Potentials},
year = {2011},
month = {11},
volume = {41},
number = {841.21},
abstract = {Local Field Potentials (LFPs) are a complex signal which captures multiple neural contributions, from dendrosomatic dipoles generated by synaptic activity to non-synaptic slow activity such as voltage-dependent membrane oscillations and spike afterpotentials. LFPs exhibit a broadband spectral structure which is traditionally partitioned into distinct frequency bands, initially introduced in the human EEG literature, which are thought to originate from different types of neural events triggered by different processing pathways, such as sensory pathways or neuromodulation. However, the exact frequency boundaries of these processes are not known and, as a result, the frequency bands are often selected based on intuition, previous literature and visual inspection of the data.
To address the problem of the arbitrariness of band selection, we defined and implemented numerically a rigorous method to define the number of LFP frequency bands and their boundaries. The criterion chosen for setting the boundaries is to maximize the information about an external correlate carried by the LFP partition. The number of bands is set as the minimum number of bands necessary to provide all the information carried by the LFPs.
We applied the partitioning method to the LFPs recorded from primary visual cortex of anaesthetized macaques, and we determined the optimal band partitioning of the [1-250 Hz] LFP range that describes the encoding of naturalistic visual stimuli. We started by partitioning the LFP range into two bands and we successively increased the number of bands in the partition. Four bands (three optimal boundaries) seemed to be enough to extract most stimulus information carried by the LFPs. The first optimal boundary was in the range 50-60 Hz. It partitioned the LFP response into two components - the low frequency range and the gamma range - which have been found (Belitski et. al. 2008) to convey independent information about the natural movie correlate. The second optimal boundary was between 90 and 110 Hz. It subdivided the gamma range into low- and high- gamma frequencies, consistent with recent reports (Gieselmann and Thiele 2008, Ray and Maunsell 2010) that low and high gamma signals may reflect distinct neural processes. The third and last boundary was at approximately 25 Hz. It subdivided the <50 Hz LFP range into two components, one (<12 Hz) highly informative about the visual stimulus and one which was found not to correlate with the visual stimulus.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Magri C{cmagri}{Department Physiology of Cognitive Processes}, Mazzoni A, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Poster{ ZaretskayaB2011,
title = {Parietal cortex mediates perceptual grouping across space: Evidence from fMRI and TMS},
year = {2011},
month = {11},
volume = {41},
number = {800.14},
abstract = {One of the key real-world challenges to our visual system is posed by cluttered scenes and occluded objects. To make sense of such scenes, local elements belonging to the same object need to be perceptually grouped, also referred to as spatial binding problem. However, it remains unknown how and where in the brain the local information is grouped together to give rise to a holistic percept. In the current study we addressed this question with a novel bistable motion stimulus developed by Anstis and Kim (2011) that consists of four pairs of dots coherently moving on a circular path. The stimulus causes perception to alternate spontaneously between two interpretations: local dot motion and global motion of two imaginary squares. Using functional magnetic resonance imaging (fMRI), we found that activity in the right parietal cortex correlated specifically with global as compared to local perception periods. To test for a causal role of parietal function in perceptual grouping, we used transcranial magnetic stimulation (TMS) to temporarily disrupt activity in two subregions of the parietal cortex. TMS over one of the subregions - the right anterior intraparietal sulcus (IPS) - specifically affected the global percept durations without affecting the local ones. Our results provide causal evidence that IPS may play a crucial role in perceptual grouping of local elements into a holistic percept, suggesting it to be a common anatomical locus of attention, perceptual grouping and perceptual selection processes.},
web_url = {http://www.sfn.org/AM2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Zaretskaya N{nataliya}{Department Physiology of Cognitive Processes}{Department High-Field Magnetic Resonance} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ PapanikolaouKSKPSLS2011,
title = {Population receptive field mapping in human subjects with lesions of the visual cortex},
year = {2011},
month = {11},
volume = {41},
number = {851.07},
abstract = {Damage to the primary visual cortex (V1) as a result of stroke typically leads to the inability to perceive visual stimuli in the affected region of the contralateral visual hemifield (scotoma). However, in spite of this, several higher visual areas have been shown to be modulated by visual stimuli presented inside the scotoma. A much debated issue is whether adult visual cortex is able to reorganize after injury, and if so, what is the extent and the mechanism of the observed reorganization. Here we use functional magnetic resonance imaging (fMRI) methods to study visual cortex reorganization after injury in adult human subjects. To this end we applied a method introduced by Dumoulin and Wandell (Dumoulin SO, Wandell BA, Population receptive field estimates in human visual cortex, Neuroimage 39, 2008), which uses functional magnetic resonance imaging (fMRI) to measure the aggregate receptive field properties of neuronal populations voxel by voxel in the visual cortex. FMRI measurements were obtained during the presentation of a moving bar stimulus which traversed the visual field while the subjects were fixating and these measurements were used to derive an estimate of the voxel based population receptive field centre and radius. We studied several subjects with quadrandanopsia and hemianopsia resulting from cortical lesions and compared them to the range of measurements obtained from a group of normal controls. In general, retinotopic maps in the patients’ spared early visual cortex appear to be consistent with retinotopic maps obtained in control subjects. The organization of higher level visual areas, such as V3a/b and MT show preliminary some differences compared to those of normal subjects. Also preliminary results on the population receptive field size of some of the patients’ spared visual areas show deviations from the normal range of population receptive field sizes derived from the control subjects. We are in the process of obtaining further measurements to confirm these findings and to assess to what degree they correspond to cortical reorganization.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Papanikolaou A{amalia}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Shao Y{yshao}{Department Physiology of Cognitive Processes}, Krapp E, Papageorgiou E, Schiefer U, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Smirnakis SM}
}

@Poster{ ShaoKPALS2011,
title = {Population receptive field measurements in visual cortex of macaque monkeys},
year = {2011},
month = {11},
volume = {41},
number = {851.09},
abstract = {Visual receptive fields have dynamic properties that may change with the conditions of visual stimulation or with the state of chronic visual deprivation. We used 4.7 Tesla functional magnetic resonance imaging (fMRI) to study the visual cortex of two adult normal macaque monkeys and one with binocular central retinal lesions due to a form of juvenile macular degeneration (D06). FMRI experiments were performed under light remifentanyl induced anesthesia (Logothetis et al. Nat. Neurosci. 1999). Standard moving horizontal/vertical bar stimuli were presented to the subjects and the population receptive field (pRF) method (Dumoulin and Wandell, Neuroimage 2008) was used to measure retinotopic maps and pRF sizes in early visual areas. In addition we used a new spatiotemporal dynamic modulation method to measure pRF sizes as comparison. In general fMRI measurements from the normal monkeys agree with electrophysiological results in the literature, with fMRI pRF sizes and electrophysiology measurements showing similar trends. For the macular degeneration monkey (D06), the size and location of the fMRI defined lesion projection zone in early visual areas is consistent with the retinotopic projection of the retinal lesion. No significant activity was found within V1 LPZ of D06, and the retinotopic organization of the non-deafferented V1 periphery is regular without distortion. Higher level visual areas of D06 (V5/MT) show more extensive activation than areas of control monkeys with an artificial scotoma (to obscure part of the stimuli from the visual field as a simulation of the real scotoma) of comparable size. PRF sizes in the non-deafferented V5/MT of monkey D06 are on average slightly smaller than controls. Further investigation using fMRI and standard electrophysiology methods is in progress.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Shao Y{yshao}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Papanikolaou A{amalia}{Department Physiology of Cognitive Processes}, Augath M{mark}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Smirnakis SM}
}

@Poster{ FrankeAMGOM2011,
title = {Sorting synchronous spikes from 3-dimensional tetrodes},
year = {2011},
month = {11},
volume = {41},
number = {627.11},
abstract = {Cooperativity of cortical neurons often expresses in synchronous spike discharge. As neighboring neurons are more densely connected than neurons recorded from different micro electrodes, synchronous firing is more prevalent. Recording from local groups of neurons with conventional micro electrodes bears the difficulty that sorting the activity of spikes from different cells is error prone, because so far temporally overlapping spikes could not be separated reliably. Using tetrodes with a highly reproducible 3-dimensional structure, a single spike can be recorded on more than one channel. This provides additional information about the origin of the action potential ("stereo-effect") and can be used to improve sorting performance. In the case of overlapping spikes additional information provided by the stereo-effect can be even more valuable to detect and correctly resolve the overlap.
Here, we present simultaneous intracellular and extracellular recordings of two neurons for the assessment of spike sorting performance. Two pyramidal neurons in slices of rat visual cortex were recorded intracellularly, stimulated in a way to produce synchronous or near synchronous spiking activity and also recorded extracellularly with a 3D multichannel electrode (“tetrode”). Spike sorting was carried out on the extracellular data only. The intracellular recording is then used to asses the sorting performance. The algorithm employed here uses linear filters derived from the prototypical spike waveforms ("templates"). The filter outputs can be interpreted in a Bayesian sense and are able to detect and resolve overlapping spikes. We show that - if for every neuron its template is estimated using the available ground truth information - overlapping spikes can be reliably separated with the same performance as non overlapping spikes (<5% error rate). Separation performance is greatly improved by the additional information provided by multi electrode recordings confirming the results for non overlapping spikes. The finding that classical clustering based methods perform poorly for overlapping spikes is also confirmed. Furthermore, the inability of ICA to resolve overlapping spikes is demonstrated, even if the correct independent component basis vectors are estimated with the available ground truth information.
In conclusion, we show that the proposed methods can be used to successfully analyze synchronous and near synchronous spikes recorded from neurons at the same tetrode, both in-vitro and in macaque prefrontal cortex.},
web_url = {http://www.sfn.org/am2011/index.aspx?pagename=final_program},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Franke F{ffranke}{Department Physiology of Cognitive Processes}, Alle H, Meier P, Geiger J, Obermayer K and Munk MH{munk}{Department Physiology of Cognitive Processes}}
}

@Poster{ PanagiotaropoulosBCKTPL2011,
title = {Spatiotemporal mapping of rhythmic activity in the inferior convexity of the macaque prefrontal cortex},
year = {2011},
month = {11},
volume = {41},
number = {239.15},
abstract = {The inferior convexity of the macaque prefrontal cortex (icPFC) is known to be involved in higher order processing of sensory information mediating stimulus selection, attention and working memory. Until now, the vast majority of electrophysiological investigations of the icPFC employed single electrode recordings. As a result, relatively little is known about the spatiotemporal structure of neuronal activity in this cortical area. Here we study in detail the spatiotemporal properties of local field potentials (LFP's) in the icPFC using multi electrode recordings during anesthesia. We computed the LFP-LFP coherence as a function of frequency for thousands of pairs of simultaneously recorded sites anterior to the arcuate and inferior to the principal sulcus. We observed two distinct peaks of coherent oscillatory activity between approximately 4-10 and 15-25 Hz. We then quantified the instantaneous phase of these frequency bands using the Hilbert transform and found robust phase gradients across recording sites. The dependency of the phase on the spatial location reflects the existence of traveling waves of electrical activity in the icPFC. The dominant axis of these traveling waves roughly followed the ventral-dorsal plane. Preliminary results show that repeated visual stimulation with a 10s movie had no dramatic effect on the spatial structure of the traveling waves. Traveling waves of electrical activity in the icPFC could reflect highly organized cortical processing in this area of prefrontal cortex.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Besserve M{besserve}{Department Empirical Inference}{Department Physiology of Cognitive Processes}, Crocker B{bcrocker}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Tolias AS{atolias}{Department Physiology of Cognitive Processes}, Panzeri S{stefano} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ BrasseletPLK2011,
title = {Stimulus encoding in temporal firing patterns relative to population-derived stimulus onset times},
year = {2011},
month = {11},
volume = {41},
number = {480.60},
abstract = {The information carried by sensory neurons is usually examined after aligning individual spikes relative to the physical stimulus onset. However, the brain does not know this precise onset, but rather has to rely on intrinsically defined reference points to decode temporal activity patterns. This raised doubts about the relevance of stimulus information in millisecond precise spike times and promoted speculations about intrinsic references. We here demonstrate that a sub-population of neurons in auditory cortex may provide such a reliable reference system.
We recorded the responses of 70 neurons in primary auditory cortex of alert macaque monkeys in response to 12 naturalistic sounds. Within this dataset, we found a population (‘A’) of 17 neurons (24%) with the distinct property that these neurons responded to each stimulus on nearly every trial (at least 92% of trials) with short response onset latency (below 20ms). This property was not shared by the other neurons (population ‘B’), which responded only to a subset of stimuli and which often exhibited large variability in their latency. We then assessed the amount of stimulus information carried by ‘B’ neurons when referenced to i) the physical stimulus onset, ii) the onset latency of a simultaneously recorded ‘A’ neuron, and iii) the onset latency (if existent) of a simultaneously recorded ‘B’ neuron. Stimulus information was defined as the cumulative information in binary 5-spike patterns (3ms bins) over the first 100ms stimulus. Using a ‘B’ neuron as reference allowed recovering only approximately 50% of the information available when using the stimulus onset as reference, but using an ‘A’ neuron as reference recovered more than 75% of this information. We then constructed a hypothetical population of N ‘A’ neurons with the same latency trial-to-trial-jitter and cross-correlation as measured in real ‘A’ neurons, and we systematically quantified the information carried by B neurons when referenced to this population. This revealed that observing the activity of a few tens of ‘A’ neurons permits to infer the stimulus onset latency with a temporal precision sufficient to recover nearly 95% of the total stimulus information.
These results demonstrate the existence of a specific population of neurons in auditory cortex which possess the required temporal precision and response reliability to serve as an intrinsic temporal reference signaling the onset of a to-be-decoded sound. In addition, they show that the relative timing between neurons in auditory cortex carries considerable stimulus information, not only when considering information in onset latencies, but also in sustained spike patterns.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Brasselet R{rbrasselet}{Department Physiology of Cognitive Processes}, Panzeri S{stefano}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Poster{ BarbieriMLPB2011,
title = {The dynamics of local field potential in monkey primary visual cortex under naturalistic stimulation is well captured by a model network of excitatory and inhibitory integrate-and-fire neurons},
year = {2011},
month = {11},
volume = {41},
number = {483.02},
abstract = {How sensory stimuli are encoded in neuronal activity is a major challenge for understanding perception. A prominent effect of sensory stimulation is to elicit oscillations in the Local Field Potential (LFP) recordings over a broad range of frequencies. The mechanism underlying the emergence of oscillations and their role in encoding sensory information is still not clear. Recent work suggested the idea that different stimulus features could be encoded in the neural activity at different timescales. Belitski et al. [1] recorded LFPs and spiking activity in the primary visual cortex of anesthetized macaques presented with naturalistic movies and found that the power of the gamma and low-frequency bands of LFP carried largely independent information about visual stimuli, while the information carried by the spiking activity was redundant with that carried by the gamma-band LFPs. To better understand these findings, Mazzoni et al. [2] simulated a sparsely connected network of excitatory and inhibitory neurons modeling a local cortical population. They demonstrated that an increase in external inputs leads both to an increase in spiking activity, and an increase in gamma-range LFP oscillations that are generated by the excitatory-inhibitory interactions, while the low-frequency band of the LFP encodes the dynamics at slow time scales of the input. Furthermore, it was shown that low and high frequencies bands work are essentially independent channels for encoding information, in agreement with the experimental findings [1].
In this work we reconsider the dynamics of a model of excitatory and inhibitory integrate-and-fire neurons in the presence of time-dependent inputs and compute analytically average firing rate and LFP spectra, together with the information that they convey about the stimulus. We used two different type of inputs: (1) stimuli that are constant during temporal intervals of fixed duration, but then change abruptly to a new value from an interval to the next (2) a dynamic stimulus which evolves according to an Ornstein-Uhlenbeck (OU) process. We then used the derived analytical formulas to fit the data recorded in anesthetized monkeys. We first fitted parameters characterizing the network model using spontaneous activity (i.e. before the movie starts). We then fit parameters characterizing the input to the network during the movie. In all cases, we find that the analytical formulas provide excellent fits to the data. This analytical approach can be used to identify the key parameters underlying input-dependent changes in the LFP spectral dynamics.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Barbieri F, Mazzoni A, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Panzeri S{stefano} and Brunel N}
}

@Poster{ LippertTKO2011,
title = {The Rat Parietal Cortex: candidate areas for studying multisensory integration},
year = {2011},
month = {11},
volume = {41},
number = {575.17},
abstract = {Much contemporary work is trying to elucidate how the brain integrates the information provided by the different senses into a coherent percept. To reveal causal contributions of individual areas in this process model systems are required that allow i) simultaneous assessment of neural activity across sensory streams, ii) use of genetic techniques to manipulate neural function, and iii) to perform all this in awake behaving animals. Using a combination of functional imaging and electrophysiology we highlight the rat parietal cortex (region PtA) as one promising candidate area.
We first studied the convergence of visual and somatosensory-evoked responses using high-resolution intrinsic imaging in urethane anaesthetized rats. We found a consistent (n=11) overlap of significant responses to both modalities in an elongated region between the presumed unisensory visual and somatosensory cortices. This region showed properties of an association area and overlapped with region PtA as defined by Paxinos and Watson1. Subsequent to localizing this multisensory region we inserted a multisite electrode at the point of largest co-activation. This confirmed the multisensory nature of this region as both current source densities (CSD) and multi-unit activity (MUA) revealed significant responses to both stimuli. In addition, we directly tested for functional signs of multisensory integration, such as non-additive response interactions23. Intriguingly, we found that the multisensory interaction depends on the temporal sequence of the stimuli: CSD-sinks interacted super-additively when the somatosensory stimulus preceded (21±4% enhancement, mean and s.e.m.), but sub-additively when the visual stimulus preceded (-43±11%). For MUA, both stimulus sequences resulted in sub-additive interactions (-32±9% and -46±16%, respectively). Control experiments revealed no bi-modal responses or non-additive interactions in visual cortex, confirming the specificity of the multisensory response patterns to the parietal association region.
Our results reveal a region in the parietal cortex which features the key criteria of multisensory processing2. Previous studies have shown the ability of rats to combine visual and somatosensory information, and the highlighted area constitutes a promising model to elucidate underlying neural mechanisms.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Lippert MT{mlippert}{Department Physiology of Cognitive Processes}, Takagaki K, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration} and Ohl FW}
}

@Poster{ SchriddeMPL2011,
title = {Amplitude and timing of BOLD fMRI are related to specific LFP frequency bands},
year = {2011},
month = {11},
volume = {41},
number = {398.16},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {accepted},
author = {Schridde U{schridde}{Department Physiology of Cognitive Processes}, Magri C{cmagri}{Department Physiology of Cognitive Processes}, Panzeri S{stefano} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ SchindlerKB2011_2,
title = {Decoding Egocentric Space in human Posterior Parietal Cortex using fMRI},
year = {2011},
month = {10},
volume = {12},
pages = {40},
abstract = {In our subjective experience, there is a tight link between covert visual attention and egocentric
spatial attention. One key difference is that the latter can extend beyond the visual
field, providing us with an acurate mental representation of an object’s location relative to
our body position. A neural link between visual and ego-centric spatial attention is suggested
by lesions in parietal cortex, that lead not only to deficits in covert visual attention, but
frequently also to a disorder of ego-centric spatial awareness, known as hemi-spatial neglect.
While parietal involvement in covert visual spatial attention has been much studied, relatively
little is known about mental representations of the unseen space around. In the present study
we examined whether also unseen spatial locations beyond the visual field are represented
in parietal activity, and how they are related to retinotopic representations. We employed a
novel virtual reality (VR) paradigm during functional magnetic resonance imaging (fMRI),
whereby observers were prompted to draw their spatial attention to the position of one of
eight possible objects located around them in an octagonal room. By changing the observers’
facing direction every few trials, the ego-centric location of objects was disentangled from their
absolute position and from the objectsâ identity. Thus, mental representations of egocentric
space surrounding the observer were sampled eight-fold. Decoding results of a multivariate
pattern analysis classifier (MVPA), but not univariate results, showed that egocentric spatial
directions were specifically represented in parietal cortex. These representations overlapped
only partly with visually driven retinotopic activity. Our results thus show that parietal cortex
codes not only for retinotopic and visually accessible space, but also for ego-centric locations
of the three-dimensional space surrounding us, including unseen space.},
web_url = {http://www.neuroschool-tuebingen-nena.de/index.php?id=284},
event_name = {12th Conference of Junior Neuroscientists of Tübingen (NeNA 2011)},
event_place = {Heiligkreuztal, Germany},
state = {published},
author = {Schindler A{aschindler}{Department Physiology of Cognitive Processes}, Kleiner M{kleinerm}{Department Human Perception, Cognition and Action} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ vanKeulenLE2011,
title = {Differential noradrenergic modulation of the rat somatosensory and prefrontal cortex},
year = {2011},
month = {10},
volume = {12},
pages = {46},
abstract = {Noradrenaline (NE) is known to modulate sensory processing by increasing the signal-tonoise
ratio (SNR). Pre- and postsynaptic mechanisms acting on cortical adrenoreceptors have
been implicated. The noradrenergic nucleus Locus Coeruleus (LC) is activated by sensory
stimulation. However, the contribution of the sensory-evoked discharge in LC to modulation
of cortical sensory responses is not well understood. We compared the effects of systemic
or local (in LC) application of clonidine, an alpha2-receptor agonist, which is known to
inhibit LC-NE neurons, on sensory responses in two cortical targets of LC. Simultaneous
recordings in LC, primary Somatosensory (S1) and medial Prefrontal Cortex (mPFC) were
performed in the urethane-anesthetized rat. Electrical foot shocks (FS) of the contralateral
hind paw served as somatosensory stimuli (0.5ms, 5mA). The LC responses to FS differed
dramatically after local and systemic clonidine administration. Iontophoretic application of
clonidine (50nA, 50μl/ml, 20min) into LC resulted in complete cessation of both spontaneous
and evoked activity of LC-NE neurons. Systemic clonidine (50 μl/ml, i.p.) produced a decrease
in LC firing (less than 50% baseline for 30 min), however the LC responses to FS were
preserved. Both local and systemic clonidine administration increased spontaneous activity
in S1 and mPFC. The evoked responses in S1 were unchanged under condition of complete
inhibition of the ipsilateral LC by local application of clonidine (n=13) and decreased during
systemic clonidine condition (n=13). In mPFC, 8 units (40%) increased and 9 units (45%)
decreased the response amplitude following local inhibition of LC. Four out of 24 mPFC
neurons showed increased responses after systemic clonidine injection. Strikingly, 20% of
initially non-responsive mPFC neurons became responsive (n=7) in case of local inhibition of
LC. The same phenomenon was observed during systemic clonidine in 58% of cases (n=14).
Thus, blocking the LC sensory-evoked discharge differentially affected signal processing in
S1 and mPFC. The responses in S1 were preserved, while responses of a large proportion of
mPFC neurons ( 50%) were affected. We observed the opposite effects in S1 (decrease SNR)
and mPFC (increased signaling) after activation of the alpha2 receptors in the entire brain.
Overall, we conclude that alpha2 receptors are involved in sensory signal processing in both
cortical regions, but mPFC receives a stronger NE neuromodulatory input.},
web_url = {http://www.neuroschool-tuebingen-nena.de/index.php?id=284},
event_name = {12th Conference of Junior Neuroscientists of Tübingen (NeNA 2011)},
event_place = {Heiligkreuztal, Germany},
state = {published},
author = {van Keulen S{svankeulen}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}}
}

@Poster{ BahmaniLK2011,
title = {Neural correlates of binocular rivalry in parietal cortex},
journal = {Frontiers in Computational Neuroscience},
year = {2011},
month = {10},
number = {Conference Abstract: BC11},
abstract = {When dissimilar images are presented to the two eyes, perception starts alternating spontaneously between each monocular view, a phenomenon called binocular rivalry (Leopold and Logothetis, 1999). Several imaging studies in humans have shown the involvement of a frontoparietal network of cortical areas in perceptual transitions during binocular rivalry (Lumer et al., 1998). Here we investigate the possible role of parietal visual areas in perceptual alternations during rivalry in the rhesus macaque. Neural activity in the lateral intraparietal area (LIP) was recorded extracellularly while the subject was presented dichoptically and asynchronously with two rivalrous patterns, resulting in flash suppression (Keliris et al., 2010). The paradigm ensures excellent control over the subject’s perceptual state.
Preliminary results confirm the transient change of brain activity around perceptual reversals at the single cell level. The recorded cells typically showed an initial burst of activity after the onset of a stimulus as well as at stimulus/perceptual changes, followed by a sustained response (Bisley, 2004). The transient response of recorded neurons has a short latency, lasts a few hundred milliseconds and is always positive while the sustained response is suppressive in some cells and excitatory in others. We speculate that these responses may reflect two separate underlying processes. The short latency response may reflect a fast sensory signal conveying the information in a bottom-up manner, while the sustained activity may represent top-down influences originating from higher areas in the prefrontal cortex. The functional magnetic resonance imaging (fMRI) studies performed previously could not dissociate these two tightly overlapping signals because of the poor temporal resolution of the technique.

Analysis of the firing rates of single and multi-units indicate that the transient part of the response predicts well the change in perception while the sustained activity does not show a significant correlation with perceptual state. This might be explained by the little selectivity of the sustained response of parietal neurons towards particular stimuli (Lehky and Sereno, 2007). It is believed that LIP neurons provide a representational map of saliency, integrating bottom-up and top-down information to guide the allocation of spatial attention (Bisley et al., 2011). We argue that the transient response of LIP neurons after perceptual switches is an indication for a role of this region in providing a change signal to higher areas. It is possible, that the intraparietal activation observed in humans around perceptual transitions may simply reflect the elevation of neural activity as a result of a novel percept rather than a causal role of the region in driving the switches. We are therefore planning to extend the binocular flash suppression paradigm to normal binocular rivalry and monitor the activity around spontaneous perceptual alternations in order to delineate what happens without any concomitant physical change in the stimulus.
Furthermore, local field potentials, temporal dynamics of single unit activity and synchronization between neurons might provide a better understanding of the top-down influences of prefrontal cortex especially during the sustained response. This analysis is currently in progress.},
web_url = {http://www.bccn-2011.uni-freiburg.de/proceedings.pdf},
event_name = {Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting  (BC11)},
event_place = {Freiburg, Germany},
state = {published},
DOI = {10.3389/conf.fncom.2011.53.00134},
author = {Bahmani H{hbahmani}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Keliris GA{george}{Department Physiology of Cognitive Processes}}
}

@Poster{ BahmaniLK2011_2,
title = {Neural Correlates of Binocular Rivalry in Parietal Cortex},
year = {2011},
month = {10},
volume = {12},
pages = {22},
abstract = {When dissimilar images are presented to the two eyes, perception starts alternating spontaneously
between each monocular view, a phenomenon called binocular rivalry (Leopold and
Logothetis, 1999). Several imaging studies in humans have shown the involvement of a frontoparietal
network of cortical areas in perceptual transitions during binocular rivalry (Lumer
et al., 1998). Here we investigate the possible role of parietal visual areas in perceptual alternations
during rivalry in the rhesus macaque. Neural activity in the lateral intraparietal area
(LIP) was recorded extracellularly while the subject was presented dichoptically and asynchronously
with two rivalrous patterns, resulting in flash suppression (Keliris et al., 2010).
The paradigm ensures excellent control over the subjectâs perceptual state. Preliminary results
confirm the transient change of brain activity around perceptual reversals at the single
cell level. The recorded cells typically showed an initial burst of activity after the onset of a
stimulus as well as at stimulus/perceptual changes, followed by a sustained response (Bisley,
2004). The transient response of recorded neurons has a short latency, lasts a few hundred
milliseconds and is always positive while the sustained response is suppressive in some cells
and excitatory in others. We speculate that these responses may reflect two separate underlying
processes. The short latency response may reflect a fast sensory signal conveying
the information in a bottom-up manner, while the sustained activity may represent top-down
influences originating from higher areas in the prefrontal cortex. The functional magnetic resonance
imaging (fMRI) studies performed previously could not dissociate these two tightly
overlapping signals because of the poor temporal resolution of the technique. Analysis of the
firing rates of single and multi-units indicate that the transient part of the response predicts
well the change in perception while the sustained activity does not show a significant correlation
with perceptual state. This might be explained by the little selectivity of the sustained
response of parietal neurons towards particular stimuli (Lehky and Sereno, 2007). It is believed
that LIP neurons provide a representational map of saliency, integrating bottom-up
and top-down information to guide the allocation of spatial attention (Bisley et al., 2011). We
argue that the transient response of LIP neurons after perceptual switches is an indication
for a role of this region in providing a change signal to higher areas. It is possible, that the
intraparietal activation observed in humans around perceptual transitions may simply reflect
the elevation of neural activity as a result of a novel percept rather than a causal role of the
region in driving the switches. We are therefore planning to extend the binocular flash suppression
paradigm to normal binocular rivalry and monitor the activity around spontaneous
perceptual alternations in order to delineate what happens without any concomitant physical
change in the stimulus. Furthermore, local field potentials, temporal dynamics of single
unit activity and synchronization between neurons might provide a better understanding of
the top-down influences of prefrontal cortex especially during the sustained response. This
analysis is currently in progress.},
web_url = {http://www.neuroschool-tuebingen-nena.de/index.php?id=284},
event_name = {12th Conference of Junior Neuroscientists of Tübingen (NeNA 2011)},
event_place = {Heiligkreuztal, Germany},
state = {published},
author = {Bahmani H{hbahmani}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Keliris GA{george}{Department Physiology of Cognitive Processes}}
}

@Poster{ BrasseletPLK2011_2,
title = {Neurons with unselective rapid responses as reference for relative temporal coding in primate auditory cortex},
journal = {Frontiers in Computational Neuroscience},
year = {2011},
month = {10},
volume = {Conference Abstract: BC11},
abstract = {Vocalizations or speech constitute dynamic inputs that are represented in auditory cortices by precise time-varying activity patterns. Such response patterns are typically analyzed by aligning spikes and sensory events using the experimenter’s clock, a laboratory-based reference not available to the brain. In contrast, neural systems must interpret time-varying responses using only intrinsic reference frames, a particularly challenging task for stimuli appearing suddenly or unpredictably. One solution could be provided by encoding information in the relative timing of neural responses, thereby exploiting intrinsic temporal reference frames. But it remains unclear whether and how sensory cortices implement a neural reference suitable for relative coding schemes. We investigate the viability of such a relative coding scheme in primate auditory cortex using a paradigm where naturalistic sounds were presented at random (unexpected) times. Recording neural responses in macaque auditory cortex we found that neurons clustered in two subsets with different properties. A set of stereotypical neurons responded rapidly and unselectively to individual stimuli with minimally varying latency, while another set of stimulus-selective neurons responded slowly and selectively with high latency variability. We then tested the hypothesis that the latency of the stereotypical neurons can provide a reliable and intrinsic reference frame for relative coding schemes. Specifically, we calculated the stimulus information carried by the selective neurons in different neural codes based on the relative timing of their neural responses to either a stereotypical neuron or another selective neuron. Two codes were considered: the relative onset latency between neurons and the full spike train of the selective neuron aligned to the response onset of a reference neuron. Information in latency relative to stereotypical neurons reached 91% of the information in latency with respect to the stimulus onset. The spike trains of the selective neurons relative to the stereotypical neurons contains 84% of the information in spike trains aligned to the stimulus onset, but only 41% relative to another selective neuron. At the population level, an estimate of the latency based on 20 stereotypical neurons allows preserving 95% of the information as measured with the experimenter's clock. We thus demonstrate that information in response latencies and sustained time-varying responses may be decoded by measuring these relative to another neuron’s or a population response. Stereotypical neurons responding unselectively and rapidly to various complex stimuli may serve as an early saliency signal that provides a reliable temporal reference frame that can be used to extract information in the responses of more selective neurons.},
web_url = {http://www.frontiersin.org/10.3389/conf.fncom.2011.53.00086/1484/bernstein_conference_2011/all_events/event_abstract},
event_name = {Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting (BC11)},
event_place = {Freiburg, Germany},
state = {published},
DOI = {10.3389/conf.fncom.2011.53.00086},
author = {Brasselet R{rbrasselet}{Department Physiology of Cognitive Processes}, Panzeri S{stefano}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Poster{ ZaretskayaAB2011,
title = {Parietal cortex mediates perceptual grouping of local elements into a whole},
year = {2011},
month = {10},
volume = {12},
pages = {53},
abstract = {Grouping local elements into a holistic percept, also known as spatial binding, is crucial for
meaningful perception. Lesions in posterior parts of the brain are known to impair perceptual
grouping, but in the healthy brain this process has only been studied indirectly. Here we use
a novel bi-stable illusion, which induces alternating and mutually exclusive subjective experiences
of either grouped (global) or ungrouped (local) elements, while the visual stimulation
remains the same. We show that global perceptual periods are related to stronger brain activity
in the parietal cortex and that they are selectively shortened when parietal activity is
disturbed by brain stimulation. Our findings thus provide direct evidence that consciously
experienced grouping is mediated by parietal function, similar to attention and perceptual
selection.},
web_url = {http://www.neuroschool-tuebingen-nena.de/index.php?id=284},
event_name = {12th Conference of Junior Neuroscientists of Tübingen (NeNA 2011)},
event_place = {Heiligkreuztal, Germany},
state = {published},
author = {Zaretskaya N{nataliya}{Department Physiology of Cognitive Processes}{Department High-Field Magnetic Resonance}, Anstis S and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ PapanikolaouKSKSLS2011,
title = {Population receptive field mapping in human subjects with visual cortical lesions},
year = {2011},
month = {10},
volume = {12},
pages = {37},
abstract = {Damage to the primary visual cortex (V1) as a result of stroke typically leads to the inability
to perceive visual stimuli in the affected region of the contralateral visual hemifield (scotoma).
However, in spite of this, several higher visual areas have been shown to be modulated by
visual stimuli presented inside the scotoma. A much debated issue is whether adult visual
cortex is able to reorganize after injury, and if so, what is the extent and the mechanism of the
observed reorganization. We use functional magnetic resonance imaging (fMRI) methods to
study visual cortex reorganization after injury in adult human subjects.To this end we applied
a method introduced by Dumoulin and Wandell (Dumoulin SO, Wandell BA, Population receptive
field estimates in human visual cortex, Neuroimage 39, 2008), which uses functional
magnetic resonance imaging (fMRI) to measure the aggregate receptive field properties of
neuronal populations voxel by voxel in the visual cortex. FMRI measurements were obtained
during the presentation of a moving bar stimulus which traversed the visual field while the
subjects were fixating and these measurements were used to derive an estimate of the voxel
based population receptive field center and radius. We studied several subjects with quadrandanopsia
and hemianopsia resulting from cortical lesions and compared them to the range of
measurements obtained from a group of normal controls. In general, retinotopic maps in the
patients’ spared early visual cortex appear to be consistent with retinotopic maps obtained
in control. subjects. The organization of higher level visual areas, such as V3a/b and MT
show preliminary some differences compared to those of normal subjects. Also preliminary
results on the population receptive field size of some of the patients’ spared visual areas show
deviations from the normal range of population receptive field sizes derived from the control
subjects. We are in the process of obtaining further measurements to confirm these findings
and to assess to what degree they correspond to cortical reorganization.},
web_url = {http://www.neuroschool-tuebingen-nena.de/index.php?id=284},
event_name = {12th Conference of Junior Neuroscientists of Tübingen (NeNA 2011)},
event_place = {Heiligkreuztal, Germany},
state = {published},
author = {Papanikolaou A{amalia}{Department Physiology of Cognitive Processes}, Keliris G{george}{Department Physiology of Cognitive Processes}, Shao Y{yshao}{Department Physiology of Cognitive Processes}, Krapp E, Schiefer U, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Smirnakis S}
}

@Poster{ VeitBKR2011,
title = {Receptive field properties of tree shrew primary visual neurons and local field potentials},
year = {2011},
month = {10},
volume = {12},
pages = {48},
abstract = {The local field potential (LFP) comprises the low frequency membrane potential fluctuations
of an extracellular recording. It is thought to be closely related to frequently used, noninvasively
recorded signals such as the EEG or the BOLD signal and has been proven to show
some stimulus selectivity in various brain regions. Thus the relationship of the LFP to the
spiking activity as well as a comparison of their level of selectivity is of great interest. We
simultaneously recorded spiking activity and LFPs from tree shrew primary visual cortex
using pairs or triplets of tetrodes separated by between 200 and 1200μm. We map the receptive
fields at eccentricities between 10 and 25deg using binary sparse noise and estimate
their spatial extent by fitting oriented two dimensional Gaussians to the resulting activation
map. We have preliminary data from 49 pairs of simultaneously recorded neurons as well as
18 additional single sites from a total of 14 animals. The visual spread of the receptive field
estimated from the trial averaged LFP ( 2.99deg2) was statistically similar to the one for the
spiking activity ( 3.06deg2). Estimating the receptive field size using LFP gamma power (30-
90Hz), we found significantly smaller values ( 2.17deg2) compared to the above two conditions
(1-way ANOVA: p«0.001). In addition, we found that receptive fields tended to be ellipsoidal:
long to short axis ratio: 1.41 (LFP) and 1.36 (spikes) and oriented mostly horizontally: mean
angle 5.79deg (LFP) and 6.95deg (spikes). This bias toward horizontal orientations was statistically
significant (Rayleigh tests: p « 0.001) for both signal types. Relating the spatial
separation between the tetrodes to the respective receptive field centers, we found that 1deg
of visual angle corresponded to a cortical distance of around 180μm for both spikes and LFP.
Our results suggest that the spatial extent of activation estimated from LFPs can be similar
or smaller than the values for spiking activity depending on which features of the LFP
are analyzed. Thus, we obtained smaller receptive field sizes using gamma-band oscillations
compared to trial-averaged stimulus evoked LFPs. Our findings represent the first detailed
investigations of this relationship in tree shrew V1, and are in good general agreement with
related work in macaque monkeys.},
web_url = {http://www.neuroschool-tuebingen-nena.de/index.php?id=284},
event_name = {12th Conference of Junior Neuroscientists of Tübingen (NeNA 2011)},
event_place = {Heiligkreuztal, Germany},
state = {published},
author = {Veit J{jveit}{Department Physiology of Cognitive Processes}, Bhattacharyya A{anwesha}{Department Physiology of Cognitive Processes}, Kretz R and Rainer G{gregor}}
}

@Poster{ LangeCanhosMLE2011,
title = {The role of noradrenergic modulation for auditory discrimination learning in rats: development of a behavioral paradigm},
year = {2011},
month = {10},
volume = {12},
pages = {31-32},
abstract = {The brain noradrenergic (NA) system is of great importance for animal vital activities as it
modulates a variety of cognitive processes, such as vigilance, arousal, attention, memory and
learning (Berridge & Waterhouse, 2003). Earlier studies showed a relation between NA systems
activity and attention. For example, pharmacological activation of the NA system with
2-adrenergic receptor antagonist (idazoxan) resulted in improved performance in cognitive
tasks involving exploration of novel stimuli (Devauges & Sara, 1990). In contrast, 2-agonist
(clonidine) administration led to increase of the reaction time in a visuospatial target detection
task (Mair et al. 2005). We aim to investigate the effects of NA on performance of an
auditory discrimination task in rats. To manipulate the activity of NA system we will apply
electrical stimulation of the Locus Coeruleus (LC), a small brainstem nucleus that contains
the majority of brain NA neurons. This nucleus presents a very widespread net of efferent
projections in the central nervous system and its activation leads to facilitation of sensoryevoked
neuronal firing in different brain regions involved in information processing, including
sensory cortices and thalamus. In all of these structures, the NA systemâs neurotransmitter
norepinephrine (NE) optimizes neuronal signaling by increasing the signal-to-noise ratio
of the neuronal responses and enhancing the response selectivity. The LC neurons display
two types of activity: tonic and phasic discharges, depending on the behavioral state. The
tonic discharge defines the general arousal state and phasic discharges are closely linked to
processing of salient stimuli and focused attention, e.g. attendance to novel stimuli or target
detection (Aston-Jones et al. 1997). In our experiments, we will use the LC stimulation parameters
to mimic natural phasic discharges of the LC neurons and phasically activate LC
at presentation of auditory stimuli. First, we developed a behavioral paradigm for auditory
discrimination task in a fully-automated operant box. The task consisted in the discrimination
of two sounds of distinct frequencies, 4 and 10 kHz. The rats had to initiate the sound
presentation by nose-poking to an aperture in the center of the box wall. Each sound was
associated with the reward (chocolate milk) delivery on the right or left port located on the
opposite side of the box. The sounds were presented in a pseudo-random order. In case of
incorrect choice, the trial was terminated and the rat had to initiate the next sound presentation.
In order to achieve a reliable above-chance performance, the rats were trained using
a multiple-step conditioning paradigm, which gradually led to the final performance of the
discrimination task: (1) habituation - familiarization with the box and substance of reward;
(2) sound-reward association â each sound presentation was paired with reward (3) reward
delivery only when nose-poking during sound presentation (4) introduction of the trial initiation
by nose-poking; and (5) introduction of the auditory discrimination task with repetition
of the same sound in case of incorrect choice. The latter step was crucial for the effective
discrimination learning as it prevented the rats from using a place preference strategy and
forced them to pay attention to the properties of the sounds presented instead of responding
randomly and inattentively and performing at a 50% success rate. Using this paradigm the
rats needed 10-15 daily training sessions for steps 1-4; and 30 additional sessions to achieve a
stable performance at 70% accuracy (step 5 and the full task). All the rats trained with this paradigm (n=6) achieved the above-chance performance and were qualified for implantation
of the chronic stimulation electrode into LC. All rats were able to perform the task with the
same accuracy when tested 1 week after surgery. The majority of rats continued performing
satisfactorily after the cable plugging procedure to the electrode socket on the rat head was
introduced. Thus, the implemented behavioral paradigm results in a stable discrimination
learning that was resistant to such manipulations as anesthesia during surgery, 1 week postsurgery
recovery period, and the cable plugging procedure. We are currently collecting data
on the effects of electrical stimulation of LC on performance of auditory discrimination task
in the trained rats. The stimulation parameters are based on results obtained in our laboratory
in anesthetized animals, which induce a transient desynchronization of the local field
potentials in the prefrontal cortex. We will stimulate LC with 500ms trains of pulses (0.4
ms, 50 μA, 50Hz) delivered immediately after trial initiation. We expect that such phasic
activation of LC will increase NE release in the target cortical regions involved in the sensory
discrimination and decision making and therefore affect the behavioral performance.},
web_url = {http://www.neuroschool-tuebingen-nena.de/index.php?id=284},
event_name = {12th Conference of Junior Neuroscientists of Tübingen (NeNA 2011)},
event_place = {Heiligkreuztal, Germany},
state = {published},
author = {Lange Canhos L{lcanhos}{Department Physiology of Cognitive Processes}, Marzo A{amarzo}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}}
}

@Poster{ PerezIMCHGALMP2011,
title = {Brain hemispheric structural efficiency and interconnectivity rightward asymmetry},
journal = {Frontiers in Human Neuroscience},
year = {2011},
month = {9},
volume = {Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI)},
abstract = {To estimate white matter interregional axonal pathways and to infer left and right common anatomical network properties, obtaining global and local measures that allow us to evaluate structural network (dis)similarities between hemispheres, high-angular resolution DW-MRI datasets were acquired in 11 right-handed healthy subjects. T2-weighted images were parcellated into 90 gray matter structures. 3 axonal connectivity values were estimated using 3 fiber tractography algorithms: FSL, PICo, and a graph-based tractography algorithm. Whole-brain network was segmented into left and right hemispheric networks and analyzed in a graph framework: anatomic regions representing nodes and connections obtained from tractography representing arcs. Topological parameters of global efficiency, local efficiency, interconnectivity and betweenness centrality were extracted. Lateralization index was computed for these measures. We found significant differences between right and left hemispheric networks at a hemispheric level for the efficiency and interconnectivity metrics. Also, 21 pairs of human homolog regions were found lateralized according to centrality (15 leftward & 6 rightward). These indicate either that the right hemisphere is, at the whole-hemisphere level, more efficient and interconnected and also that the left hemisphere presents more central or indispensable regions for the whole-brain structural network. A greater left hemisphere functional specialization could lead to its apparently ‘worse’ general structural organization. Results are in line with the fact that the left hemisphere has a leading role for highly demanding specific process (e.g.language and motor actions), whereas the right hemisphere has a leading role for more general process (e.g.integration tasks).},
web_url = {http://www.frontiersin.org/10.3389/conf.fnhum.2011.207.00181/event_abstract},
event_name = {XI International Conference on Cognitive Neuroscience (ICON XI)},
event_place = {Palma, Mallorca, Spain},
state = {published},
DOI = {10.3389/conf.fnhum.2011.207.00181},
author = {P{\'e}rez A, Iturria-Medina Y, Morris D, Canales-Rodr{\'i}guez E, Haroon H, Garc{\'i}a l, Augath M{mark}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Melie-Garcia L and Parker G}
}

@Poster{ MagriSPML2011,
title = {Different LFP frequency bands convey complementary information about the BOLD signal},
journal = {BMC Neuroscience},
year = {2011},
month = {7},
volume = {12},
number = {Suppl 1},
pages = {P204},
abstract = {Blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is the most widely used noninvasive imaging technique for investigating brain activity. However, the BOLD signal is only indirectly coupled to the underlying neural activity and the relationship between the two signals is not fully understood [1]. Recordings in anaesthetized and awake monkeys have shown that hemodynamic responses are strongly related to local field potentials (LFPs) [2,3]. LFPs are thought to represent the input and intracortical processing in a cortical area and are usually separated into different frequency bands that reflect different neural processes [4]. Previous studies have shown that different LFP bands correlate differently with the BOLD signal [3,5,6]. However little is known about which property of the BOLD signal is reflected by each band and whether different bands convey different information about the BOLD signal. To address this question we performed simultaneous recordings of neural activity and BOLD fMRI in early visual areas V1 and V2 in 4 anesthetized monkeys. All measurements were performed with the monkeys sitting in complete darkness while no stimulus was being presented. We computed mutual information between LFP power and BOLD fMRI to determine which frequencies in the LFPs were most informative about the BOLD signal. We found three highly informative bands, namely the alpha band [8-12Hz], the gamma band [40-100Hz] and the [18-35 Hz] “nMod” band that was previously found to be unrelated to visual stimuli and was thus suggested to primarily reflect neuromodulatory input [4]. We found that gamma power was the most informative about BOLD fMRI and reflected well changes in the amplitude of the BOLD signal. In particular, an increase in gamma power above its median value was followed, on average, by an increase in BOLD signal, and the BOLD signal decreased, instead, following a decrease in gamma power below its median. Moreover, we found that gamma and nMod power were complementary, i.e. that by combining nMod power together with gamma power we could extract 30% more information than could be extracted from gamma power alone. We investigated the origin of this complementarity and we found that the power in the nMod band reflected the timing with which changes in BOLD signal occurred following changes in gamma power. Finally, we found that, as suggested by previous theoretical work [7], an increase in alpha power without a change in total LFP power was followed by a decrease in BOLD signal and vice versa. These results indicate that distinct neural processes are reflected differently in the BOLD signal and that, consequently, it may be possible to retrieve information about the different contributions from the recorded BOLD time course.},
web_url = {http://www.biomedcentral.com/content/pdf/1471-2202-12-S1-P204.pdf},
event_name = {Twentieth Annual Computational Neuroscience Meeting (CNS*2011)},
event_place = {Stockholm, Sweden},
state = {published},
DOI = {10.1186/1471-2202-12-S1-P204},
author = {Magri C{cmagri}{Department Physiology of Cognitive Processes}, Schridde U{schridde}{Department Physiology of Cognitive Processes}, Panzeri S{stefano}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ SiadatnejadPKLM2011,
title = {Does the information in the phase of low frequency LFP reflect the low frequency envelope of local spike rates?},
journal = {BMC Neuroscience},
year = {2011},
month = {7},
volume = {12},
number = {Suppl 1},
pages = {P227},
abstract = {Recently, it has been shown that when the timing of spikes is measured relative to the phase of the cortical local field potentials (LFP), spikes can carry substantial more information about an external stimulus [1]. Experimental studies in sensory cortices of macaque have shown that the extra information obtained with such phase-of-firing codes above that in the firing rate alone ranges from 55% in primary visual cortex [1] to more than 100% in primary auditory cortex [2]. Here, we use a mathematical model that relates local spike trains and the resulting LFP, to explain the emergence of the phase-of-firing codes in cortex. The model is based on the one proposed in [3] and incorporates two types of integration over the spiking activity: i) a time convolution that results from the filtering properties of neural structures [4], which embeds history effects in LFP from past spiking activity, and ii) an integration step over the activity of neurons in the neighbourhood of the measuring electrode.

When the spikes recorded from macaque primary visual cortex were used to synthesize the LFP, the model could reproduce the phase-of-firing information found using the real LFP, as shown in Figure 1. This suggests that an important component of phase-of-firing information originates from the surrounding neural population and past spiking activity. The next question that arises is what is the relative contribution of the neuron population size and the length of the firing rate history embedded in the LFP. We are currently investigating this question by parametrically varying both the population size and time integration ranges in generating the synthetic LFP.},
web_url = {http://www.biomedcentral.com/1471-2202/12/S1/P227},
event_name = {Twentieth Annual Computational Neuroscience Meeting (CNS*2011)},
event_place = {Stockholm, Sweden},
state = {published},
DOI = {10.1186/1471-2202-12-S1-P227},
author = {Siadatnejad S, Panzeri S{stefano}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Montemurro MA}
}

@Poster{ MazzoniKMMQLP2011,
title = {Local field potential phase and spike timing convey information about different visual features in primary visual cortex},
journal = {BMC Neuroscience},
year = {2011},
month = {7},
volume = {12},
number = {Suppl 1},
pages = {P248},
abstract = {The natural visual environment is characterized by both “what/where” aspects (image features such as contrast or orientation which are defined by the relationship between visual signals simultaneously presented at different points in space) and “when” aspects, describing the temporal variations of the image features. Both “when” and “what/where” information is necessary to describe and understand the natural visual environment, and to take appropriate behavioral decisions. While “where” can be considered embedded as retinotopy, it is likely that localized neural populations in the visual cortex keep a simultaneous representation of both “what” and “when” aspects of the visual stimuli. However, little is yet known about how the spike trains of neurons in primary visual cortex encode both sources of information.

The traditional hypothesis in systems neuroscience is that sensory variables are represented by a rate code, i.e. all sensory information is encoded by the number of spikes emitted over relatively long time windows. Although the relevance of rate in encoding static features is well established, this code can be inherently ambiguous in changing environments [1] and it is unlikely that this code is rich enough to represent simultaneously different types of information. Therefore here we explore the hypothesis that the timing of spikes is a crucial variable in representing both “what” and “when” aspects of the natural visual environment.

To address these issues, we recorded single unit activity and LFPs in primary visual cortex of opiate anaesthetized macaques during the binocular presentation of naturalistic color movies. By means of computational analysis, we extracted several image features (color, orientation, luminance, space and time contrast, motion) from the receptive fields of each single neuron. We then considered two different spike timing codes previously studied in both the auditory [2] and the visual cortex [3]. In the first code, which we call spike patterns code, sequences of spike times from single neurons are measured (with a resolution of the order of 10 ms) with respect to the time course of the external stimulus. In the second code, which we call phase of firing code, spikes are measured with respect to the phase of the concurrent low frequency LFPs recorded from the same electrode as the spikes. We then used these data to investigate systematically which types of neural codes carry information about the static features of the image and which neural codes carry information about the time course of these features. We found that both “when” and “what” aspects are encoded simultaneously by spike times of visual cortical neurons. However, “what” and “when” are encoded by two different neural information streams; “what” aspects are encoded (on a fine scale of few ms) by spike patterns, and “when” stimulus aspects are encoded by the phase of firing (on a coarse scale of hundreds of ms).},
web_url = {http://www.biomedcentral.com/1471-2202/12/S1/P248},
event_name = {Twentieth Annual Computational Neuroscience Meeting (CNS*2011)},
event_place = {Stockholm, Sweden},
state = {published},
DOI = {10.1186/1471-2202-12-S1-P248},
author = {Mazzoni A, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Martinez J, Quiroga RQ, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Poster{ GoenseL2011,
title = {Differences in neurovascular coupling in areas with positive and negative BOLD signal},
year = {2011},
month = {5},
volume = {19},
number = {3600},
file_url = {fileadmin/user_upload/files/publications/2011/ISMRM-2011-3600.pdf},
web_url = {http://www.ismrm.org/11/index.htm},
event_name = {19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011)},
event_place = {Montréal, Canada},
state = {published},
author = {Goense J{jozien}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ BohrausLG2011,
title = {High resolution CMRO2 in visual cortex of macaca mulatta},
year = {2011},
month = {5},
volume = {19},
number = {3599},
file_url = {fileadmin/user_upload/files/publications/2011/ISMRM-2011-3599.pdf},
web_url = {http://www.ismrm.org/11/index.htm},
event_name = {19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011)},
event_place = {Montréal, Canada},
state = {published},
author = {Bohraus Y{ybohraus}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Goense J{jozien}{Department Physiology of Cognitive Processes}}
}

@Poster{ ValverdeSalzmannLP2011,
title = {High-Resolution Imaging of Vessels in the Isolated Rat Brain},
year = {2011},
month = {5},
volume = {19},
number = {2382},
abstract = {While several atlases are available depicting the spatial distribution of various parameters either measured with MRI or from histological section, no comparable comprehensive data exists for the distribution of vessels in the rat brain. Angiography is able to use the blood flow in the brain of the living rat to display the largest arteries, while SWI can visualize veins down to medium size. The aim of this study was to obtain a full picture of vessels even down to relatively small size in the isolated rat brain perfused
with contrast agents at ultra-high field.},
file_url = {fileadmin/user_upload/files/publications/ISMRM-2011-2382.pdf},
web_url = {http://www.ismrm.org/11/},
event_name = {19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011)},
event_place = {Montréal, Canada},
state = {published},
author = {Valverde Salzmann MF{valverde}{Department High-Field Magnetic Resonance}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Pohmann R{rolf}{Department High-Field Magnetic Resonance}}
}

@Poster{ LiebeHLR2011,
title = {Long range coupling in theta between V4 and prefrontal cortex predicts visual memory performance},
year = {2011},
month = {2},
number = {III-12},
abstract = {Short-term memory entails the encoding, maintenance and subsequent retrieval of sensory information and requires the communication between multiple brain regions mediating these processes. However, whether and how distant cortical areas cooperate during memory tasks is still an open question. In this study we investigate the neural interaction between visual area V4 and the lateral prefrontal cortex (lPF) using paired recordings of local field potentials (LFP) and single unit activity (SUA) in monkeys performing a visual short-term memory task (delayed - match to sample). During the memory period of the task we observed enhanced oscillatory phase - locking of LFPs between both areas that predominantly occurred in the theta frequency band (3-9Hz). In addition, we found that increased theta phase locking at the mesoscopic level of LFPs was associated with stronger phase locking of SUA to theta oscillations of the respective other region. We also assessed the functional significance of increased theta-phase locking by comparing oscillatory synchrony between V4 and lPF LFP-pairs and spike-LFP pairs for trials in which animals correctly identified the stimulus as opposed to when they failed to do so. We observed that the strength of the inter-cortical phase locking was higher for correct than incorrect trials and correlated well with session-to-session variations in monkeysí task performance. Our findings suggest that theta based oscillatory synchrony between V4 and lPF cortex likely provides a basis for the timely coordination of spiking output of V4 and prefrontal neurons during visual short-term memory. The observed correlation between inter-cortical phase locking and memory performance may reflect facilitated communication of visual information during visual memory.},
web_url = {http://www.cosyne.org/c/index.php?title=Cosyne_11_posters3},
event_name = {Computational and Systems Neuroscience Meeting (COSYNE 2011)},
event_place = {Salt Lake City, UT, USA},
state = {published},
author = {Liebe S{sliebe}{Department Physiology of Cognitive Processes}, Hoerzer G, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ BerensEGTB2011_2,
title = {Optimal Population Coding, Revisited},
year = {2011},
month = {2},
number = {III-67},
abstract = {Cortical circuits perform computations within few dozens of milliseconds with each neuron emitting only a few spikes. In this regime conclusions based on Fisher information, which is commonly used to assess the quality of population codes, are not always valid. Here we revisit the effect of tuning function width and correlation structure on neural population codes for angular variables using ideal observer analysis in both reconstruction and classification tasks employing Monte-Carlo simulations and analytical derivations. We show that the optimal tuning width of individual neurons and the optimal correlation structure of the population depend on the signal-to-noise ratio for both the reconstruction and the classification task. Strikingly, both ideal observers lead to very similar conclusions at low signal-to-noise ratio. In contrast, Fisher information favors severely suboptimal coding schemes in this regime. To further investigate the coding properties of Fisher-optimal codes, we compute the full neurometric functions of an ideal observer in the stimulus discrimination task, which allows us to evaluate population codes separately for fine and coarse discrimination. We find that codes with Fisher-optimal tuning width show strikingly bad performance for simple coarse discrimination tasks with a ëpedestal errorí, which is independent of population size. We show analytically that this is a necessary consequence of the fact that in such codes only few neurons are activated by each stimulus, irrespective of the population size. Further we show that the initial region of the neurometric function goes to zero with increasing population size. As a consequence, the overall error achieved by Fisher-optimal ensembles saturates for large populations. In summary, based on exact ideal observer analysis for both stimulus reconstruction and discrimination tasks we obtained (1) an accurate assessment of neural population codes at all signal-to-noise ratios and (2) analytical insights into the suboptimal behavior of Fisher-optimal population codes.},
web_url = {http://www.cosyne.org/c/index.php?title=Cosyne_11_posters3},
event_name = {Computational and Systems Neuroscience Meeting (COSYNE 2011)},
event_place = {Salt Lake City, UT, USA},
state = {published},
author = {Berens P{berens}{Research Group Computational Vision and Neuroscience}, Ecker AS{aecker}{Research Group Computational Vision and Neuroscience}, Gerwinn S{sgerwinn}{Department Empirical Inference}{Research Group Computational Vision and Neuroscience}, Tolias AS{atolias}{Department Physiology of Cognitive Processes} and Bethge M{mbethge}{Research Group Computational Vision and Neuroscience}}
}

@Thesis{ Franke2011,
title = {Real-Time Analysis of Extracellular Multielectrode Recordings},
year = {2011},
month = {12},
state = {published},
type = {PhD},
author = {Franke F{ffranke}{Department Physiology of Cognitive Processes}}
}

@Thesis{ Venkatesh2011,
title = {Analysis of EEG Signals from non-human primates: An Information Theoretic Approach},
year = {2011},
month = {6},
state = {published},
type = {Master},
author = {Venkatesh V{vvenkatesh}{Department Physiology of Cognitive Processes}}
}

@Thesis{ Crocker2011,
title = {An information-theoretic analysis of neural signals in macaque ventrolateral prefrontal cortex},
year = {2011},
month = {5},
state = {published},
type = {Master},
author = {Crocker B{bcrocker}{Department Physiology of Cognitive Processes}}
}

@Miscellaneous{ Schuz2011_3,
title = {Ein Mensch, der auf viele eine große Faszination ausübte: Nachruf für Valentin Braitenberg},
journal = {Campus intern},
year = {2011},
month = {12},
volume = {2011},
number = {Dezember},
pages = {6},
file_url = {fileadmin/user_upload/files/publications/2011/Nachruf_MPI_Campus_Tuebingen_Newsletter_2011.pdf},
state = {published},
author = {Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}}
}

@Miscellaneous{ SchuzA2011,
title = {In memory of Valentin Braitenberg},
journal = {Bernstein Newsletter},
year = {2011},
month = {12},
volume = {2011},
number = {12},
pages = {20-21},
file_url = {fileadmin/user_upload/files/publications/2011/Bernstein_Newsletter_Cover_Text.pdf},
state = {published},
author = {Aertsen A and Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}}
}

@Conference{ Angelovski2011,
title = {Development of dynamic and target-specific MRI probes for neuroimaging},
year = {2011},
month = {11},
web_url = {http://www.e-smi.eu/index.php?id=2024&tx_ttnews[tt_news]=1663&tx_ttnews[backPid]=1996&cHash=48bb25e2e12657c057314b0bc387b2b3},
event_name = {Symposium on MRI Probes for Molecular Imaging: From Design to Application},
event_place = {Tübingen, Germany},
state = {published},
author = {Angelovski G{goran}{Department Physiology of Cognitive Processes}}
}

@Conference{ Engelmann2011,
title = {Towards targeted MRI probes for in vivo applications},
year = {2011},
month = {11},
web_url = {http://www.e-smi.eu/index.php?id=2024&tx_ttnews[tt_news]=1663&tx_ttnews[backPid]=1996&cHash=48bb25e2e12657c057314b0bc387b2b3},
event_name = {Symposium on MRI Probes for Molecular Imaging: From Design to Application},
event_place = {Tübingen, Germany},
state = {published},
author = {Engelmann J{joern}}
}

@Conference{ Kayser2011,
title = {How sounds shape visual processing: acoustic modulation of primary and higher visual cortices},
year = {2011},
month = {10},
number = {135},
abstract = {Current understanding posits that the different senses interact on multiple stages of processing. We investigated this notion using a combination of high-resolution fMRI and electrophysiological recordings in non-human primates. In particular we study how acoustic stimulation affects neural responses in low-level (areas V1 and V2) and higher-tier visual areas (area TE).
In primary visual cortex we find that the presentation of sounds reduces the fMRI-BOLD signal to values below pre-stimulus baseline, but enhances evoked response to visual stimuli above the level attained by pure visual stimulation. This finding is well consistent with previous results in humans, and suggests a modulatory and gain changing mechanism of acoustic stimuli on visual cortex. Noteworthy, the acoustic influence was stronger in peripheral visual representations, in good concordance with prior reports on anatomical projections from auditory areas to peripheral representations in occipital cortex.
Similarly, we find that acoustic stimuli modulate neural responses in visual temporal association cortex (area TE). Recordings of neural activity in alert animals demonstrate a modulatory influence on neural responses, but only minimal responses to acoustic stimulation alone. Using computational tools to characterize this acoustic influence we find that the presence of sounds enhances the trial to trial reliability of neural responses and increases the ability to correctly decode which of a set of visual scenes was presented. This result hence suggests that sounds increase the encoded visual information.},
web_url = {http://imrf.mcmaster.ca/IMRF/ocs3/index.php/imrf/2011/paper/view/135},
event_name = {12th International Multisensory Research Forum (IMRF 2011)},
event_place = {Toulouse, France},
state = {published},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Conference{ StoewerSD2011,
title = {New approaches for the analysis of awake monkey fMRI data: fMRI
Sandbox},
year = {2011},
month = {10},
volume = {12},
pages = {17},
abstract = {fMRI experiments with awake non-human primates (NHP) have become more widespread in
recent years. However, the standard fMRI analysis tools designed for human experiments are
not well suited for analysis of NHP fMRI data collected at high fields. There are several reasons
for this, including the trial-based nature of NHP experiments, with inter-trial periods being of
no interest, and various artefacts that may result from field changes due to animal movement.
We demonstrate an approach that allows us to address some of these issues. We have implemented
a software toolbox, fMRI Sandbox (http://www.kyb.tuebingen.mpg.de/ stoewer),
for semi-automated application of these processing steps that interfaces with SPM software.
Here, we demonstrate that our methodology provides significant improvements for the analysis
of awake monkey fMRI data acquired at high-field. The method may also be useful for
clinical applications with subjects that are unwilling or unable to remain motionless for the
whole duration of a functional scan.},
web_url = {http://www.neuroschool-tuebingen-nena.de/index.php?id=284},
event_name = {12th Conference of Junior Neuroscientists of Tübingen (NeNA 2011)},
event_place = {Heiligkreuztal, Germany},
state = {published},
author = {Stoewer S{stoewer}{Department Physiology of Cognitive Processes}, Sigala N{natasha}{Department Physiology of Cognitive Processes} and Duncan J}
}

@Conference{ PerrodinKLP2011_2,
title = {Voice cells in the primate temporal lobe},
year = {2011},
month = {10},
volume = {12},
pages = {14},
abstract = {Communication signals are important for social interactions and survival and are thought to
receive specialized processing in the visual and auditory systems. Whereas the neural processing
of faces by face clusters and face cells has been repeatedly studied, less is known about
the neural representation of voice content. Recent functional magnetic resonance imaging
(fMRI) studies have localized voice-preferring regions in the primate temporal lobe, but the
hemodynamic response cannot directly assess neurophysiological properties. We investigated
the responses of neurons in an fMRI-identified voice cluster in awake monkeys, and here we
provide the first systematic evidence for voice cells. "Voice cells" were identified, in analogy
to "face cells", as neurons responding at least 2-fold stronger to conspecific voices than to
"nonvoice" sounds or heterospecific voices. Importantly, whereas face clusters are thought
to contain high proportions of face cells responding broadly to many faces, we found that
voice clusters contain moderate proportions of voice cells. Furthermore, individual voice cells
exhibit high stimulus selectivity. The results reveal the neurophysiological bases for fMRIdefined
voice clusters in the primate brain and highlight potential differences in how the
auditory and visual systems generate selective representations of communication signals.},
web_url = {http://www.neuroschool-tuebingen-nena.de/index.php?id=284},
event_name = {12th Conference of Junior Neuroscientists of Tübingen (NeNA 2011)},
event_place = {Heiligkreuztal, Germany},
state = {published},
author = {Perrodin C{cperrodin}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Petkov CI{chrisp}}
}

@Conference{ Aggelopoulos2011,
title = {The representation of objects in the inferior temporal cortex of the macaque monkey},
year = {2011},
month = {6},
day = {27},
event_name = {Life and Brain Center, University of Bonn Medical Center},
event_place = {Bonn, Germany},
state = {published},
author = {Aggelopoulos N{aggelopoulos}{Department Physiology of Cognitive Processes}}
}

@Conference{ GottschalkMEP2011,
title = {Responsive MR Imaging Probes to Monitor Synaptic Glutamate Fluctuations in the Brain},
year = {2011},
month = {6},
abstract = {mediator of excitatory signals in the nervous system and is
involved in nearly all aspects of normal brain functioning (cognition, memory, learning). Our idea was to develop glutamate ‘responsive’ magnetic resonance imaging (MRI) contrast agents (CAs) to image changes in specific brain regions upon neural activation. As CAs directly responsive to glutamate would not be feasible due to the very short half-life of glutamate in the extracellular space, we chose CAs that bind to glutamate receptors instead (to be specific metabotropic glutamate-receptor subtype 5 (mGluR5)), by this increasing image contrast. Ideally,
upon glutamate-binding to the receptor (e.g. after glutamaterelease at the synapse) the CA will be released, hence leading to a reduction in image-contrast, followed by a restoration of equilibrium and re-binding of the CA to the receptor. These events are believed to occur over a period of seconds allowing data acquisition using modern FLASH pulse techniques[1]. Here, we present a proof-of-concept study for such ‘indirect’ glutamate-responsive MRI CAs. 
Methods: We have designed and synthesized different prospective CAs derived from various potent mGluR5-receptor
antagonists (alkynes like MPEP, MTEP and dipyridyl/heterobiaryl amides) coupled to DOTA-derived macrocyclic lanthanidechelates. The CAs were evaluated in cultured primary cortical rat astrocytes, expressing mGluR5 (verified by immunofluorescence). MRI-measurements to examine the ability of the CAs for cellular labeling were done with a 3T human whole body scanner. Antagonistic potency of the CAs was assessed with a calcium fluorescence assay, by which glutamate induced intracellular calcium-transients mediated by mGluR5 were measured. Antagonistic activity of the CAs was calculated as changes in EC50 of glutamate. Receptor binding was measured for the dipyridyl derivaties, as these compounds have an inherent fluorescence that changes upon binding. Commercially
available receptor membrane preparations containing human
mGluR5A were used for these experiments. 
Results: Two of the gadolinium complexes retained significant antagonistic activity, one in each structural class. For the alkyne-derivative, about a threefold increase of the EC50(glutamate) (100μM CA, 15min, P<0.001) was found while under similar conditions the cellular relaxation rate R1,cell increased to 126% of control (100μM, 45 minutes incubation time, P<0.001). The CA derived from dipyridyl amides increased the EC50(glutamate) about fourfold (p<0.001) and the R1,cell to 115% (p<0.05). Fluorescence measurements of the latter CA showed enhanced emission upon binding to mGluR5-membrane preparations. This was reversed when increasing concentrations of glutamate were added, consistent with the a reversibility of CA-receptor binding Conclusions: Using primary rat astrocytes as cellular model system to investigate newly developed glutamate-responsive MRI contrast agents, we were able to identify two promising candidates. These CAs are based on the structures of antagonists to mGluR5 and our studies establish the validity of the concept, by which it might be possible to use MRI to image transient changes in the neurotransmitter glutamate.},
file_url = {fileadmin/user_upload/files/publications/2011/EMIM-2011-Gottschalk.pdf},
web_url = {http://www.e-smi.eu/index.php?id=2415},
event_name = {6th European Molecular Imaging Meeting (EMIM 2011)},
event_place = {Leiden, Netherlands},
state = {published},
author = {Gottschalk S{sgott}{Department High-Field Magnetic Resonance}, Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Engelmann J{joern}{Department High-Field Magnetic Resonance} and Parker D}
}

@Conference{ bartels2011,
title = {Higher-level motion processing in the human brain},
year = {2011},
month = {5},
day = {12},
event_name = {Institut für Neurobiologie, Universität Tübingen},
event_place = {Tübingen, Germany},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Article{ 6395,
title = {Causal relationships between frequency bands of extracellular signals in visual cortex revealed by an information theoretic analysis},
journal = {Journal of Computational Neuroscience},
year = {2010},
month = {12},
volume = {29},
number = {3},
pages = {547-566},
web_url = {http://www.springerlink.com/content/l065117183504416/fulltext.pdf},
state = {published},
DOI = {10.1007/s10827-010-0236-5},
author = {Besserve M{besserve}{Department Empirical Inference}{Department Physiology of Cognitive Processes}, Sch\"olkopf B{bs}{Department Empirical Inference}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Article{ 6902,
title = {Disrupting Parietal Function Prolongs Dominance Durations in Binocular Rivalry},
journal = {Current Biology},
year = {2010},
month = {12},
volume = {20},
number = {23},
pages = {2106-2111},
abstract = {Human brain imaging studies of bistable perceptual phenomena revealed that frontal and parietal areas are activated during perceptual switches between the two conflicting percepts [1,2,3]. However, these studies do not provide information about causality, i.e., whether activity reports a consequence or a cause of the perceptual change. Here we used functional magnetic resonance imaging to individually localize four parietal regions involved in perceptual switches during binocular rivalry in 15 subjects and subsequently disturbed their neural processing and that of a control site using 2 Hz repetitive transcranial magnetic stimulation (TMS) during binocular rivalry. We found that TMS over one of the sites, the right intraparietal sulcus (IPS), prolonged the periods of stable percepts. Additionally, the more lateralized the blood oxygen level-dependent signal was in IPS, the more lateralized the TMS effects were. Lateralization varied considerably across subjects, with a right-hemispheric bias. Control replay e
xperiments rule out nonspecific effects of TMS on task performance, reaction times, or eye blinks. Our results thus demonstrate a causal, destabilizing, and individually lateralized effect of normal IPS function on perceptual continuity in rivalry. This is in accord with a role of IPS in perceptual selection, relating its role in rivalrous perception to that in attention [4,5,6].},
web_url = {http://www.sciencedirect.com/science/article/pii/S0960982210013618},
state = {published},
DOI = {10.1016/j.cub.2010.10.046},
author = {Zaretskaya N{nataliya}{Department Physiology of Cognitive Processes}{Department High-Field Magnetic Resonance}, Thielscher A{thielscher}{Department High-Field Magnetic Resonance}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Article{ 6854,
title = {In Vivo Characterization of a Smart MRI Agent That Displays an Inverse Response to Calcium Concentration},
journal = {ACS Chemical Neuroscience},
year = {2010},
month = {12},
volume = {1},
number = {12},
pages = {819-828},
abstract = {Contrast agents for magnetic resonance imaging (MRI) that exhibit sensitivity toward specific ions or molecules represent a challenging but attractive direction of research. Here a Gd3+ complex linked to an aminobis(methylenephosphonate) group for chelating Ca2+ was synthesized and investigated. The longitudinal relaxivity (r1) of this complex decreases during the relaxometric titration with Ca2+ from 5.76 to 3.57 mM&amp;amp;#8722;1 s&amp;amp;#8722;1 upon saturation. The r1 is modulated by changes in the hydration number, which was confirmed by determination of the luminescence emission lifetimes of the analogous Eu3+ complex. The initial in vivo characterization of this responsive contrast agent was performed by means of electrophysiology and MRI experiments. The investigated complex is fully biocompatible, having no observable effect on neuronal function after administration into the brain ventricles or parenchyma. Distribution studies demonstrated that the diffusivity
of this
agent is
significantly lower compared with that of gadolinium&amp;amp;#8722;diethylenetriaminepentaacetic acid (Gd&amp;amp;#8722;DTPA).},
web_url = {http://pubs.acs.org/doi/pdf/10.1021/cn100083a},
state = {published},
DOI = {10.1021/cn100083a},
author = {Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, Canals S{canals}, Henig J, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Mayer HA, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Angelovski G{goran}{Department Physiology of Cognitive Processes}}
}

@Article{ 6403,
title = {Sensory information in local field potentials and spikes from visual and auditory cortices: time scales and frequency bands},
journal = {Journal of Computational Neuroscience},
year = {2010},
month = {12},
volume = {29},
number = {3},
pages = {533-545},
file_url = {/fileadmin/user_upload/files/publications/Belitski_JCompNeurosci_10_6403[0].pdf},
web_url = {http://www.springerlink.com/content/a7731565r9828434/fulltext.pdf},
state = {published},
DOI = {10.1007/s10827-010-0230-y},
author = {Belitski A{belitski}{Department Physiology of Cognitive Processes}, Panzeri S{stefano}, Magri C{cmagri}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ 5526,
title = {A modeler's view on the spatial structure of intrinsic horizontal connectivity in the neocortex},
journal = {Progress in Neurobiology},
year = {2010},
month = {11},
volume = {92},
number = {3},
pages = {277-292},
abstract = {Most current computational models of neocortical networks assume a homogeneous and isotropic arrangement of local synaptic couplings between neurons. Sparse, recurrent connectivity is typically implemented with simple statistical wiring rules. For spatially extended networks, however, such random graph models are inadequate because they ignore the traits of neuron geometry, most notably various distance dependent features of horizontal connectivity. It is to be expected that such non-random structural attributes have a great impact, both on the spatio-temporal activity dynamics and on the biological function of neocortical networks. Here we review the neuroanatomical literature describing long-range horizontal connectivity in the neocortex over distances of up to eight millimeters, in various cortical areas and mammalian species. We extract the main common features from these data to allow for improved models of large-scale cortical networks. Such models include, next to short-range neighborhood coupling, also long-range patchy connections.

We show that despite the large variability in published neuroanatomical data it is reasonable to design a generic model which generalizes over different cortical areas and mammalian species. Later on, we critically discuss this generalization, and we describe some examples of how to specify the model in order to adapt it to specific properties of particular cortical areas or species.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T0R-507BHVR-1-F&_cdi=4869&_user=29041&_pii=S0301008210001103&_origin=browse&_coverDate=11%2F30%2F2010&_sk=999079996&view=c&wchp=dGLbVtz-zSkWA&md5=211d52705439832f7161a8d36ce56c29&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.pneurobio.2010.05.001},
author = {Voges N, Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}, Aertsen A and Rotter S}
}

@Article{ Logothetis2010_2,
title = {Bold claims for optogenetics},
journal = {Nature},
year = {2010},
month = {11},
volume = {468},
number = {7323},
pages = {E3-E4},
abstract = {In a recent Letter to Nature, Lee and colleagues1 combined optogenetic stimulation with functional magnetic resonance imaging (ofMRI) to examine the relationship between pyramidal-cell spiking and the blood oxygenation level dependent (BOLD) signal. To do so, they injected an adeno-associated viral vector into the primary motor cortex (M1) of adult rats to drive the expression of channelrhodopsin (ChR2) in cortical projection neurons, thus making them sensitive to light1. The authors then used combined light stimulation and functional magnetic resonance imaging (fMRI) to examine the effects of selective activation of the light-sensitive pyramidal cells on the BOLD signal, as well as to probe the value of this methodology for mapping brain connectivity. They found that excitation of these neurons induced positive BOLD signals both in the injected M1 region and in remote target thalamic nuclei receiving direct projections from that region, and concluded that ofMRI reliably links positive BOLD signals with increased local neuronal excitation. However, their analysis neglects the almost immediate activation of other circuits that could lead to the generation of BOLD signals through local perisynaptic rather than spiking activity. Their experiments therefore do not pin down the identity of the specific neuronal signals that give rise to the BOLD signal.},
web_url = {http://www.nature.com/nature/journal/v468/n7323/pdf/nature09532.pdf},
state = {published},
DOI = {10.1038/nature09532},
author = {Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 6855,
title = {Local field potentials, BOLD and spiking activity: Relationships and physiological mechanisms},
journal = {Nature Precedings},
year = {2010},
month = {11},
volume = {2010},
pages = {1-27},
abstract = {Extracellular voltage fluctuations (local field potentials, LFPs) reflecting neural mass action are ubiquitous across species and brain regions. Numerous studies have characterized the properties of LFP signals in the cortex to study sensory and motor computations as well as cognitive processes like attention, perception and memory. In addition, its extracranial counterpart – the electroencephalogram – is widely used in clinical applications. However, the link between LFP signals and the underlying activity of local populations of neurons is still largely elusive. For the LFP to aid our understanding of cortical computation, however, we need to know as precisely as possible what aspects of neural mass action it reflects. In this chapter, we examine recent advances and results regarding the origin, the feature selectivity and the spatial resolution of the local field potential and discuss its relationship to local spiking activity as well as the BOLD signal used in fMRI. We place particular focus on the gamm
a-band of the local field potential since it has long been implicated to play an important role in sensory processing. We conclude that in contrast to spikes, the local field potential does not measure the output of the computation performed by a cortical circuit, but are rather indicative of the synaptic and dendritic processes, as well as the dynamics of cortical computation.},
file_url = {/fileadmin/user_upload/files/publications/BerensEtAl2010_LFP_[0].pdf},
web_url = {http://precedings.nature.com/documents/5216/version/1/files/npre20105216-1.pdf},
state = {published},
DOI = {10101/npre.2010.5216.1},
author = {Berens P{berens}{Research Group Computational Vision and Neuroscience}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Tolias AS{atolias}{Department Physiology of Cognitive Processes}}
}

@Article{ 6317,
title = {Behavioral, electrophysiological and histopathological consequences of systemic manganese administration in MEMRI},
journal = {Magnetic Resonance Imaging},
year = {2010},
month = {10},
volume = {28},
number = {8},
pages = {1165-1174},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T9D-4Y6T7WF-9-F&_cdi=5112&_user=29041&_pii=S0730725X09003142&_orig=search&_coverDate=01%2F21%2F2010&_sk=999999999&view=c&wchp=dGLbVzb-zSkzS&md5=da161aa76792a},
state = {published},
DOI = {10.1016/j.mri.2009.12.022},
author = {Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}, Canals S{canals}, Simanova I and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 6791,
title = {Binocular rivalry: A time dependence of eye and stimulus contributions},
journal = {Journal of Vision},
year = {2010},
month = {10},
volume = {10},
number = {12:3},
pages = {1-14},
abstract = {In binocular rivalry, the visual percept alternates stochastically between two dichoptically presented stimuli. It is established that both processes related to the eye of origin and binocular, stimulus-related processes account for these fluctuations in conscious perception. Here we studied how their relative contributions vary over time. We applied brief disruptions to rivalry displays, concurrent with an optional eye swap, at varying time intervals after one stimulus became visible (dominant). We found that early in a dominance phase the dominant eye determined the percept by stabilizing its own contribution (regardless of the stimulus), with an additional yet weaker stabilizing contribution of the stimulus (regardless of the eye). Their stabilizing contributions declined in parallel with time so that late in a dominance phase the stimulus (and in some cases also the eye-based) contribution turned negative, favoring a perceptual (or ocular) switch. Our findings show that depending on the time, first proces
ses related to the eye of origin and then those related to the stimulus can have a greater net influence on the stability of the conscious percept. Their co-varying change may be due to feedback from image- to eye-of-origin representations.},
web_url = {http://www.journalofvision.org/content/10/12/3.full.pdf+html},
state = {published},
DOI = {10.1167/10.12.3},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 6385,
title = {Coupling of neural activity and fMRI-BOLD in the motion area MT},
journal = {Magnetic Resonance in Medicine},
year = {2010},
month = {10},
volume = {28},
number = {8},
pages = {1087-1094},
abstract = {The fMRI-BOLD contrast is widely used to study the neural basis of sensory perception and cognition. This signal, however, reflects neural activity only indirectly, and the detailed mechanisms of neurovascular coupling and the neurophysiological correlates of the BOLD signal remain debated. Here we investigate the coupling of BOLD and electrophysiological signals in the motion area MT of the macaque monkey by simultaneously recording both signals. Our results demonstrate that a prominent neuronal response property of area MT, so-called motion opponency, can be used to induce dissociations of BOLD and neuronal firing. During the presentation of a stimulus optimally driving the local neurons, both field potentials [local field potentials (LFPs)] and spiking activity [multi-unit activity (MUA)] correlated with the BOLD signal. When introducing the motion opponency stimulus, however, correlations of MUA with BOLD were much reduced, and LFPs were a much better predictor of the BOLD signal than MUA. In addition, fo
r a subset of recording sites we found positive BOLD and LFP responses in the presence of decreases in MUA, regardless of the stimulus used. Together, these results demonstrate that correlations between BOLD and MUA are dependent on the particular site and stimulus paradigm, and foster the notion that the fMRI-BOLD signal reflects local dendrosomatic processing and synaptic activity rather than principal neuron spiking responses.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T9D-4YDYW8B-1-7&_cdi=5112&_user=29041&_pii=S0730725X09003208&_origin=search&_coverDate=10%2F31%2F2010&_sk=999719991&view=c&wchp=dGLbVtb-zSkzS&md5=4b61d8e6911476717a27cd23535a639b&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.mri.2009.12.028},
author = {Lippert MT{mlippert}{Department Physiology of Cognitive Processes}, Steudel T{steudel}{Department Physiology of Cognitive Processes}, Ohl F, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ SultanHMSL2010,
title = {Flat map areal topography in Macaca mulatta based on combined MRI and histology},
journal = {Magnetic Resonance Imaging},
year = {2010},
month = {10},
volume = {28},
number = {8},
pages = {1159-1164},
abstract = {Flattened representations are a useful approach to represent the convoluted complex surface of the neocortex of primates and other large-brained mammals. In this study, we compared the flattened representation of neocortical areas obtained from the recently published MRI and histology atlas of the rhesus monkey brain (Saleem KS, Logothetis NK. A combined MRI and histology atlas of the rhesus monkey brain in stereotaxic coordinates. London: Academic; 2007) with other previously published maps. Our results confirm that flat map representations are advantageous due to their ease of use and that current flat maps are well comparable to each other. Some differences arise due to different distinguishing criteria and here too flat maps can help to reveal them.},
web_url = {http://www.sciencedirect.com/science?_ob=MiamiImageURL&_cid=271222&_user=29041&_pii=S0730725X1000086X&_check=y&_origin=&_coverDate=31-Oct-2010&view=c&wchp=dGLzVlB-zSkzk&md5=dc56dbea6e82bd698ef5b3393ef1e1fe/1-s2.0-S0730725X1000086X-main.pdf},
state = {published},
DOI = {10.1016/j.mri.2010.03.023},
author = {Sultan F, Hamodeh S, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Saleem KS and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 6597,
title = {Flexible, phase-matched, linear receive arrays for high-field MRI in monkeys},
journal = {Magnetic Resonance Imaging},
year = {2010},
month = {10},
volume = {28},
number = {8},
pages = {1183-1191},
abstract = {High signal-to-noise ratios (SNR) are essential for high-resolution anatomical and functional MRI. Phased arrays are advantageous for this but have the drawback that they often have inflexible and bulky configurations. Particularly in experiments where functional MRI is combined with simultaneous electrophysiology, space constraints can be prohibitive. To this end we developed a highly flexible multiple receive element phased array for use on anesthetized monkeys. The elements are interchangeable and different sizes and combinations of coil elements can be used, for instance, combinations of single and overlapped elements. The preamplifiers including control electronics are detachable and can serve a variety of prefabricated and phase matched arrays of different configurations, allowing the elements to always be placed in close proximity to the area of interest. Optimizing performance of the individual elements ensured high SNR at the cortical surface as well as in deeper laying structures. Performance of a v
ariety of arrangements of gapped linear arrays was evaluated at 4.7 and 7T in high-resolution anatomical and functional MRI.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T9D-4YXKFP6-3-K&_cdi=5112&_user=29041&_pii=S0730725X10000895&_orig=search&_coverDate=04%2F24%2F2010&_sk=999999999&view=c&wchp=dGLzVlb-zSkzV&md5=21e78b6f15291},
state = {published},
DOI = {10.1016/j.mri.2010.03.026},
author = {Goense J{jozien}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Merkle H{hellmut}}
}

@Article{ 6179,
title = {Frontoparietal activity with minimal decision and control in the awake Macaque at 7T},
journal = {Magnetic Resonance Imaging},
year = {2010},
month = {10},
volume = {28},
number = {8},
pages = {1120-1128},
abstract = {Previous imaging work has identified a frontoparietal network in the human brain involved in many cognitive functions, as well as in simple updates of attended information. We examined the activation of frontoparietal areas during visual stimulation in the awake, fixating monkey, in order to determine if a similar network is present in the monkey brain and direct future electrophysiological recordings. We measured activity with BOLD fMRI in three animals and analysed the data individually for each animal, and at group level.    We found reliable activations in lateral prefrontal and parietal areas, even though task-related decision making was minimal, as a response to simple update of visual information.  These activations were significant for each individual animal,  as well as at group level. Similar to human imaging results the update of visual input was enough to activate the frontoparietal cortex in the macaque brain, a network which is normally associated with complex cognitive control processes.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6T9D-4Y960VY-6-C&amp;_cdi=5112&amp;_user=29041&amp;_pii=S0730725X09003166&amp;_orig=search&amp;_coverDate=02%2F01%2F2010&amp;_sk=999999999&amp;view=c&amp;wchp},
state = {published},
DOI = {10.1016/j.mri.2009.12.024},
author = {Stoewer S{stoewer}{Department Physiology of Cognitive Processes}, Ku S-P{shihpi}{Department Physiology of Cognitive Processes}, Goense J{jozien}{Department Physiology of Cognitive Processes}, Steudel T{steudel}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Duncan J and Sigala N{natasha}{Department Physiology of Cognitive Processes}}
}

@Article{ 6665,
title = {Integration of EEG source imaging and fMRI during continuous viewing of natural movies},
journal = {Magnetic Resonance Imaging},
year = {2010},
month = {10},
volume = {28},
number = {8},
pages = {1135-1142},
web_url = {http://www.sciencedirect.com/science/article/pii/S0730725X10001335},
state = {published},
DOI = {10.1016/j.mri.2010.03.042},
author = {Whittingstall K{kevin}{Department Physiology of Cognitive Processes}, Bartels A{abartels}{Department Physiology of Cognitive Processes}, Singh V{vsingh}{Department Physiology of Cognitive Processes}, Kwon S{soyoung}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 6272,
title = {Relationship between neural and hemodynamic signals during spontaneous activity studied with temporal kernel CCA},
journal = {Magnetic Resonance Imaging},
year = {2010},
month = {10},
volume = {28},
number = {8},
pages = {1095-1103},
abstract = {Functional magnetic resonance imaging (fMRI) based on the so-called blood oxygen level-dependent (BOLD) contrast is a powerful tool for studying brain function not only locally but also on the large scale. Most studies assume a simple relationship between neural and BOLD activity, in spite of the fact that it is important to elucidate how the “when” and “what” components of neural activity are correlated to the “where” of fMRI data. Here we conducted simultaneous recordings of neural and BOLD signal fluctuations in primary visual (V1) cortex of anesthetized monkeys. We explored the neurovascular relationship during periods of spontaneous activity by using temporal kernel canonical correlation analysis (tkCCA). tkCCA is a multivariate method that can take into account any features in the signals that univariate analysis cannot. The method detects filters in voxel space (for fMRI data) and in frequency–time space (for neural data) that maximize the neurovascular correlation without any assumption of a hemodynamic response function (HRF). Our results showed a positive neurovascular coupling with a lag of 4–5 s and a larger contribution from local field potentials (LFPs) in the γ range than from low-frequency LFPs or spiking activity. The method also detected a higher correlation around the recording site in the concurrent spatial map, even though the pattern covered most of the occipital part of V1. These results are consistent with those of previous studies and represent the first multivariate analysis of intracranial electrophysiology and high-resolution fMRI.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6T9D-4Y6T7WF-2-C&amp;_cdi=5112&amp;_user=29041&amp;_pii=S0730725X09003087&amp;_orig=search&amp;_coverDate=01%2F21%2F2010&amp;_sk=999999999&amp;view=c&amp;wchp},
state = {published},
DOI = {10.1016/j.mri.2009.12.016},
author = {Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Biessmann F{fbiessma}{Department Physiology of Cognitive Processes}, Meinecke FC, M\"uller K-R{klaus}, Augath M{mark}{Department Physiology of Cognitive Processes}, Oeltermann A{axel} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 6524,
title = {Testing methodologies for the nonlinear analysis of causal relationships in neurovascular coupling},
journal = {Magnetic Resonance Imaging},
year = {2010},
month = {10},
volume = {28},
number = {8},
pages = {1113-1119},
abstract = {We investigated the use and implementation of a nonlinear methodology for establishing which changes in neurophysiological signals cause changes in the blood oxygenation level-dependent (BOLD) contrast measured in functional magnetic resonance imaging. Unlike previous analytical approaches, which used linear correlation to establish covariations between neural activity and BOLD, we propose a directed information-theoretic measure, the transfer entropy, which can elucidate even highly nonlinear causal relationships between neural activity and BOLD signal. In this study we investigated the practicality of such an analysis given the limited data samples that can be collected experimentally due to the low temporal resolution of BOLD signals. We implemented several algorithms for the estimation of transfer entropy and we tested their effectiveness using simulated local field potentials (LFPs) and BOLD data constructed to match the main statistical properties of real LFP and BOLD signals measured simultaneously in monkey primary visual cortex. We found that using the advanced methods of entropy estimation implemented and described here, a transfer entropy analysis of neurovascular coupling based on experimentally attainable data sets is feasible.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T9D-4YX0BPK-2-7&_cdi=5112&_user=29041&_pii=S0730725X10000913&_orig=search&_coverDate=04%2F21%2F2010&_sk=999999999&view=c&wchp=dGLbVlb-zSkWA&md5=2c97d4947bf1c},
state = {published},
DOI = {10.1016/j.mri.2010.03.028},
author = {L\"udtke N{nludtke}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Article{ 6794,
title = {The effects of electrical microstimulation on cortical signal propagation},
journal = {Nature Neuroscience},
year = {2010},
month = {10},
volume = {13},
number = {10},
pages = {1283-1291},
abstract = {Electrical stimulation has been used in animals and humans to study potential causal links between neural activity and specific cognitive functions. Recently, it has found increasing use in electrotherapy and neural prostheses. However, the manner in which electrical stimulation–elicited signals propagate in brain tissues remains unclear. We used combined electrostimulation, neurophysiology, microinjection and functional magnetic resonance imaging (fMRI) to study the cortical activity patterns elicited during stimulation of cortical afferents in monkeys. We found that stimulation of a site in the lateral geniculate nucleus (LGN) increased the fMRI signal in the regions of primary visual cortex (V1) that received input from that site, but suppressed it in the retinotopically matched regions of extrastriate cortex. Consistent with previous observations, intracranial recordings indicated that a short excitatory response occurring immediately after a stimulation pulse was followed by a long-lasting inhibition. Following microinjections of GABA antagonists in V1, LGN stimulation induced positive fMRI signals in all of the cortical areas. Taken together, our findings suggest that electrical stimulation disrupts cortico-cortical signal propagation by silencing the output of any neocortical area whose afferents are electrically stimulated.},
web_url = {http://www.nature.com/neuro/journal/v13/n10/pdf/nn.2631.pdf},
state = {published},
DOI = {10.1038/nn.2631},
author = {Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Augath M{mark}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Rauch A{arauch}{Department Physiology of Cognitive Processes}, Sultan F, Goense J{jozien}{Department Physiology of Cognitive Processes}, Oeltermann A{axel} and Merkle H{hellmut}}
}

@Article{ 6441,
title = {The Thatcher illusion in humans and monkeys},
journal = {Proceedings of the Royal Society of London B},
year = {2010},
month = {10},
volume = {277},
number = {1696},
pages = {2973-2981},
abstract = {Primates possess the remarkable ability to differentiate faces of group members and to extract relevant information about the individual directly from the face. Recognition of conspecific faces is achieved by means of holistic processing, i.e. the processing of the face as an unparsed, perceptual whole, rather than as the collection of independent features (part-based processing). The most striking example of holistic processing is the Thatcher illusion. Local changes in facial features are hardly noticeable when the whole face is inverted (rotated 180°), but strikingly grotesque when the face is upright. This effect can be explained by a lack of processing capabilities for locally rotated facial features when the face is turned upside down. Recently, a Thatcher illusion was described in the macaque monkey analogous to that known from human investigations. Using a habituation paradigm combined with eye tracking, we address the critical follow-up questions raised in the aforementioned study to show the Thatch
er illusion as a function of the observer‘s species (humans and macaques), the stimulus‘ species (humans and macaques) and the level of perceptual expertise (novice, expert).},
web_url = {http://rspb.royalsocietypublishing.org/content/early/2010/05/13/rspb.2010.0438.full.pdf+html},
state = {published},
DOI = {10.1098/rspb.2010.0438},
author = {Dahl CD{dahl}{Department Human Perception, Cognition and Action}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, B\"ulthoff HH{hhb}{Department Human Perception, Cognition and Action} and Wallraven C{walli}{Department Human Perception, Cognition and Action}}
}

@Article{ 6795,
title = {Millisecond encoding precision of auditory cortex neurons},
journal = {Proceedings of the National Academy of the United States of America},
year = {2010},
month = {9},
volume = {107},
number = {39},
pages = {16976-16981},
abstract = {Neurons in auditory cortex are central to our perception of sounds. However, the underlying neural codes, and the relevance of millisecond precise spike timing in particular, remain debated. Here we addressed this issue in the auditory cortex of alert non-human primates by quantifying the amount of information carried by precise spike timing about complex sounds presented for extended periods of time (random tone sequences and natural sounds). We investigated the dependence of stimulus information on the temporal precision at which spike times were registered, and found that registering spikes at a precision coarser than a few milliseconds significantly reduced the encoded information. This demonstrates that auditory cortex neurons can carry stimulus information at high temporal precision. In addition, we found that the main determinant of finely timed information was rapid modulation of the firing rate, while higher-order correlations between spike times contributed negligibly. While the neural coding precis
ion was high for random tone sequences and natural sounds, the information lost at a precision coarser than a few milliseconds was higher for the stimulus sequence that varied on a faster time scale (random tones), suggesting that the precision of cortical firing depends on the stimulus dynamics. Together, these results provide a neural substrate for recently reported behavioral relevance of precisely timed activity patterns with auditory cortex. In addition, they highlight the importance of millisecond precise neural coding as general functional principle of auditory processing – from the periphery to cortex.},
web_url = {http://www.pnas.org/content/107/39/16976.full.pdf+html},
state = {published},
DOI = {10.1073/pnas.1012656107},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Article{ 6683,
title = {The Role of the Primary Visual Cortex in Perceptual Suppression of Salient Visual Stimuli},
journal = {Journal of Neuroscience},
year = {2010},
month = {9},
volume = {30},
number = {37},
pages = {12353-12365},
abstract = {The role of primary visual cortex (area V1) in subjective perception has intrigued students of vision for decades. Specifically, the extent to which the activity of different types of cells (monocular versus binocular) and electrophysiological signals (i.e. local field potentials versus spiking activity) reflect perception is still debated. To address these questions we recorded from area V1 of the macaque using tetrodes during the paradigm of binocular flash suppression, where incongruent images presented dichoptically compete for perceptual dominance. We found that the activity of a minority (20%) of neurons reflect the perceived visual stimulus and these cells exhibited perceptual modulations substantially weaker in comparison to their sensory modulation induced by congruent stimuli. Importantly, perceptual modulations were found equally often for monocular and binocular cells, demonstrating that perceptual competition in V1 involves mechanisms across both types of neurons. The power of the local field pot
ential (LFP) also showed moderate perceptual modulations with similar percentages of sites showing significant effects across frequency bands (18-22%). The possibility remains that perception may be strongly reflected in more elaborate aspects of activity in V1 circuits (e.g. specific neuronal subtypes) or perceptual states might have a modulatory role on more intricate aspects of V1 firing patterns (e.g. synchronization), not necessarily altering the firing rates of single cells or the LFP power dramatically.},
web_url = {http://www.jneurosci.org/cgi/reprint/30/37/12353},
state = {published},
DOI = {10.1523/JNEUROSCI.0677-10.2010},
author = {Keliris GA{george}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Tolias AS{atolias}{Department Physiology of Cognitive Processes}}
}

@Article{ 6217,
title = {Understanding the relationships between spike rate and delta/gamma frequency bands of LFPs and EEGs using a local cortical network model},
journal = {NeuroImage},
year = {2010},
month = {9},
volume = {52},
number = {3},
pages = {956-972},
abstract = {Despite the widespread use of EEGs to measure the large-scale dynamics of the human brain, little is known on how the dynamics of EEGs relates to that of the underlying spike rates of cortical neurons. However, progress was made by recent neurophysiological experiments reporting that EEG delta-band phase and gamma-band amplitude reliably predict some complementary aspects of the time course of spikes of visual cortical neurons. To elucidate the mechanisms behind these findings, here we hypothesize that the EEG delta phase reflects shifts of local cortical excitability arising from slow fluctuations in the network input due to entrainment to sensory stimuli or to fluctuations in ongoing activity, and that the resulting local excitability fluctuations modulate both the spike rate and the engagement of excitatory–inhibitory loops producing gamma-band oscillations. We quantitatively tested these hypotheses by simulating a recurrent network of excitatory and inhibitory neurons stimulated with dynamic inputs prese
nting temporal regularities similar to that of thalamic responses during naturalistic visual stimulation and during spontaneous activity. The network model reproduced in detail the experimental relationships between spike rate and EEGs, and suggested that the complementariness of the prediction of spike rates obtained from EEG delta phase or gamma amplitude arises from nonlinearities in the engagement of excitatory–inhibitory loops and from temporal modulations in the amplitude of the network input, which respectively limit the predictability of spike rates from gamma amplitude or delta phase alone. The model suggested also ways to improve and extend current algorithms for online prediction of spike rates from EEGs.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WNP-4Y05DJ6-5-16&amp;_cdi=6968&amp;_user=29041&amp;_pii=S1053811909013299&amp;_orig=search&amp;_coverDate=12%2F21%2F2009&amp;_sk=999999999&amp;view=c&amp;wch},
state = {published},
DOI = {10.1016/j.neuroimage.2009.12.040},
author = {Mazzoni A, Whittingstall K{kevin}{Department Physiology of Cognitive Processes}, Brunel N, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Article{ 6738,
title = {Unimodal responses prevail within the multisensory claustrum},
journal = {Journal of Neuroscience},
year = {2010},
month = {9},
volume = {30},
number = {39},
pages = {12902-12907},
abstract = {The claustrum receives afferent inputs from multiple sensory-related brain areas, prompting speculation about a role in integrating information across sensory modalities. Here we directly test this hypothesis by probing neurons in the primate claustrum for functional characteristics of multisensory processing. To this end we recorded neuronal responses to naturalistic audio-visual stimuli from the claustra of alert monkeys. Our results reveal the existence of distinct claustral zones comprised of unimodal neurons associated with the auditory and visual modalities. In a visual zone within the ventral claustrum neurons responded to visual stimuli but not to sounds, whereas in an auditory zone located within the central claustrum neurons responded to sounds but not to visual stimuli. Importantly, we find that neurons within either zone are not influenced by stimuli in the other modality and do not exhibit the typical response characteristics usually associated with multisensory processing. While these results co
nfirm the notion of the claustrum as a multisensory structure per se, they argue against the hypothesis of the claustrum serving as an integrator of sensory information.},
web_url = {http://www.jneurosci.org/cgi/reprint/30/39/12902},
state = {published},
DOI = {10.1523/JNEUROSCI.2937-10.2010},
author = {Remedios R{ryan}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ 6144,
title = {An online spike detection and spike classification algorithm capable of instantaneous resolution of overlapping spikes},
journal = {Journal of Computational Neuroscience},
year = {2010},
month = {8},
volume = {29},
number = {1-2},
pages = {127-148},
abstract = {For the analysis of neuronal cooperativity, simultaneously recorded extracellular signals from neighboring neurons need to be sorted reliably by a spike sorting method. Many algorithms have been developed to this end, however, to date, none of them manages to fulfill a set of demanding requirements. In particular, it is desirable to have an algorithm that operates online, detects and classifies overlapping spikes in real time, and that adapts to non-stationary data. Here, we present a combined spike detection and classification algorithm, which explicitly addresses these issues. Our approach makes use of linear filters to find a new representation of the data and to optimally enhance the signal-to-noise ratio. We introduce a method called “Deconfusion” which de-correlates the filter outputs and provides source separation. Finally, a set of well-defined thresholds is applied and leads to simultaneous spike detection and spike classification. By incorporating a direct feedback, the algorithm adapts to non-sta
tionary data and is, therefore, well suited for acute recordings. We evaluate our method on simulated and experimental data, including simultaneous intra/extra-cellular recordings made in slices of a rat cortex and recordings from the prefrontal cortex of awake behaving macaques. We compare the results to existing spike detection as well as spike sorting methods. We conclude that our algorithm meets all of the mentioned requirements and outperforms other methods under realistic signal-to-noise ratios and in the presence of overlapping spikes.},
web_url = {http://www.springerlink.com/content/98g8060421112744/fulltext.pdf},
state = {published},
DOI = {10.1007/s10827-009-0163-5},
author = {Franke F, Natora M, Boucsein C, Munk MHJ{munk}{Department Physiology of Cognitive Processes} and Obermayer K}
}

@Article{ 6780,
title = {Audiovisual interactions in binocular rivalry},
journal = {Journal of Vision},
year = {2010},
month = {8},
volume = {10},
number = {10:27},
pages = {1-15},
abstract = {When the two eyes are presented with dissimilar images, human observers report alternating percepts—a phenomenon coined binocular rivalry. These perceptual fluctuations reflect competition between the two visual inputs both at monocular and binocular processing stages. Here we investigated the influence of auditory stimulation on the temporal dynamics of binocular rivalry. In three psychophysics experiments, we investigated whether sounds that provide directionally congruent, incongruent, or non-motion information modulate the dominance periods of rivaling visual motion percepts. Visual stimuli were dichoptically presented random-dot kinematograms (RDKs) at different levels of motion coherence. The results show that directional motion sounds rather than auditory input per se influenced the temporal dynamics of binocular rivalry. In all experiments, motion sounds prolonged the dominance periods of the directionally congruent visual motion percept. In contrast, motion sounds abbreviated the suppression periods
of the directionally congruent visual motion percepts only when they competed with directionally incongruent percepts. Therefore, analogous to visual contextual effects, auditory motion interacted primarily with consciously perceived visual input rather than visual input suppressed from awareness. Our findings suggest that auditory modulation of perceptual dominance times might be established in a top-down fashion by means of feedback mechanisms.},
web_url = {http://www.journalofvision.org/content/10/10/27.full.pdf+html},
state = {published},
DOI = {10.1167/10.10.27},
author = {Conrad V{conrad}{Department Human Perception, Cognition and Action}{Research Group Cognitive Neuroimaging}, Bartels A{abartels}{Department Physiology of Cognitive Processes}, Kleiner M{kleinerm}{Department Human Perception, Cognition and Action} and Noppeney U{unoppe}{Research Group Cognitive Neuroimaging}}
}

@Article{ 6155,
title = {Coding and binding of colour and form in visual cortex},
journal = {Cerebral Cortex},
year = {2010},
month = {8},
volume = {20},
number = {8},
pages = {1946-1954},
abstract = {The processing of color and form is largely segregated within the visual brain. But there is also evidence to suggest that these features are coded in combination early in visual processing. Here, we combined high-resolution functional magnetic resonance imaging (fMRI) together with multivariate pattern classification to examine where in the visual cortex specific color form "conjunctions" are represented. Human subjects viewed visual displays containing colored spiral patterns. The spiral patterns could be red or green, and oriented either clockwise or counterclockwise, leading to 4 possible stimulus configurations. Two additional displays combined 2 of the above single color-form pairings, leading to double conjunctions. We applied linear classifiers to voxel activation patterns obtained while subjects viewed such displays. Our findings not only show that color and form information is coded across retinotopically defined visual areas, but also that the 2 double-conjunction stimuli can be distinguished. The
voxels most informative about conjunctions were distinct from those most informative about color or form alone. Our results indicate that conjunctions of form and color may be coded by separate functional units as early as primary visual cortex. The results of this study have implications for theories concerning the segregation and binding of color and form information.},
web_url = {http://cercor.oxfordjournals.org/cgi/reprint/bhp265v1},
state = {published},
DOI = {10.1093/cercor/bhp265},
author = {Seymour K{seymour}{Department Physiology of Cognitive Processes}, Clifford CWG{colinc}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Article{ 6105,
title = {In vivo chlorine-35, sodium-23 and proton magnetic resonance imaging of the rat brain},
journal = {NMR in Biomedicine},
year = {2010},
month = {7},
volume = {23},
number = {6},
pages = {592-600},
abstract = {In this study we demonstrate the feasibility of combined chlorine-35, sodium-23 and proton magnetic resonance imaging (MRI) at 9.4 Tesla, and present the first invivo chlorine-35 images obtained by means of MRI. With the experimental setup used in this study all measurements could be done in one session without changing the setup or moving the subject. The multinuclear measurement requires a total measurement time of 2 h and provides morphological (protons) and physiological (sodium-23, chlorine-35) information in one scanning session. Chlorine-35, sodium-23 and high resolution proton images were acquired from a phantom, a healthy rat and from a rat displaying a focal cerebral infarction. Compared to the healthy tissue a signal enhancement of a factor of 2.2 ± 0.2 in the chlorine-35 and a factor of 2.9 ± 0.6 in the sodium-23 images is observed in the areas of infarction. Exemplary unlocalized measurement of the invivo longitudinal and transversal relaxation time of chlorine-35 in a healthy rat showed multi-exponential behaviour. A biexponential fit revealed a fast and a slow relaxing component with T1,a = (1.7 ± 0.4) ms, T1,b = (25.1 ± 1.4) ms, amplitudes of A = 0.26 ± 0.02, (1–A) = 0.74 ± 0.02 and T2,a = (1.3 ± 0.1) ms, T2,b = (11.8 ± 1.1) ms, A = 0.64 ± 0.02, (1–A)  = 0.36 ± 0.02. Combined proton, sodium-23 and chlorine-35 MRI may provide a new approach for non-invasive studies of ionic regulatory processes under physiological and pathological conditions invivo.},
web_url = {http://onlinelibrary.wiley.com/doi/10.1002/nbm.1500/pdf},
state = {published},
DOI = {10.1002/nbm.1500},
author = {Kirsch S, Augath M{mark}{Department Physiology of Cognitive Processes}, Seiffge D, Schilling L and Schad LR}
}

@Article{ 6735,
title = {The Multisensory Nature of Unisensory Cortices: A Puzzle Continued},
journal = {Neuron},
year = {2010},
month = {7},
volume = {67},
number = {2},
pages = {178-180},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&amp;amp;_imagekey=B6WSS-50MW961-4-1&amp;amp;_cdi=7054&amp;amp;_user=29041&amp;amp;_pii=S0896627310005507&amp;amp;_origin=search&amp;amp;_coverDate=07%2F29%2F2010&amp;amp;_sk=9993299},
state = {published},
DOI = {10.1016/j.neuron.2010.07.012},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ Logothetis2010,
title = {Neurovascular uncoupling: much ado about nothing},
journal = {Frontiers in Neuroenergetics},
year = {2010},
month = {6},
volume = {2},
number = {2},
pages = {1-4},
web_url = {http://www.frontiersin.org/neuroenergetics/10.3389/fnene.2010.00002/full},
state = {published},
DOI = {10.3389/fnene.2010.00002},
author = {Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 6596,
title = {Complex Times for Earthquakes, Stocks, and the Brain's Activity},
journal = {Neuron},
year = {2010},
month = {5},
volume = {66},
number = {3},
pages = {329-331},
abstract = {Scale-free dynamics, with a power spectrum
following P alpha f -beta, are an intrinsic feature of many
complex processes in nature. In neural systems,
scale-free activity is often neglected in electrophysiological
research. Here, we investigate scale-free
dynamics in human brain and show that it contains
extensive nested frequencies, with the phase of lower
frequencies modulating the amplitude of higher
frequencies in an upward progression across the
frequency spectrum. The functional significance of
scale-free brain activity is indicated by task performance
modulation and regional variation, with
beta being larger in default network and visual cortex
and smaller in hippocampus and cerebellum. The
precise patterns of nested frequencies in the brain
differ from other scale-free dynamics in nature, such
as earth seismic waves and stock market fluctuations,
suggesting system-specific generative mechanisms.
Our findings reveal robust temporal structures
and behavioral significance of scale-free brain
activity and should motivate future study on its physiological
mechanisms and cognitive implications.},
file_url = {/fileadmin/user_upload/files/publications/Kayser_Neuron_preview_10_6596[0].pdf},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WSS-502FPVC-1-4&amp;_cdi=7054&amp;_user=29041&amp;_pii=S0896627310003326&amp;_orig=search&amp;_coverDate=05%2F13%2F2010&amp;_sk=999339996&amp;view=c&amp;wchp},
state = {published},
DOI = {10.1016/j.neuron.2010.04.039},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration} and Ermentrout B}
}

@Article{ HoerzerLSLR2010,
title = {Directed coupling in local field potentials of macaque V4 during visual short-term memory revealed by multivariate autoregressive models},
journal = {Frontiers in Computational Neuroscience},
year = {2010},
month = {5},
volume = {4},
number = {14},
pages = {1-13},
abstract = {Processing and storage of sensory information is based on the interaction between different neural populations rather than the isolated activity of single neurons. In order to characterize the dynamic interaction and transient cooperation of sub-circuits within a neural network, multivariate autoregressive (MVAR) models have proven to be an important analysis tool. In this study, we apply directed functional coupling based on MVAR models and describe the temporal and spatial changes of functional coupling between simultaneously recorded local field potentials in extrastriate area V4 during visual memory. Specifically, we compare the strength and directional relations of coupling based on generalized partial directed coherence (GPDC) measures while two rhesus monkeys perform a visual short-term memory task. In both monkeys we find increases in theta power during the memory period that are accompanied by changes in directed coupling. These interactions are most prominent in the low frequency range encompassing the theta band (3–12 Hz) and, more importantly, are asymmetric between pairs of recording sites. Furthermore, we find that the degree of interaction decreases as a function of distance between electrode positions, suggesting that these interactions are a predominantly local phenomenon. Taken together, our results show that directed coupling measures based on MVAR models are able to provide important insights into the spatial and temporal formation of local functionally coupled ensembles during visual memory in V4. Moreover, our findings suggest that visual memory is accompanied not only by a temporary increase of oscillatory activity in the theta band, but by a direction-dependent change in theta coupling, which ultimately represents a change in functional connectivity within the neural circuit.},
web_url = {http://www.frontiersin.org/computational_neuroscience/10.3389/fncom.2010.00014/abstract},
state = {published},
DOI = {10.3389/fncom.2010.00014},
author = {Hoerzer GM, Liebe S{sliebe}{Department Physiology of Cognitive Processes}, Schloegl A, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Article{ 6594,
title = {Synthesis and characterization of dinuclear heterometallic lanthanide complexes exhibiting MRI and luminescence response},
journal = {Dalton Transactions},
year = {2010},
month = {5},
volume = {39},
number = {24},
pages = {5721-5727},
abstract = {A molecule bearing a macrocyclic DOTA-type chelator and an acyclic chelator based on the 5-aminoisophthalamide diethylenediaminetetraacid (5A-PADDTA) was synthesized by linking these two moieties via an 
amide bond. The ligand has the possibility to complex two identical or different lanthanide ions, depending on the desire for its potential application. Luminescence studies involving titrations of the 
Eu3+ or Gd3+ complex with Tb3+ confirm the formation of heterometallic complexes, as well as the presence of different species in the solution. Comparative 1H NMR spectra of the ligand, its Eu3+ complex, and that 
containing both Eu3+ and Tb3+ proves the existence of respective monometallic or bimetallic species. NMR diffusion measurements on 5A-PADDTA as a model compound indicate the formation of aggregates upon the 
addition of Y3+ (chosen as a diamagnetic analogue of lanthanide ions). Hydration values were calculated from the respective luminescence lifetime values. They show the dominance of a q = 1 species for both ions in 
monometallic complexes, or q = 1 and q = 2 species of ions in aggregated complexes, for DOTA and 5A-PADDTA chelators, respectively.},
web_url = {http://www.rsc.org/ej/DT/2010/b925556g.pdf},
state = {published},
DOI = {10.1039/b925556g},
author = {Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, Parac-Vogt TN, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Angelovski G{goran}{Department Physiology of Cognitive Processes}}
}

@Article{ 6134,
title = {Temporal Kernel CCA and its Application in Multimodal Neuronal Data Analysis},
journal = {Machine Learning},
year = {2010},
month = {5},
volume = {79},
number = {1-2},
pages = {5-27},
abstract = {Data recorded from multiple sources sometimes exhibit non-instantaneous couplings. For simple data sets, cross-correlograms may reveal the coupling dynamics. But when dealing with high-dimensional multivariate data there is no such measure as the cross-correlogram. We propose a simple algorithm based on Kernel Canonical Correlation Analysis (kCCA) that computes a multivariate temporal filter which links one data modality to another one. The filters can be used to compute a multivariate extension of the cross-correlogram, the canonical correlogram, between data sources that have different dimensionalities and temporal resolutions. The canonical correlogram reflects the coupling dynamics between the two sources. The temporal filter reveals which features in the data give rise to these couplings and when they do so. We present results from simulations and neuroscientific experiments showing that tkCCA yields easily interpretable temporal filters and correlograms. In the experiments, we simultaneously performed electrode recordings and functional magnetic resonance imaging (fMRI) in primary visual cortex of the non-human primate. While electrode recordings reflect brain activity directly, fMRI provides only an indirect view of neural activity via the Blood Oxygen Level Dependent (BOLD) response. Thus it is crucial for our understanding and the interpretation of fMRI signals in general to relate them to direct measures of neural activity acquired with electrodes. The results computed by tkCCA confirm recent models of the hemodynamic response to neural activity and allow for a more detailed analysis of neurovascular coupling dynamics.},
file_url = {/fileadmin/user_upload/files/publications/Machine-Learning-2009-Biessmann_[0].pdf},
web_url = {http://www.springerlink.com/content/e1425487365v2227/fulltext.pdf},
state = {published},
DOI = {10.1007/s10994-009-5153-3},
author = {Biessmann F{fbiessma}{Department Physiology of Cognitive Processes}, Meinecke FC, Gretton A{arthur}{Department Empirical Inference}, Rauch A{arauch}{Department Physiology of Cognitive Processes}, Rainer G{gregor}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and M\"uller K-R{klaus}{Department Empirical Inference}}
}

@Article{ 6397,
title = {Modulation of visual neurons in the superior temporal sulcus by audio-visual congruency},
journal = {Frontiers in Integrative Neuroscience},
year = {2010},
month = {4},
volume = {4},
number = {10},
pages = {1-8},
abstract = {Our ability to identify or recognize visual objects is often enhanced by evidence provided by other
sensory modalities. Yet, where and how visual object processing benefits from the information
received by the other senses remains unclear. One candidate region is the temporal lobe, which
features neural representations of visual objects, and in which previous studies have provided
evidence for multisensory influences on neural responses. In the present study we directly tested
whether visual representations in the lower bank of the superior temporal sulcus (STS) benefit from
acoustic information. To this end, we recorded neural responses in alert monkeys passively watching
audio&amp;amp;amp;amp;amp;amp;#8208;visual scenes, and quantified the impact of simultaneously presented sounds on responses
elicited by the presentation of naturalistic visual scenes. Using methods of stimulus decoding and
information theory, we then asked whether the responses of STS neurons become more reliable and
informative in multisensory contexts. Our results demonstrate that STS neurons are indeed sensitive
to the modality composition of the sensory stimulus and show that both response timing and
amplitude are affected by simultaneously presented sounds. Importantly, information provided by
STS neurons’ responses about the particular visual stimulus being presented was highest during
congruent audio&amp;amp;amp;amp;amp;amp;#8208;visual and unimodal visual stimulation, but was reduced during incongruent
bimodal stimulation. Together, these findings demonstrate that higher visual representations in the
STS not only convey information about the visual input but depend on and reflect also the
information acquired by other sensory modalities.},
file_url = {/fileadmin/user_upload/files/publications/dahl_kayser2010_6397[0].pdf},
web_url = {http://www.frontiersin.org/neuroscience/integrativeneuroscience/paper/10.3389/fnint.2010.00010/},
state = {published},
DOI = {10.3389/fnint.2010.00010},
author = {Dahl CD{dahl}{Department Human Perception, Cognition and Action}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ 6055,
title = {Functional magnetic resonance imaging of awake behaving macaques},
journal = {Methods},
year = {2010},
month = {3},
volume = {50},
number = {3},
pages = {178-188},
abstract = {In recent years, more and more laboratories have begun to develop fMRI for awake non-human primates. This research is essential to provide a link between non-invasive hemodynamic signals in the human brain and the vast body of knowledge gained from invasive electrophysiological studies in monkeys. Given that their brain structure is so closely related to that of humans and that monkeys can be trained to perform complicated behavioral tasks, results obtained with macaque fMRI and electrophysiology can be compared to fMRI results obtained in humans, thus providing information which is crucial to better understand the mechanisms by which different cortical areas perform their functions in the human brain. However, although the first publications on fMRI in awake behaving macaques appeared ten years ago [1], [2] and [3], relatively few laboratories perform such experiments routinely, a sign of the significant technical difficulties that must be overcome. The higher spatial resolution required because of the anima
l’s smaller brain results in poorer signal-to-noise ratios than in human fMRI, which is further compounded by problems due to animal motion. Here, we discuss the special challenges and benefits of fMRI in the awake monkey and review the methodologies and strategies for scanning behaving macaques.},
web_url = {http://www.sciencedirect.com/science?_ob=PdfDownloadURL&_uoikey=B6WN5-4X0F3VN-1&_tockey=%23toc%236953%239999%23999999999%2399999%23FLA%23&_orig=search&_acct=C000003178&_version=1&_userid=29041&md5=587179a4ac4bfa5bd95297e06bac1d},
state = {published},
DOI = {10.1016/j.ymeth.2009.08.003},
author = {Goense JBM{jozien}{Department Physiology of Cognitive Processes}, Whittingstall K{kevin}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ PanzeriBLK2010,
title = {Sensory neural codes using multiplexed temporal scales},
journal = {Trends in Neurosciences},
year = {2010},
month = {3},
volume = {33},
number = {3},
pages = {111-120},
abstract = {Determining how neuronal activity represents sensory information is central for understanding perception. Recent work shows that neural responses at different timescales can encode different stimulus attributes, resulting in a temporal multiplexing of sensory information. Multiplexing increases the encoding capacity of neural responses, enables disambiguation of stimuli that cannot be discriminated at a single response timescale, and makes sensory representations stable to the presence of variability in the sensory world. Thus, as we discuss here, temporal multiplexing could be a key strategy used by the brain to form an information-rich and stable representation of the environment.},
web_url = {http://www.sciencedirect.com/science?_ob=MiamiImageURL&_cid=271059&_user=29041&_pii=S0166223609002008&_check=y&_origin=&_coverDate=31-Mar-2010&view=c&wchp=dGLbVBA-zSkzV&md5=c5a95ac526738c217f417ef9f349f7b9/1-s2.0-S0166223609002008-main.pdf},
state = {published},
DOI = {10.1016/j.tins.2009.12.001},
author = {Panzeri S{stefano}, Brunel N, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ 6062,
title = {Improved neuronal tract-tracing with stable biocytin-derived neuroimaging agents},
journal = {ACS Chemical Neuroscience},
year = {2010},
month = {2},
volume = {1},
number = {2},
pages = {129-138},
abstract = {One of the main characteristics of brains is their profuse connectivity at different spatial scales. Understanding brain function evidently first requires a comprehensive description of neuronal anatomical connections. Not surprisingly a large number of histological markers were developed over the years that can be used for tracing mono- or polysynaptic connections. Biocytin is a classical neuroanatomical tracer commonly used to map brain connectivity. However, the endogenous degradation of the molecule by the action of biotinidase enzymes precludes its applicability in long-term experiments and limits the quality and completeness of the rendered connections. With the aim to improve the stability of this classical tracer, two novel biocytin-derived compounds were designed and synthesized. Here we present their greatly improved stability in biological tissue along with retained capacity to function as neuronal tracers. The experiments, 24 and 96 h postinjection, demonstrated that the newly synthesized molecule
s yielded more detailed and complete information about brain networks than that obtained with conventional biocytin. Preliminary results suggest that the reported molecular designs can be further diversified for use as multimodal tracers in combined MRI and optical or electron microscopy experiments.},
web_url = {http://pubs.acs.org/doi/pdf/10.1021/cn900010d},
state = {published},
DOI = {10.1021/cn900010d},
author = {Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Dhingra K{kirti}{Department Physiology of Cognitive Processes}, Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Canals S{canals}}
}

@Article{ 6148,
title = {Mapping of functional brain activity in freely behaving rats during voluntary running using manganese-enhanced MRI: Implication for longitudinal studies},
journal = {Neuroimage},
year = {2010},
month = {2},
volume = {49},
number = {3},
pages = {2544-2555},
web_url = {http://www.sciencedirect.com/science?_ob=PdfDownloadURL&_uoikey=B6WNP-4XM6K9C-1&_tockey=%23toc%236968%239999%23999999999%2399999%23FLA%23&_orig=search&_acct=C000003178&_version=1&_userid=29041&md5=3bf6091d834384671282cddb6fdb75},
state = {published},
DOI = {10.1016/j.neuroimage.2009.10.079},
author = {Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}, Canals S{canals}, Simanova I, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5939,
title = {Relationship of the BOLD signal with VEP for ultrashort duration visual stimuli (0.1 to 5 ms) in humans},
journal = {Journal of Cerebral Blood Flow and Metabolism},
year = {2010},
month = {2},
volume = {30},
number = {2},
pages = {449-458},
abstract = {There is currently a great interest to combine electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) to study brain function. Earlier studies have shown different EEG components to correlate well with the fMRI signal arguing for a complex relationship between both measurements. In this study, using separate EEG and fMRI measurements, we show that (1) 0.1 ms visual stimulation evokes detectable hemodynamic and visual-evoked potential (VEP) responses, (2) the negative VEP deflection at approx80 ms (N2) co-varies with stimulus duration/intensity such as with blood oxygenation level-dependent (BOLD) response; the positive deflection at approx120 ms (P2) does not, and (3) although the N2 VEP–BOLD relationship is approximately linear, deviation is evident at the limit of zero N2 VEP. The latter finding argues that, although EEG and fMRI measurements can co-vary, they reflect partially independent processes in the brain tissue. Finally, it is shown that the stimulus-induced impulse response
function (IRF) at 0.1 ms and the intrinsic IRF during rest have different temporal dynamics, possibly due to predominance of neuromodulation during rest as compared with neurotransmission during stimulation. These results extend earlier findings regarding VEP–BOLD coupling and highlight the component- and context-dependency of the relationship between evoked potentials and hemodynamic responses.},
web_url = {http://www.nature.com/jcbfm/journal/vaop/ncurrent/pdf/jcbfm2009224a.pdf},
state = {published},
DOI = {10.1038/jcbfm.2009.224},
author = {Yesilyurt B{baris}{Department High-Field Magnetic Resonance}, Whittingstall K{kevin}{Department Physiology of Cognitive Processes}, Ugurbil K, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Uludag K{kuludag}{Department High-Field Magnetic Resonance}}
}

@Article{ 6150,
title = {Stabilization of visual responses through cholinergic activation},
journal = {Neuroscience},
year = {2010},
month = {2},
volume = {165},
number = {3},
pages = {944-954},
abstract = {Neuronal processing of sensory information requires that rapidly changing synaptic inputs are continuously transformed into action potentials. Variability of spike firing is generally considered as noise and might therefore interfere with the reliability of synaptic transmission in sensory systems. In a system in which the number of spikes is a variable that determines the quality of neuronal transmission, variability of spike counts is a paradoxical attribute. In contrast, in a system in which precisely correlated spike firing can influence synaptic integration, response variability might be used as an additional mechanism for coding information. As acetylcholine has been shown to reduce spike-frequency adaptation and enhance gamma frequency (21-70 Hz) oscillations, we set out to study the influence of cholinergic modulation on the variability of spike counts and gamma oscillations. Iontophoretic application of carbachol, a cholinergic agonist, in cat primary visual cortex or electrical stimulation of the me
sencephalic reticular formation reduced the spike count variability and stabilized gamma frequency oscillations of visually induced responses. Response stabilization was correlated with enhancement of gamma-frequency oscillations but not with averaged firing rates. Lowering variability of sensory responses might be a mechanism to stabilize and improve reliability of neuronal transmission. Cholinergic activation may therefore influence the efficacy of neuronal transmission by modulating the precise timing of neuronal responses},
file_url = {/fileadmin/user_upload/files/publications/Rodriguez-Munk-2009-xxx_[0].pdf},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T0F-4XKXXV3-3-W&_cdi=4861&_user=29041&_pii=S0306452209017515&_orig=search&_coverDate=02%2F03%2F2010&_sk=998349996&view=c&wchp=dGLzVtb-zSkWz&md5=fd53ace3d23d471d17ec6764f0e4051e&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.neuroscience.2009.10.059},
author = {Rodriguez R, Kallenbach U, Singer W and Munk MHJ{munk}{Department Physiology of Cognitive Processes}}
}

@Article{ 6257,
title = {Decorrelated Neuronal Firing in Cortical Microcircuits},
journal = {Science},
year = {2010},
month = {1},
volume = {327},
number = {5965},
pages = {584-587},
abstract = {Correlated trial-to-trial variability in the activity of cortical neurons is thought to reflect the functional connectivity of the circuit. Many cortical areas are organized into functional columns, in which neurons are believed to be densely connected and to share common input. Numerous studies report a high degree of correlated variability between nearby cells. We developed chronically implanted multitetrode arrays offering unprecedented recording quality to reexamine this question in the primary visual cortex of awake macaques. We found that even nearby neurons with similar orientation tuning show virtually no correlated variability. Our findings suggest a refinement of current models of cortical microcircuit architecture and function: Either adjacent neurons share only a few percent of their inputs or, alternatively, their activity is actively decorrelated.},
web_url = {http://www.sciencemag.org/cgi/reprint/327/5965/584.pdf},
state = {published},
DOI = {10.1126/science.1179867},
author = {Ecker AS{aecker}{Research Group Computational Vision and Neuroscience}, Berens P{berens}{Research Group Computational Vision and Neuroscience}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Bethge M{mbethge}{Research Group Computational Vision and Neuroscience}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Tolias AS{atolias}{Department Physiology of Cognitive Processes}}
}

@Article{ 6268,
title = {Organic Memristor and Bio-Inspired Information Processing},
journal = {International Journal of Unconventional Computing},
year = {2010},
month = {1},
volume = {6},
number = {1},
pages = {15-32},
abstract = {The memristor is a circuit element whose conductance depends on its previous functioning history. Although postulated decades ago, it was actually fabricated only recently, spurring much debate and activity as to its possible applications in smart sensors and memory components in information handling systems. Recently we fabricated an organic memristor, basically a heterojunction between a conducting polymer (polyaniline) and a solid electrolyte (Li-doped polyethylene oxide). In this paper we describe the peculiar behavior of this device, due to the electrochemical control through ion flux and redox reactions in the conducting polymer, which lead to properties such as non linearity and memory. In special conditions, this organic memristor generates current auto-oscillation in fixed voltage conditions. Using these features we have fabricated several types of circuits which could be trained using the appropriate external stimuli, demonstrating supervised and unsupervised learning. Finally, the possibility of th
e formation of adaptive networks of statistically distributed self-assembled complex molecules for biologically inspired parallel information handling will be discussed.},
web_url = {http://www.oldcitypublishing.com/IJUC/IJUCabstracts/IJUC6.1abstracts/IJUCv6n1p15-32Erokhin.html},
state = {published},
author = {Erokhin V, Sch\"uz A{schuez}{Department Physiology of Cognitive Processes} and Fontana MP}
}

@Article{ 6158,
title = {Visual enhancement of the information representation in auditory cortex},
journal = {Current Biology},
year = {2010},
month = {1},
volume = {20},
number = {1},
pages = {19-24},
abstract = {Combining information across different sensory modalities can greatly facilitate our ability to detect, discriminate, or recognize sensory stimuli [1] and [2]. Although this process of sensory integration has usually been attributed to classical association cortices, recent work has demonstrated that neuronal activity in early sensory cortices can also be influenced by cross-modal inputs [3], [4] and [5]. Here we demonstrate that such “early” multisensory influences enhance the information carried by neurons about multisensory stimuli. By recording in auditory cortex of alert monkeys watching naturalistic audiovisual stimuli, we quantified the effect of visual influences on the trial-to-trial response variability and on the amount of information carried by neural responses. We found that firing rates and precisely timed spike patterns of individual units became more reliable across trials and time when multisensory stimuli were presented, leading to greater encoded stimulus information. Importantly, this mu
ltisensory information enhancement was much reduced when the visual stimulus did not match the sound. These results demonstrate that multisensory influences enhance information processing already at early stages in cortex, suggesting that sensory integration is a distributed process, commencing in lower sensory areas and continuing in higher association cortices.},
web_url = {http://download.cell.com/current-biology/pdf/PIIS096098220901940X.pdf},
state = {published},
DOI = {10.1016/j.cub.2009.10.068},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Inbook{ GoenseL2010,
title = {Physiological basis of the BOLD signal},
year = {2010},
month = {5},
pages = {21-46},
abstract = {Functional magnetic resonance imaging (fMRI) and other non-invasive imaging methods have greatly expanded our knowledge of human brain function. Although MRI was invented in the early 1970s and has been used clinically since the mid-1980s, its use in cognitive neuroscience expanded greatly with the advent of blood oxygenation level dependent (BOLD) functional imaging, and by now, fMRI is a mainstay of neuroscience research. This chapter gives an overview of the relation between the BOLD signal and the underlying neural signals. It focuses on intracortically recorded neural signals, recorded with microelectrodes.},
web_url = {http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195372731.001.0001/acprof-9780195372731-chapter-2},
editor = {Ullsperger, M. , S. Debener},
publisher = {Oxford University Press},
address = {Oxford},
booktitle = {Simultaneous EEG and fMRI: recording, analysis, and application},
state = {published},
ISBN = {978-0-19-537273-1},
DOI = {10.1093/acprof:oso/9780195372731.003.0002},
author = {Goense J{jozien}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Inbook{ 6029,
title = {Imaging Cross-Modal Influences in Auditory Cortex},
year = {2010},
month = {4},
volume = {2},
pages = {123-137},
abstract = {Recent studies have made considerable progress in understanding how our brain combines the information from different sensory modalities and much evidence about the cortical regions involved has been provided by functional magnetic resonance imaging. Imaging studies have, for example, shown that cross-modal influences occur already at early stages of auditory cortex. However, given our still limited understanding of the functional organization of human auditory cortex, these results are often to interpret with respect to the exact localization of cross-modal influences. Here we discuss a localization technique, which provides a functional map of individual fields in the auditory cortex of individual subjects. Using high-resolution imaging techniques in an animal model with known organization of auditory cortex, we proved the feasibility of this functional mapping technique and demonstrated its use in localizing cross-modal influences to individual auditory fields. Our results show that cross-modal influences
already occur in secondary auditory cortices and increase along the auditory processing hierarchy. While these results provide good evidence that auditory processing can be affected by non-acoustic stimuli very early on, we also discuss the interpretability of these findings with regard to the underlying neuronal activity, which is considerable hampered by the still unknown neural basis of the fMRI signal.},
web_url = {http://www.springerlink.com/content/q5jv37h027525450/},
editor = {Kaiser, J. , M. J. Naumer},
publisher = {Springer},
address = {New York, NY, USA},
booktitle = {Multisensory Object Perception in the Primate Brain},
state = {published},
ISBN = {978-1-441-95614-9},
DOI = {10.1007/978-1-4419-5615-6_8},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Petkov C{chrisp} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Inbook{ 5639,
title = {The Electrophysiological Background of the fMRI Signal},
year = {2010},
month = {1},
pages = {23-33},
abstract = {The ability to non-invasively study the architecture and function of the human brain constitutes one of the most exciting cornerstones for modern medicine, psychology and neuroscience. Current in vivo imaging techniques not only provide clinically essential information and allow new forms of treatment, but also reveal insights into the mechanisms behind brain function and malfunction. This supremacy of modern imaging rests on its ability to study the structural properties of the nervous system simultaneously with the functional changes related to neuronal activity. As a result, imaging allows us to combine information about the spatial organization and connectivity of the nervous system with information about the underlying neuronal processes and provides the only means to link perception and cognition with the neural substrates in the human brain.},
web_url = {http://www.springerlink.com/content/kv37199865565428/},
editor = {Ulmer, S. , O. Jansen},
publisher = {Springer},
address = {Berlin, Germany},
booktitle = {fMRI:Basics and Clinical Applications},
state = {published},
ISBN = {978-3-540-68131-1},
DOI = {10.1007/978-3-540-68132-8_4},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Inbook{ Bartels2010,
title = {Die Liebe im Kopf: Über Partnerwahl, Bindung und Blindheit},
year = {2010},
pages = {76-106},
web_url = {http://www.schattauer.de/shop/product_info.php/info/p503_.html/XTCsid/060bdefc431db8345d3b43ba8048bc29},
editor = {Spitzer, M. , W. Bertram},
publisher = {Schattauer},
address = {Stuttgart, Germany},
booktitle = {Hirnforschung für Neu(ro)gierige: Braintertainment 2.0},
state = {published},
ISBN = {978-3-7945-2736-6},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Inbook{ PanzeriMNMP2010,
title = {Population Coding},
year = {2010},
pages = {303-319},
abstract = {Population coding is the quantitative study of which algorithms or representations are used by the brain to combine together and evaluate the messages carried by different neurons. Here, we review an information-theory-based approach to population coding. We discuss how to quantify the information carried by a neural population and how to quantify the contribution of individual members of the population, or the interaction between them, to the overall information encoded by the considered group of neurons. We present examples of applications of this formalism to simultaneous recordings of multiple spike trains.},
web_url = {http://www.springerlink.com/content/978-1-4419-5674-3/contents/},
editor = {Grün, S. , S. Rotter},
publisher = {Springer},
address = {New York, NY, USA},
series = {Springer series in computational neuroscience ; 7},
booktitle = {Analysis of Parallel Spike Trains},
state = {published},
ISBN = {978-1-4419-5675-0},
DOI = {10.1007/978-1-4419-5675-0_14},
author = {Panzeri S{stefano}, Montani F, Notaro G, Magri C{cmagri}{Department Physiology of Cognitive Processes} and Peterson RS}
}

@Poster{ 7068,
title = {"Own-species" bias in the categorical representation of a human/monkey continuum in the human and non-human primate temporal lobe},
year = {2010},
month = {11},
volume = {40},
number = {581.20},
abstract = {While face categorization is a fundamental cognitive ability of human and non-human primates, its neural basis remain poorly understood. Using a new morphing technique, we created realistic three-dimensional morphed faces that linearly span the continuum between humans and monkeys (“species” continuum). Extensive categorization and discrimination experiments in human observers show that humans perceive the “species” continuum categorically. Moreover, the position of the categorical boundary is shifted from the center towards the human end of the continuum, suggesting a higher sensitivity to changes near the own-species prototype. We presented a subset of these faces to human subjects in a block-design fMRI experiment to record BOLD signals from the temporal lobe while participants performed an unrelated task at fixation. We applied a multivariate approach based on (Pearson) correlations to compute the difference between activity patterns elicited by faces along the continuum. Using this method, we looked for a categorical representation in face selective areas previously defined using an independent, standard "Face-localizer" experiment. Consistent with the psychophysical results, we found a categorical response with a bias towards the human end of the stimulus continuum in the activation patterns of the left human STS. In addition, activation in human ventral temporal cortex was most sensitive to deviations from the human prototype. To look for similar effects in monkeys, we applied an equivalent multivariate approach to analyze extracellular signals from a population of neurons recorded from the STS of two macaque monkeys while they fixated at the same type of faces. Additionally, the position of the perceptual category boundary was determined with a preferential-looking-time experiment. In both behavioral and neuronal monkey data, we found a categorical representation of the continuum, but in this case, with a bias towards the monkey end of the continuum. Our results demonstrate the neural basis of categorical representation of a facial attribute in the human and non-human primate brain. Together, our findings suggest that experience can lead to significant shifts in category boundary for face stimuli.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Sigala Alanis GR{sigala}{Department Physiology of Cognitive Processes}, Schultz J{johannes}{Department Human Perception, Cognition and Action}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ 7069,
title = {A cortical map of vestibular representation in the rodent brain revealed by functional imaging and electrophysiology},
year = {2010},
month = {11},
volume = {40},
number = {583.11},
abstract = {The vestibular system is important for balance and spatial navigation. It has perhaps more influence on central processing than any other sensory modality, impacting on visual, auditory, motor and even cognitive function. Though several primate studies implicate vestibular modulation of neural activity in visual areas, there is almost nothing known about where and how vestibular information may be integrated at the level of the cortex. As a first step to explore vestibular integration across sensory-motor cortical areas we used electrical stimulation of the vestibular nerve in Lister Hooded rats (~300 g, anesthetized with urethane 1.2 - 1.4 g/kg) together with fMRI and extracellular field and multiunit recordings to establish the first cortical maps of vestibular representation.
Electrical stimulation of the VN was confirmed using vestibulo-ocular responses (evoked eye movements). The DC current threshold to elicit this reflex was 296 ± 36 µA (n = 11 rats). Using a train of biphasic pulses at different frequencies, stimulation at 333 Hz had the lowest threshold (206 ± 41 µA, n = 7 rats) and was used for all subsequent experiments. Once VN stimulation was established, rats were placed in a 7T small-animal scanner (Bruker) and the functional connectivity of the VN was mapped with electric stimulation driven fMRI as previously described (Canals et al. 2009 Curr Biol 19:398-403). Functional MRI data were analyzed offline with our own software developed in MATLAB and including the statistical parametric mapping packages (SPM2). After linear detrending, temporal filtering (0.015-0.2 Hz) and spatial filtering (3 x 3 Gaussian kernel of 1.5 sigma) of voxel time series, general linear model analysis was applied with a boxcar convolved with a gamma probability-density function to account for the hemodynamic delay in the BOLD signal.
Our results show evoked activity in vestibular brainstem nuclei, vestibular cerebellum, anterior thalamus and multiple higher-order areas, including limbic, motor, and sensory cortices including parietal. In a second group of animals, extracellular recordings using silicone probes from some of the above identified areas such as retrosplenial and somatosensory and motor cortices we identified short latency evoked field potentials and long lasting increases in multiunit firing rates.
We therefore suggest that vestibular signaling occurs in several prominent limbic and sensory-motor cortical regions and that the integration of such signals warrants further investigation.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Rancz EA, Canals SG{canals}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Brichta AM and Margrie TW}
}

@Poster{ 7064,
title = {Assessing the spatio-temporal dynamics of visual receptive fields by fMRI},
year = {2010},
month = {11},
volume = {40},
number = {371.6},
abstract = {A fundamental problem of neuroscience is being able to understand the input-output relationship of early sensory areas. Central to this understanding is the notion of the receptive field (RF). Previous electrophysiological studies in the visual system of primates have demonstrated that receptive fields do not have fixed properties but are dynamically changing as a function of the stimulation conditions or behavioral tasks. In the human, aggregate (voxel-based) receptive field sizes (pRF) of early visual cortex were estimated by fMRI using standard retinotopic stimuli (Dumoulin SO, Wandell BA, Population receptive field estimates in human visual cortex, Neuroimage 39, 2008) but it would be desirable to obtain more detailed estimates of RF spatio-temporal properties. In this study, we have used flickering checkerboard stimuli (white noise) in order to measure the spatio-temporal response properties of population RFs by fMRI. Blood oxygen level dependent (BOLD) measurements were performed both in anesthetized macaques (4.7 Tesla vertical scanner) and awake-fixating human subjects (3 Tesla Siemens Trio). We found that the BOLD-signal amplitude in early visual cortex changes as a function of the checker-size of the stimulus and this can provide estimates of the central excitatory integration area as well as the surround suppression of the aggregate RFs. The estimates of the size of the central portion of the RFs were found to increase with eccentricity within each visual area as well as from lower to higher visual areas. The results were comparable to pRF-size estimates derived from additional experiments with classical retinotopic stimuli (expanding rings, rotating wedges, moving horizontal and vertical bars). Current work focuses on evaluating how RF parameter estimates change as a function of the temporal frequency and contrast of the stimuli. We believe that this method can provide robust estimates of RF parameters which can be used in longitudinal studies for the assessment of cortical reorganization and plasticity in patients suffering from retinal and cortical lesions.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Keliris GA{george}{Department Physiology of Cognitive Processes}, Shao Y{yshao}{Department Physiology of Cognitive Processes}, Papanikolaou A{amalia}{Department Physiology of Cognitive Processes}, Peng X, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Smirnakis SM{stelios}}
}

@Poster{ FrankeNMHPLEMO2010,
title = {Automated positioning of extracellular multi electrodes for online spike sorting},
year = {2010},
month = {11},
volume = {40},
number = {616.10},
abstract = {Extracellular recordings are a key tool to study the activity of neurons in vivo. Especially in the case of experiments with behaving animals, however, the tedious procedure of electrode placement can take a considerable amount of expensive and restricted experimental time. Furthermore, due to tissue drifts and other sources of variability in the recording setup, the position of the electrodes with respect to the neurons under study can change, causing low recording quality. Here, we developed a system for automatic electrode placement and its evaluation. The main features of this study are:
First, we introduce a quality measure for the recording position of the electrode which should be maximized during recordings and is particularly suitable for the use of multi-trodes, e.g. tetrodes. This quality measure is based on the detected spike waveforms only and does not rely on computationally expensive clustering or spike sorting. It is also invariant for the discharge rate of the neurons.
Second, an automated positioning system based on this quality measure is proposed. It estimates the recording quality at the current recording position. It is able to find favorable recording positions by locally maximizing the quality measure and adopts the electrode position smoothly to changes of the neuron positions. If the quality decreases, it will either try to maximize the quality by accounting for the changes in neuron positions or to find a new recording position where action potentials can be measured with a high signal to noise ratio.
Third, we evaluate the system using a new simulator for extracellular recordings based on realistically reconstructed 3D neurons. The shape of the extracellular waveform is estimated from their morphology for every point on a 3D grid around the neurons. If a recording device is close to a neuron, the corresponding waveform for its spikes is calculated from that grid by interpolating the waveforms of the adjacent grid positions. This way we can simulate a realistic recording environment in which an unconstrained movement of electrodes and neurons and an interaction with the positioning system is possible.},
web_url = {http://www.sfn.org/am2010/},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA.},
state = {published},
author = {Franke F{ffranke}{Department Physiology of Cognitive Processes}, Natora M, Meier P, Hagen E, Petersen KH, Linden H, Einevoll GT, Munk M{munk}{Department Physiology of Cognitive Processes} and Obermayer KH}
}

@Poster{ 7071,
title = {Comparing concentration levels of multiple neurochemically active compounds in blood and brain tissue of non-human primates by using dual microdialysis sampling and capillary hydrophilic interaction chromatography-mass s pectrometry},
year = {2010},
month = {11},
volume = {40},
number = {648.9},
abstract = {Proper brain function is tightly controlled by neurochemically active compounds (NACs). These NACs can be directly detected in the brain. However the actual NACs and their metabolites can also be monitored in the blood. Measuring the concentrations and ratios of NACs simultaneously collected in the blood and brain can therefore provide important insights in their intracortical release and metabolism. This will allow interpolation of brain NACs concentrations/ratios from systemically sampled NACs concentrations (blood), which can serve as biomarker for dysfunctional processes in the brain.
We report here a method for the simultaneous neurochemical analysis of five polar compounds, acetylcholine, lactate, pyruvate, glutamine and glutamate. We sampled these NACs from venous blood as well as intracortically from the primary visual cortex of anesthetized non-human primates during visual stimulation.
Simultaneous systemic and intracortical microdialysis was used for sample collection. Great care was taken to synchronize to two sampling devices and to adjust the sample preparation for direct comparability. After sample collection we used a capillary hydrophilic interaction liquid chromatography (HILIC) for optimal separation of the sample’s components. For detection of the NACs tandem mass spectrometry (MS/MS) was coupled to HILIC without using any additional chemical treatment. The detection limit of acetylcholine, lactate, pyruvate, glutamine and glutamate was 45 amol, 0.9 pmol, 0.6 pmol, 1.5 fmol and 15 fmol, respectively.
Our results demonstrate that we can reliably and simultaneously quantify the concentrations of these five compounds in brain and blood microdialysate from non-human primates. The concentration of all tested NACs was higher in the blood compared to the brain tissue (p<0.05). Blood and brain values were in agreement with the Human Metabolome Database Version 2.5 which we used since corresponding non-human primate data are not available. We can now compare the different ratios of the sampled NACs and test for specific changes under pharmacological interventions mimicking dysfunctional states of brain function.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Li J{juan}{Department Physiology of Cognitive Processes}, von Pf\"ostl V{vpfoestl}{Department Physiology of Cognitive Processes}, Zaldivar D{dzaldivar}{Department Physiology of Cognitive Processes}, Zhang X{xiaozhe}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rauch A{arauch}{Department Physiology of Cognitive Processes}}
}

@Poster{ 7067,
title = {Cross-frequency coupling of neural signals within and between early visual areas V1 and V2},
year = {2010},
month = {11},
volume = {40},
number = {553.13},
abstract = {Recently, it was shown that the power of high frequency bands like gamma (>40 Hz) or spiking rate of cortical neurons is modulated by the phase of low frequency bands (especially delta 1-4Hz) - referred to as cross-frequency coupling (CFC). CFC has been shown in wakefulness and under anesthesia during either spontaneous activity or sensory stimulation; and might play an important role in sensory processing and influencing information flow in brain. Here we studied CFC within and between early visual areas V1 and V2 in three anesthetized monkeys (Macaca mulatta). We simultaneously recorded spontaneous activities from 2+2 electrodes localized in V1 and V2 respectively. The signals were filtered into delta (1-4 Hz), low-gamma (20-60 Hz), gamma (65-120 Hz), high-gamma (125-300 Hz) and multiple unit activity (MUA) (900-3200 Hz). The amplitude envelop for low-gamma, gamma, high-gamma and MUA, along with the instantaneous phase [-π, π] for the delta band were extracted using the Hilbert transform. CFC between delta-phase and the amplitude of low-gamma, gamma, high-gamma and MUA was first calculated separately for V1 and V2, and then between V1 and V2 (e.g. comparing the phase of V1 with the power of V2). We found significant CFC in V1 and V2, as well as between V1 and V2. While there were no differences in CFC within the same areas, we observed differences in CFC between the various frequency bands studied and between different areas. Generally the peak for the low-gamma amplitude fell onto the rising phase of the delta oscillation, while the amplitude of the gamma band peaked during the negative slope of the delta phase. The amplitude for high-gamma and MUA peaked when delta was in its negative trough (0 phase). Interestingly, while the preferred phase for intra-area CFC was always around zero, combining the delta phase from either V1 or V2 with the amplitude of the high frequency signals from either V2 or V1 revealed a different picture. When taking the delta phase from V1, the preferred phase of the amplitude of high frequency signals from V2 fell onto the rising phase of the delta oscillation; however, when the delta phase came from V2, the amplitudes of the high frequency bands in V1 peaked during the negative slope of the delta oscillation. Our data suggest that CFC is a general property of the early visual areas, and that different profiles of inter-area CFC might reflect feed forward and feedback processing between cortical areas.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Schridde U{schridde}{Department Physiology of Cognitive Processes}, Whittingstall K{kevin}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 7055,
title = {Decorrelated neuronal firing in cortical microcircuits},
year = {2010},
month = {11},
volume = {40},
number = {73.20},
abstract = {Correlated trial-to-trial variability in the activity of cortical neurons is thought to reflect the functional connectivity of the circuit. Many cortical areas are organized into functional columns, in which neurons are believed to be densely connected and share common input. Numerous studies report a high degree of correlated variability between nearby cells. We developed chronically implanted multi-tetrode arrays offering unprecedented recording quality to re-examine this question in primary visual cortex of awake macaques. We found that even nearby neurons with similar orientation tuning show virtually no correlated variability.
In a total of 46 recording sessions from two monkeys, we presented either static or drifting sine-wave gratings at eight different orientations. We recorded from 407 well isolated, visually responsive and orientation-tuned neurons, resulting in 1907 simultaneously recorded pairs of neurons. In 406 of these pairs both neurons were recorded by the same tetrode.
Despite being physically close to each other and having highly overlapping receptive fields, neurons recorded from the same tetrode had exceedingly low spike count correlations (rsc = 0.005 ± 0.004; mean ± SEM). Even cells with similar preferred orientations (rsignal > 0.5) had very weak correlations (rsc = 0.028 ± 0.010). This was also true if pairs were strongly driven by gratings with orientations close to the cells’ preferred orientations.
Correlations between neurons recorded by different tetrodes showed a similar pattern. They were low on average (rsc = 0.010 ± 0.002) with a weak relation between tuning similarity and spike count correlations (two-sample t test, rsignal < 0.5 versus rsignal > 0.5: P = 0.003, n = 1907).
To investigate whether low correlations also occur under more naturalistic stimulus conditions, we presented natural images to one of the monkeys. The average rsc was close to zero (rsc = 0.001 ± 0.005, n = 329) with no relation between receptive field overlap and spike count correlations. We obtained a similar result during stimulation with moving bars in a third monkey (rsc = 0.014 ± 0.011, n = 56).
Our findings suggest a refinement of current models of cortical microcircuit architecture and function: either adjacent neurons share only a few percent of their inputs or, alternatively, their activity is actively decorrelated.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Ecker AS{aecker}{Research Group Computational Vision and Neuroscience}, Berens P{berens}{Research Group Computational Vision and Neuroscience}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Bethge M{mbethge}{Research Group Computational Vision and Neuroscience}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Tolias AS{atolias}{Department Physiology of Cognitive Processes}}
}

@Poster{ 7072,
title = {Effects of lactate on primary visual cortex of non-human primates investigated by pharmaco mri and neurochemical analysis},
year = {2010},
month = {11},
volume = {40},
number = {648.15},
abstract = {Lactate is a common metabolic product of anaerobic glucose metabolism. It can freely pass the blood brain barrier and it’s known to play also an important role in brain metabolism. We used pharmaco MRI and tested the effect of systemic lactate application on the BOLD signal in primary visual cortex (V1) of anesthetized non-human primates during visual stimulation. We also monitored the pharmacokinetics of the applied lactate in the blood using microdialysis and HPLC (high performance liquid chromatography) coupled to MS/MS (mass spectrometry). The lactate pharmacokinetics allows us to investigate the actual plasma concentrations of lactate, and thus, how this correlates to changes in the BOLD signal.
After lactate infusion of 0.6 mmol/kg, we observed two consistent effects in the BOLD signal: An initial decrease in visually-induced modulation followed by a subsequent positive baseline shift (n = 10, p < 0.05). The plasma lactate levels significantly increased approximately 9 minutes after systemic application and were correlated with the positive baseline shift in the BOLD signal (p < 0.05). This is in line with a lactate-induced increase of CBF in sensory stimulated regions observed in earlier studies. However, the onsets of lactate increases were late - thereby indicating a lactate buffering mechanism. This could be due to an uptake of lactate by erythrocytes buffering lactate until this capacity is saturated, and plasma levels start to rise with some delay. We conclude that the positive baseline shift in the BOLD signal is triggered by a rise in CBF due to increased plasma lactate. Interestingly, during the observed decrease in visual modulation, (though lactate was already being applied), the lactate levels in the blood were still comparable to the pre-injection concentrations (p < 0.05). How this lactate uptake by erythrocytes influences the BOLD signal has to be further investigated. Nonetheless, our results reveal a complex interaction of lactate in the brain which was only detectable by using pharmaco MRI in combination with neurochemical monitoring of lactate.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {von Pf\"ostl V{vpfoestl}{Department Physiology of Cognitive Processes}, Li J{juan}{Department Physiology of Cognitive Processes}, Zaldivar D{dzaldivar}{Department Physiology of Cognitive Processes}, Goense J{jozien}{Department Physiology of Cognitive Processes}, Zhang X{xiaozhe}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rauch A{arauch}{Department Physiology of Cognitive Processes}}
}

@Poster{ 7056,
title = {Evidence for predictive coding in early visual cortex in context of self-induced visual motion},
year = {2010},
month = {11},
volume = {40},
number = {74.11},
abstract = {The model of “predictive coding” suggests that feedback from a higher- to a lower-order visual area carries predictions of lower-level neural activities, whereas the feedforward connections carry the residual errors between the predictions and the actual lower-level activities (Rao and Ballard, 1999). We tested this theory in context of processing of planar motion in early (foveal) visual cortex. In a 2x2 factorial design, human subjects either fixated (eyes still) or carried out smooth pursuit on a display containing a planar random dot-field that was either stationary or moving coherently in-plane. This led to four conditions: (a) fixation on static dot-field, (b) fixation on moving dot-field, (c) pursuit on static dot-field, (d) pursuit of moving dot-field (pursuit was locked to the dot-motion). Neural activity was measured using fMRI at 3T.
If early visual cortex coded for retinal motion, (b) and (c) would be expected to activate early visual cortex equally, and more than (a) and (d). In contrast, predictive coding would result in different responses. In addition to the above, early visual cortex would also code the error signal for mismatches between retinal motion input and the prediction for retinal motion, based on e.g. pursuit-related efferent copies. Such mismatches between prediction and input would occur in (b) (retinal motion without prediction of it) and in (d) (absence of retinal motion despite prediction of it). Note that these mismatches are equivalent to the presence of objective motion in the display. Thus, predictive coding would lead to highest responses in (b) (error + input), medium responses in (c) (input only) and (d) (error only), and lowest response in (a).
We found (across the whole brain) the only activity satisfying these criteria in the occipital poles. The occipital poles contain the foveal confluence of early visual areas V1-V3, and are thus the key candidate for the above hypothesis. Their responses matched the hypothesized pattern precisely. In contrast, activity in motion responsive areas such as V5/MT+ and parietal regions was mainly driven by eye-movements and by retinal motion. Offline eye-tracking revealed that our results cannot be explained by differential fixation accuracies across conditions. It remains to be elucidated whether predictive coding actually accounts for the results, or whether direct feedback of objective motion signals from higher-level areas sums up with retinal input to the response observed in the occipital pole. Nevertheless, our results let us conclude that activity in the foveal representation of the early visual cortex fully match the predictions of Rao and Ballard (1999) for predictive coding.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Fischer E{efischer}{Department Physiology of Cognitive Processes}, B\"ulthoff HH{hhb}{Department Human Perception, Cognition and Action}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ 7046,
title = {High frequency phase-spike synchronization of extracellular signals modulates causal interactions in monkey primary visual cortex},
year = {2010},
month = {11},
volume = {40},
number = {616.2},
abstract = {Functional correlates of Rhythms in the gamma band (30-100Hz) are observed in the mammalian brain with a large variety of functional correlates. Nevertheless, their functional role is still debated. One way to disentangle this issue is to go beyond usual correlation analysis and apply causality measures that quantify the directed interactions between the gamma rhythms and other aspects of neural activity. These measures can be further compared with other aspects of neurophysicological signals to find markers of neural interactions.
In a recent study, we analyzed extracellular recordings in the primary visual cortex of 4 anesthetized macaques during the presentation of movie stimuli using a causality measure named Transfer Entropy. We found causal interactions between high frequency gamma rhythms (60-100Hz) recorded in different electrodes, involving in particular their phase, and between the gamma phase and spiking activity quantified by the instantaneous envelope of the MUA band (1-3kHz).
Here, we further investigate in the same dataset the meaning of these phase-MUA and phase-phase causal interactions by studying the distribution of phases at multiple recording sites at lags around the occurrence of spiking events.
First, we found a sharpening of the gamma phase distribution in one electrode when spikes are occurring in other recording site. This phenomena appeared as a form of phase-spike synchronization and was quantified by an information theoretic measure. We found this measure correlates significantly with phase-MUA causal interactions. Additionally, we quantified in a similar way the interplay between spiking and the phase difference between two recording sites (reflecting the well-know concept of phase synchronization). We found that, depending on the couple of recording site, spiking can correlate either with a phase synchronization or with a desynchronization with respect to the baseline. This effect correlates very well with the phase-phase causality measure.
These results provide evidence for high frequency phase-spike synchronization to reflect communication between distant neural populations in V1. Conversely, both phase synchronization or desynchronization may favor neural communication between recording sites. This new result, which contrasts with current hypothesis on the role of phase synchronization, could be interpreted as the presence of inhibitory interactions that are suppressed by desynchronization. Finally, our findings give new insights into the role of gamma rhythms in regulating local computation in the visual cortex.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Besserve M{besserve}{Department Empirical Inference}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Sch\"olkopf B{bs}{Department Empirical Inference}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Poster{ 7060,
title = {Interplay of visually-evoked and saccade-evoked activity in the primate superior temporal lobe},
year = {2010},
month = {11},
volume = {40},
number = {280.21},
abstract = {Saccadic eye movements (SEMs) are the primary means of actively sampling the visual environment. The effect of saccadic eye movements on the neural processing of visual information has been characterized for retinotopic cortex [1,2], primarily in the forms of saccadic suppression [3]. Whereas previous studies have provided evidence for SEM-related activity in higher-order areas such as IT [4] and the hippocampus [5], we know of no investigation of neural activity in the STS, a region anatomically and functionally implicated in eye movements.
To address this issue, we analyzed local field potential (LFP) data recorded from the upper bank superior temporal sulcus (uSTS) of two awake rhesus macaques passively viewing images of faces and non-face objects. As expected, LFP phase and amplitude in different frequency bands were modulated relative to image onset (i.e. image-evoked responses). In addition, responses were modulated relative to fixation onset, and varied based on the delay between image onset and fixation onset, suggesting an interaction between visual-evoked and SEM-evoked responses. To determine whether ‘well-timed’ fixations would lead to greater phase-locking of the evoked response [1] we selected trials in which a fixation was made within 20 ms of image onset (quasi- ‘active vision' condition), and compared responses to trials in which no eye movements were made in the interval -150 to 200 ms relative to image onset ('passive vision' condition). Phase concentration was increased in the alpha and beta frequency bands around the onset time of image-evoked responses in the active compared to passive conditions. In addition, the mean phase across electrode sites became more consistent, resulting in a larger-amplitude population evoked response for active than passive conditions.
Our results demonstrate an interaction of sensory and saccadic signals in higher-order visual areas. The modulation observed is consistent with a role for active vision in reducing neural variability, enhancing signal transmission along visual pathways.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Bartlett AM, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Hoffman KL{kari}{Department Physiology of Cognitive Processes}}
}

@Poster{ 7061,
title = {Population coding in auditory cortex - time scales and intrinsic reference frames},
year = {2010},
month = {11},
volume = {40},
number = {324.12},
abstract = {Natural sounds such as communication signals and music are composed of complex temporal features that cover a wide range of time scales. Our auditory system excels at resolving this temporal structure and temporal features are crucial for identifying sound qualities and understanding speech. Yet, how auditory cortex neurons encode rapid sound features remains a matter of investigation.
To shed light on this issue we recorded the activity of neural populations in caudal auditory cortex of alert macaque monkeys during stimulation with a rapid sequence of synthetic random chords and with naturalistic stimuli. We quantified stimulus discriminability by means of both decoding and information theoretic measures. We used these data to investigate two important questions related to temporal coding in auditory cortex: 1) What is the time scale at which spike patterns of auditory cortex neurons carry sensory information? And 2) is it possible to ‘read’ such temporal activity patterns without having exact knowledge about external stimulus timing?
With regard to the first question we find that auditory cortex responses are very precise and can encode stimulus information in spike patterns at the millisecond scale. Importantly, we find that ‘reading’ responses at precisions coarser than 4ms causes a significant loss in the information, which reaches already 10% at an effective precisions of 6ms. This information loss induced by ignoring millisecond precise spike patterns was more prominent during stimulation with random chords, but for a subset of neurons also prevailed during stimulation with natural sounds.
With regard to the second question we find that one can detect the timing of stimulus onset directly from the population of neural responses with a precision of about 8ms. This population derived timing defines an internal reference frame that can be used for temporal response decoding without making reference to an external clock. Quantifying the information lost by using internal rather than external reference frames suggests that the auditory system can well achieve fine temporal stimulus encoding even without precise knowledge about external stimulus timing.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Poster{ 7065,
title = {Population receptive field mapping in a macaque monkey with macular degeneration},
year = {2010},
month = {11},
volume = {40},
number = {371.7},
abstract = {Macular degeneration (MD) is a common cause of human visual impairment. Typically MD deprives the foveal part of the primary visual cortex from retinal input. It has been reported that visual areas undergo extensive plastic reorganization in response to such deprivation (Baker et al., J. Neurosci. 2005), but this question remains not conclusively settled.
We used 4.7 Tesla functional magnetic resonance imaging (fMRI) to study the visual cortex of an adult macaque monkey with binocular central retinal lesions due to a form of juvenile MD. FMRI experiments were performed under light remifentanyl induced anesthesia. Standard moving horizontal/vertical bar stimuli were presented to the subject and the population receptive field (RF) method (Dumoulin and Wandell, Neuroimage 2008) was used to measure retinotopic maps and population receptive field sizes in early visual areas. RF size was plotted as a function of eccentricity in early visual areas. As expected, population based RFs increase in size as a function of eccentricity within each visual area, and as we move from lower to higher visual areas at a fixed eccentricity. In general, there is good agreement between maps obtained by fMRI and previous results obtained by anatomical and physiological methods.
The pattern of activity elicited in the MD monkey was compared to the pattern of activity elicited in two control monkeys. The primary visual cortex of the MD animal shows an extensive area devoid of BOLD (blood oxygen level dependent) activity that includes the fovea and roughly corresponds to the expected size of the retinal lesion projection zone (LPZ). Visually driven activity starts beyond the border of the calcarine sulcus, at approximately 9 degrees eccentricity a distance of ~ 36 mm from foveal V1 in this animal. RF size maps derived from non-deafferented cortex abutting the retinal LPZ were comparable to RF size maps derived from the corresponding area in control subjects. Further investigation using fMRI and standard electrophysiology methods is in progress.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Shao Y{yshao}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Papanikolaou A{amalia}{Department Physiology of Cognitive Processes}, Fischer DM, Nagy D, J\"agle H, Seeliger MW, Augath M{mark}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Smirnakis SM{stelios}}
}

@Poster{ 7063,
title = {Population receptive field mapping in human subjects with visual cortical lesions},
year = {2010},
month = {11},
volume = {40},
number = {371.5},
abstract = {Damage to the primary visual cortex (V1) as a result of stroke or other brain diseases can lead to a loss of conscious vision in the contralateral visual hemifield. Cortical blindness affects many activities on a patient's daily life and is considered to be a heavy burden while there are few, if any, options for rehabilitation and recovery. A much debated issue is whether the visual cortex is able to reorganize after injury in adult human subjects, and if so, what may be the mechanism of reorganization. Here we apply an important new approach introduced by Dumoulin and Wandell (Doumoulin SO, Wandell BA, Population receptive field estimates in human visual cortex, Neuroimage 39, 2008), which uses functional magnetic resonance imaging (fMRI) to measure the aggregate receptive field properties of neuronal populations voxel by voxel in the visual cortex. The purpose of this study is to compare receptive field measurements in patients with cortical lesions with controls and to investigate whether these measurements change following injury. Patients were fixating in the magnet and fMRI measurements were obtained during the presentation of standard visual stimuli used in retinotopic mapping (rotating wedges, expanding rings, horizontally and vertically moving bars). The patient’s intact hemisphere, as well as normal subjects were used as controls. In some controls an area of the stimulus was obscured (“artificial scotoma”) to simulate as much as possible the real scotoma of the patients. Preliminary results suggest that receptive field measurements obtained in patients and in subjects examined under the artificial scotoma condition differ from measurements obtained in controls under the normal visual stimulation condition. We are in the process of obtaining further control tests and measurements to confirm these findings and to assess to what degree they correspond to cortical reorganization. Future research will focus on using these methods to study the capacity of various visual rehabilitation training methods to induce visual cortex reorganization.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Papanikolaou A{amalia}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Peng X, Shao Y{yshao}{Department Physiology of Cognitive Processes}, Krapp E, Papageorgiou E, Schiefer U, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Smirnakis SM{stelios}}
}

@Poster{ 7062,
title = {Predicting surface EEG power through fluctuations in intracortical signals during different behavioral and pharmacological conditions},
year = {2010},
month = {11},
volume = {40},
number = {343.15},
abstract = {Although non-invasive EEG is one of the most widely used tools for studying brain activity in humans, we still lack a clear understanding of how EEG signals are related to the spatio temporal organization of the underlying neuronal activity. In particular, it remains unknown how changes in cortical power and synchrony are reflected in the surface EEG signal. Here, we present an approach which incorporates the power and coherence of local field potentials (LFPs) in the striate cortex (V1) to predict fluctuations in the surface EEG signal. We made simultaneous recordings of neural activity with one surface EEG and multiple intracortical electrodes in two awake monkeys during different behavioral conditions as well as under the effect of local Lidocaine injections. Using a General Linear Model (GLM), we found that both LFP power and coherence conveyed individual information which could be used to accurately reconstruct trial-by-trial fluctuations in EEG power. Furthermore, predictive power of the GLM was very robust across different behavioral conditions but highly dependent on frequency. While EEG power could be modeled with high accuracy in the high frequency regime (R^2=0.719±0.042), predictive power vastly reduced for lower frequencies (R^2=0.0795±0.029). During application of Lidocaine, LFP power was reduced, however, inter-electrode coherence strongly increased, resulting in a scenario where the local cortical area was attenuated, though highly synchronized. Interestingly, the EEG showed an overall increase in power under these conditions, being strongest in higher frequencies, which emphasizes its ability to react to changes in synchrony even when the overall power of cortical activity is diminished. The results of our study emphasize two main points: First, our data demonstrates that EEG power indeed depends on changes in both cortical power and coherence and their combination can be used to explain EEG fluctuations across different brain states and stimulus conditions. However, this was mainly true for higher frequencies - perhaps due to larger spatial diversity of high frequency activity across cortical tissue, in which changes in cortical coherence convey more information about fluctuations in EEG power. Second, the local application of Lidocaine did not only reduce LFP power in the affected area but also introduced a strong increase in cortical coherence. Therefore, Lidocaine, which is currently mainly used as a local anesthetic, could be of great value in scientific studies which seek to selectively reduce cortical power while increasing cortical coherence in a localized area.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Musall S{unone}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Whittingstall KS{kevin}{Department Physiology of Cognitive Processes}}
}

@Poster{ 7073,
title = {The face selective activity in ventral temporal lobe in macaques},
year = {2010},
month = {11},
volume = {40},
number = {834.2},
abstract = {Face perception is one of the most crucial abilities for social animals like humans and nonhuman primates. fMRI-, lesion- and electrophysiology studies in humans and monkeys have indicated the existence of a dedicated and wide-spread face-processing network. In humans the most robust face-selective brain areas are fusiform face area (FFA), occipital face area (OFA) and superior temporal sulcus (STS). However, in monkeys the strongest face selectivity is found predominantly in STS, and no reliable face selectivity has been reported in fusiform gyrus and occipital temporal region. These differences may be a species difference, or they may be due to technical difficulties, because in monkeys the fusiform gyrus and ventral occipital-temporal area are located in regions that are difficult to map with fMRI due to susceptibility artifacts from the ear canal. Here we used an optimized imaging protocol at 7T, which does not suffer from the usual signal loss in inferior temporal areas. We investigated the functional organization of face processing in 5 awake or anesthetized macaques while the subjects viewed faces, fruit, houses and fractal patterns.
We found face-specific BOLD responses in STS, anterior medial temporal sulcus (AMTS), the regions anterior and lateral to AMTS and amygdala, consistent with previous fMRI and electrophysiology results. But in addition, entorhinal cortex (EC), ventral TE (posterior to AMTS), and hippocampus also contain face selective patches. These areas have not been reported to be face-selective in monkeys before, although they were shown to be responsive to faces with fMRI or intracortical recording in humans. The results indicate that there is much more extensive face selective brain activity than earlier studies have found in monkey ventral temporal lobe and suggests a large degree of similarity between the human and monkey face-processing network.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Ku S-P{shihpi}{Department Physiology of Cognitive Processes}, Tolias AS{atolias}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Goense J{jozien}{Department Physiology of Cognitive Processes}}
}

@Poster{ 7059,
title = {Vocal and non-vocal acoustic communication systems in the macaque brain},
year = {2010},
month = {11},
volume = {40},
number = {275.6},
abstract = {Humans and non-human primates such as macaques possess brain regions dedicated to segregating and processing vocal communication sounds from the environment and encoding their meaning. Brain regions that are strongly activated by conspecific vocalizations encompass the auditory cortices and higher-level regions in the temporal and frontal lobes. However, human imaging studies also implicate other brain regions in processing complex sounds and vocal and non-vocal communication signals such as speech or music. Hence our overall goal is to investigate the neural basis of how communication signals are processed across these regions.
One such area activated to speech is the insular cortex. Studying a vocal primate we identified a predominantly auditory region in the caudal insula where neurons, when probed with a range of natural sounds, responded preferentially to conspecific vocalizations. This preference also existed over acoustically manipulated versions of these vocalizations, demonstrating insula sensitivity to the spectral and temporal features of these sounds. These findings characterize the caudal insula as an auditory region preferentially responding to vocal communication sounds.
We also identified a sub-region within the claustrum, a structure located beneath the insula and reciprocally connected to the entire cortex, which responded to acoustic stimuli. Neurons here displayed increased firing rates at the onset of stimulus presentation and not integrate audio-visual information. They did however respond preferentially to vocalizations or events that were highly salient suggesting a role for the claustrum in saliency detection.
Human acoustic communication is not restricted to vocal sounds, but also includes non-vocal sounds or acoustic gestures. Here we report that macaque monkeys display drumming behaviors that not only attract the attention of listening monkeys as similarly as conspecific vocalizations but also influence their social interactions. Using high-resolution functional imaging we identified brain regions preferentially activated by drumming sounds or vocalizations, and found that they are both represented in higher-order regions within the auditory cortex and the amygdala. These results suggest a common origin of primate vocal and non-vocal communication systems and a likely common origin of human speech and music.
Overall, we show that vocal communication sounds are processed not only in the auditory cortices but also in the insula and claustrum. Furthermore, specialized networks that evolved to process vocalizations are also used to process non-vocal communication sounds in a similar manner.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Remedios R{ryan}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Poster{ FrankeMNHPLEMO2010,
title = {Online 3D simulation of extracellular recordings with morphologically reconstructed neurons},
journal = {Frontiers in Computational Neuroscience},
year = {2010},
month = {10},
volume = {2010},
number = {Conference Abstract: Bernstein Conference on Computational Neuroscience},
abstract = {Extracellular recordings are a key tool to study the activity of neurons in vivo. Especially in the case of experiments with behaving animals, however, the tedious procedure of electrode placement can take a considerable amount of expensive and restricted experimental time. Furthermore, due to tissue drifts and other sources of variability in the recording setup, the position of the electrodes with respect to the neurons under study can change, causing low recording quality. Here, we developed a system online simulation of extracellular recordings that allows for feedback from electrode positioning systems.
The simulator is based on realistically reconstructed 3D neurons. The shape of the extracellular waveform is estimated from their morphology for every point on a 3D grid around the neurons. If a recording device is close to a neuron, the corresponding waveform for its spikes is calculated from that grid by interpolating the waveforms of the adjacent grid positions. This way we can simulate a realistic recording environment in which an unconstrained movement of electrodes and neurons and an interaction with a positioning system and online spike sorter is possible.},
web_url = {http://www.frontiersin.org/10.3389/conf.fncom.2010.51.00128/event_abstract},
event_name = {Bernstein Conference on Computational Neuroscience (BCCN 2010)},
event_place = {Berlin, Germany},
state = {published},
DOI = {10.3389/conf.fncom.2010.51.00128},
author = {Franke F, Meier P, Natora M, Hagen E, Pettersen KH, Linden H, Einevoll GT, Munk MH{munk}{Department Physiology of Cognitive Processes} and Obermayer KH}
}

@Poster{ 7066,
title = {Oscillatory neuronal synchronization between prefrontal and extrastriate visual cortex during visual memory},
year = {2010},
month = {10},
volume = {40},
number = {485.2},
abstract = {Visual memory involves the timely interaction of distributed neural ensembles across the brain. However, how distant neural sites cooperate during visual memory is still an open question. In this study we investigate the neural interaction between two cortical areas, the extra striate visual area V4 and the lateral prefrontal cortex based on simultaneous recordings of local field potentials (LFP) and single unit activity (SUA) in V4 and PF while two rhesus monkeys performed a delayed matching to sample task. Specifically, we analyzed LFPs from 131 sites recorded in V4 (86/45 for monkeys 1/2) and 117 sites in PF (74/43 for monkeys 1/2) from 20 and 11 recording sessions in 2 monkeys.
This results in a total amount of 507 pairs of simultaneously recorded channels. When we analyzed the phase locking (PL) of the LFP, we observed enhanced PL during the memory period of the task between both areas that predominantly occurred in the theta frequency range (3-8Hz). Here, 135/332 and 33/175 pairs for monkey 1 and 2 showed significantly elevated phase locking during the delay period of the task (Z-Test for significant proportion p<0.001). To test whether the increase in theta phase locking at the mesoscopic level of LFPs was accompanied by an increased phase locking between spiking activity and theta oscillations across both areas, we examined whether spiking systematically varied as a function of theta phase. We found that spike-phase locking significantly increased during delay compared to baseline for both V4 units locked to prefrontal theta (Z=6.5/5.7, p<0.01, M1/2, N=458/202 unit-channel pairs) and vice versa (Z=5.5/3.7, p<0.02 M1/2, N=335/258 pairs). Taken together, our results suggest that theta based oscillatory synchrony between V4 and PF cortex most likely provides a basis for the timely coordination of spiking output of V4 and prefrontal neurons during visual short- term memory. These findings may reflect enhanced inter-regional communication of visual information during the retention period and support the important role of oscillatory synchronization in controlling neural interactions across large-scale networks during visual cognition.},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Liebe S{sliebe}{Department Physiology of Cognitive Processes}, Hoerzer G, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ MishraPL2010,
title = {PyroEGTA-Derived Metal Ion Responsive Probes for MRI},
year = {2010},
month = {9},
volume = {2010},
number = {0909B},
abstract = {For proper brain development and function, a critical relationship exists between the elements calcium, magnesium and zinc. Their deficiency or excess accumulation in the body may cause several diseases. Thus, in vivo determination of the distribution of these metal ions is extremely desirable. Recently, advances have been made in the design of responsive probes sensitive to certain metal ions.1,2 The use of MRI to detect fluctuations in the concentration of vital metal ions has recently received much attention. However, there is still a need to develop more sensitive and selective probes for biologically important metal ions. Here, we describe two structurally different pyro-EGTA derived lanthanide complexing DO3A probes, which respond to changes in Ca2+ and Zn2+ concentrations at physiological pH. The complex [LnL1] contains a LnDO3A moiety coupled to a carbomethoxy group of the pyroEGTA derivative [2,2'-(2-(2-(carboxymethoxy)phenoxy)ethylazanediyl)diacetic acid] via an amide bond. This complex possesses six coordination sites suitable for sensing small ionic radii (Zn2+, Mg2+) metal ions. The complex [LnL2] contains eight coordination sites, appropriate for larger ions such as Ca2+. Changes in relaxivity were monitored following addition of appropriate divalent metal ions. In vitro relaxivity measurements were performed at physiological pH in competitive aqueous media at 1.4T and 37oC. [GdL1] showed a 66% relaxivity change on addition of Zn2+. This molecule responded selectively to Zn2+ rather than Ca2+ and Mg2+. [GdL2] showed a relaxivity change of 64% upon addition of Ca2+ and was insensitive to other added divalent ions in the millimolar range. Parallel luminescence titrations were also undertaken with [EuL1] and [EuL2] in the presence and absence of various divalent ions. Changes in europium emission spectra and the modulation of q values were observed upon addition of Zn2+ and Ca2+ for [EuL1] and [EuL2], respectively. Thus, enhancements in hydration numbers were found were, in accord with the variations in relaxivity. 1. Que E. L. et al, Chem Soc Rev. 2010;39 (1):51-60. 2. Reany O. et al, J. Chem. Soc. Perkin. Trans. 2, 2000, 1819-1831.},
web_url = {http://www.wmicmeeting.org/2010/Abstracts/forSystemUse/papers/P0909B.html},
event_name = {2010 World Molecular Imaging Congress (WMIC)},
event_place = {Kyoto, Japan},
state = {published},
author = {Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Parker D and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ AngelovskiMEGBPL2010,
title = {The Use of Gadolinium-based Contrast Agents for Molecular and Cellular MRI: Quantitative Considerations},
year = {2010},
month = {9},
volume = {2010},
number = {0945B},
abstract = {Magnetic resonance imaging (MRI) is a powerful tool in clinical diagnostics and is also used for the understanding of developmental and biological processes. It visualizes the differences in tissues and organs, as well as between normal and pathological states. Due to its noninvasive nature, excellent spatial resolution and tissue penetration, MRI became one of the preferential methods for molecular and cellular imaging. The specificity and sensitivity of MRI can be further enhanced by the introduction of contrast agents. Many of the currently existing contrast agents are restricted to the extracellular space, though novel approaches enforce generations of intracellular contrast agents that can be developed for targeted labeling of cells for the visualization of a specific biological process. However, the lower sensitivity of MRI as compared to other imaging techniques demands certain quantitative considerations for the rational design of these intracellular agents. Gadolinium complexes are the most frequent choice for T1-weigthed MR-imaging. Besides having a high longitudinal relaxivity (r1), these agents should also be delivered in a sufficient amount to target structures on the cell membrane or inside the cells. We have performed a study in an attempt to determine the minimum number of gadolinium ions needed for the efficient labeling of cells. The concentration dependent contrast enhancement of Gd-DOTA, Gd-DO3A or Gd-AAZTA in T1-weighted MR-images of phantoms with water only, cell culture medium containing serum, or in the presence of cells was followed at different, ultra-high magnetic fields (3T, 7T, 16.4T) and with the spatial resolution commonly used for in vivo measurements. The results suggest MRI detectability at low micromolar concentrations for all applied contrast agents, which correspond to the previously predicted number of metal atoms per cell [1]. However, this number is dependent on the r1 of the contrast agent and the magnetic field of the imaging scanner. Financial support of the Max-Planck Society and German Ministry for Education and Research (BMBF, FKZ: 01EZ0813) is gratefully acknowledged.},
web_url = {http://www.wmicmeeting.org/2010/Abstracts/forSystemUse/papers/P0945B.html},
event_name = {2010 World Molecular Imaging Congress (WMIC)},
event_place = {Kyoto, Japan},
state = {published},
author = {Angelovski G{goran}{Department Physiology of Cognitive Processes}, Mamdeov I{ilgar}{Department Physiology of Cognitive Processes}, Engelmann J{joern}{Department High-Field Magnetic Resonance}, Gottschalk S{sgott}{Department High-Field Magnetic Resonance}, Balla DZ{ballad}{Department High-Field Magnetic Resonance}, Pohmann R{rolf}{Department High-Field Magnetic Resonance} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ MamedovPLA2010,
title = {Title Dinuclear Heterometallic Lanthanide Complexes Exhibiting MRI and Luminescence Response},
year = {2010},
month = {9},
volume = {2010},
number = {0902A},
abstract = {Heteronuclear lanthanide complexes have gained an increased level of interest recently, due to their high potential for application in various molecular imaging techniques. They appear primarily as the most rational choice for agents to be used in multimodal imaging approaches.[1-2] Namely, due to their versatile physicochemical properties, they are widely used in MRI or luminescence imaging. Several lanthanide complexes have been reported recently with the potential to be used as multimodal agents. Depending on the approach the final ligand structure contained a single chelator for the lanthanide ion, or consisted of two chelating units, consequently bearing same or different Ln3+. Following these principles, we designed and synthesized a ligand containing two different chelators where the antenna acts not only as a linker between these two chelators, but also as an integral component in one of their structures. The macrocyclic, DOTA-type moiety of this ligand forms a stable complex with Eu3+ and Gd3+ which exhibit the expected luminescence emission and relaxometric characteristics, respectively. An aryl-containing acyclic chelator 5A-PADDTA (abbreviated from 5-aminoisophthalamide diethylenediaminetetraacid) of this ligand also forms complexes with lanthanides and their existence is confirmed by the means of luminescence and NMR spectroscopy. Depending on the choice of the metal ion (Gd3+, Tb3+, Eu3+, Nd3+, Yb3+ or Er3+), the system could act as a potential dual-modal (MRI / Vis or NIR luminescence imaging) or dual-emissive (luminescence imaging at various wavelengths in Vis/NIR region) contrast agent.},
web_url = {http://www.wmicmeeting.org/2010/Abstracts/forSystemUse/papers/P0902A.html},
event_name = {2010 World Molecular Imaging Congress (WMIC)},
event_place = {Kyoto, Japan},
state = {published},
author = {Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, Parac-Vogt T, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Angelovski G{goran}{Department Physiology of Cognitive Processes}}
}

@Poster{ FischerBLB2010,
title = {Functional characteristics of a motion responsive region in the posterior cingulate cortex compared to V5/MT and MST},
journal = {Perception},
year = {2010},
month = {8},
volume = {39},
number = {ECVP Abstract Supplement},
pages = {95},
abstract = {Motion processing regions apart from V5+/MT+ are still relatively poorly understood. The cingulate sulcus visual area (CSv) in the dorsal posterior cingulate cortex (dPCC) was previously described to respond preferentially to coherent motion and implied in ego-motion processing. We used fMRI to compare responses of CSv/dPCC and of areas V5/MT and MST to distinct types of motion and self-motion cues such as retinal motion and objective motion, determined during pursuit. Both V5/MT and MST had a strong preference for contra- versus ipsi-lateral stimulation, no preference for 2D planar motion versus 3D flow, and reduced yet significant responses to random motion. In contrast, CSv/dPCC preferred 2D planar motion over 3D flow, showed no lateralization, and did not respond to random motion. All areas responded strongly to eye-movement related signals, however CSv responded more to ‘real’ motion than to retinal motion while the reverse was the case for V5/MT and MST. CSv/dPCC thus differs from other motion-responsive regions by its unique preference to full-field, coherent and planar motion cues and its enhanced capability to respond to real motion. These results place CSv/dPCC in a good position to process visual and non-visual cues related to self-induced motion, especially those associated to eye-movements.},
web_url = {http://www.perceptionweb.com/abstract.cgi?id=v100307},
event_name = {33rd European Conference on Visual Perception},
event_place = {Lausanne, Switzerland},
state = {published},
author = {Fischer E{efischer}{Department Physiology of Cognitive Processes}, B\"ulthoff HH{hhb}{Department Human Perception, Cognition and Action}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ NevesEEBL2010,
title = {Mapping noradrenergic projections from locus coeruleus using classical fluorescent tracer and MRI-visible contrast agent},
year = {2010},
month = {7},
volume = {7},
number = {087.13},
abstract = {We examined anterograde labeling of noradrenergic terminals originating from the neurons of brain stem neuromodulatory nucleus Locus Coeruleus (LC), a major course of noradrenaline in the rat forebrain, by means of simultaneous iontophoretic injection of paramagnetic (Mn2+) and classical (fluorescent dextran) tracers in the LC. In order to detect Mn2+ transport, MRI scanning was performed in each rat before and 24h after injection and, subsequently, MR images were compared using voxel-based t-test (voxel size: 0.25x0.25x0.25mm). Fluorescent dextran monosynaptic anterograde transport was analysed 5 days after injection. Iontophoretic injection of Mn2+ did not produce neurotoxic effects as there were no signs of neuronal death or glial inflammatory reaction at the injection site 5 days after injection. Both methods revealed reliable labeling in major subcortical terminal fields of LC neurons (Swanson and Hartman, 1975; Ungerstedt, 1971) including central nucleus of amygdala, internal capsule, anterior part of bed nucleus of the stria terminalis, and mesencephalic region. Consistent with previous studies, labeling was predominantly ipsilateral to the injection site. Classical tracer readily detected terminals like fibers of passage typical for noradrenergic innervation of cortical regions. In contrast, manganese-enhanced MRI (MEMRI) method failed to visualize such dispersed noradrenergic innervation in the cortex. On the other hand, MEMRI might be more sensitive for detecting patterns of functional connectivity. Consistent and strong Mn-labeling in hippocampus was observed, which was not proportional to anatomical connectivity labeled by dextran. Thus, the tract-tracing using MEMRI preferentially maps the target sites of rather strong and highly concentrated projections, but not dispersed terminal fields. Despite the relatively low resolution of MEMRI technique compared to florescent microscopy, this novel tract-tracing method can be successfully applied for visualization of major neural pathways and their reorganization in the same animal in longitudinal studies including those concentrating on development, aging, plasticity, or disease-related neurodegeneration.},
web_url = {http://fens2010.neurosciences.asso.fr/},
event_name = {7th Forum of European Neuroscience (FENS 2010)},
event_place = {Amsterdam, Netherlands},
state = {published},
author = {Neves RM{ricardo}{Department Physiology of Cognitive Processes}, Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}, Evrard H{evrard}{Department Physiology of Cognitive Processes}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ MagriEPS2010,
title = {Noradrenergic neurons of the locus coeruleus are phase-locked to cortical updown states during sleep},
year = {2010},
month = {7},
volume = {26},
pages = {95},
abstract = {The activity of all major ascending neuromodulatory arousal systems is greatly reduced
during the periods of cortical synchronization that are reflected in EEG as
high-amplitude low-frequency waves. Despite the relative silence, neuromodulatory
neurons typically switch their firing pattern from a tonic mode during the alert,
desynchronized cortical state to a bursting mode during cortical synchronization
that is characteristic for slow wave sleep (SWS) or anesthesia. The bursting activity
is particularly efficient for a corresponding release of neuromodulators in the target
regions. The activity of brainstem cholinergic and dopaminergic neurons correlates
with cortical slow oscillations, while activity of the noradrenergic system in this context
remains unexplored. We recorded unit activity of the noradrenergic neurons of the
locus coeruleus (LC) with simultaneous monitoring of the cortical state by EEG in
behaving rats. Here we report that the activity of LC neurons is phase-locked to cortical
slow oscillations indicative of up-down states. In addition, we show that LC neurons
lock best to slow oscillations advanced by approximately 100 ms, suggesting a possible
noradrenergic contribution to generation of cortical up state. These results provide the
first strong evidence for a cortico-coerulear interaction during SWS and challenge a
conventional dogma about a quiescent state of the LC-noradrenergic system during
sleep. The phase-locking of noradrenergic neurons to cortical slow oscillations may
have a strong impact on the coordinated activity of neuronal assemblies during up
states, which might be relevant for off-line information processing, synaptic plasticity
and memory consolidation.},
file_url = {fileadmin/user_upload/files/publications/Sum10Program-Magri.pdf},
web_url = {http://www1.nin.knaw.nl/summerschool/},
event_name = {26th International Summer School of Brain Research: Slow Brain Oscillations of Sleep, Resting State and Vigilance},
event_place = {Amsterdam, Netherlands},
state = {published},
author = {Magri C{cmagri}{Department Physiology of Cognitive Processes}, Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}, Panzeri S{stefano} and Sara SJ}
}

@Poster{ PietrajtisSLE2010,
title = {Spike timing among neurons recorded simultaneously in locus coeruleus, ventral tegmental area and frontal cortex during somatosensory stimulation: LC leads!},
year = {2010},
month = {7},
volume = {7},
number = {087.17},
abstract = {The locus coeruleus (LC) and ventral tegmental area (VTA) are the source of noradrenergic and dopaminergic innervation of the medial prefrontal cortex (mPFC). These ascending projections to mPFC have been implicated in a broad range of cognitive processes in rodents and primates, but their relative contribution to mPFC function remains elusive. Determining temporal relations in spontaneous and evoked firing in the three regions is a necessary step toward understanding how the two neuromodulators might work in concert to regulate cognition.
To this end, unit activity and local field potentials were recorded simultaneously from VTA, LC and mPFC. A number of electrophysiological and pharmacological criteria were used to identify VTA and LC neurons. After a period of recording of spontaneous activity, evoked responses were elicited by electrical shock to the hind paw. Shocks were single pulses (0.5ms, 5mA) or trains of 5 pulses, delivered at 50Hz.
LC neurons responded to the single paw shock with a short latency ~ 20 ms, phasic burst, followed by brief inhibition. Trains elicited stronger responses, often biphasic, followed by prolonged inhibition. Most of the electrodes in the mPFC were located in the anterior cingulate area, where there was no response to single pulses. Trains elicited tonic excitatory responses with latencies of more than 100 ms, usually followed by inhibition, sometimes even entraining several cycles of slow oscillation. VTA neurons did not respond to the single pulse. Trains elicited excitatory responses in a small number of VTA cells, with latencies always greater than 100 ms. Both spontaneous and evoked activity of these VTA neurons was highly synchronised with mPFC activity; cortical activity always led VTA by several milliseconds.
The results confirm that the LC neurons have a very low threshold and respond with a short latency to somatosensory stimulation. Corresponding release of noradrenaline will modulate sensory responses in the target regions including mPFC and VTA. The long response latency of the VTA cells suggests that its ascending projection does not play an important role in modulating mPFC response, but rather is driven by cortex and possibly modulated by LC.},
web_url = {http://fens2010.neurosciences.asso.fr/},
event_name = {7th Forum of European Neuroscience (FENS 2010)},
event_place = {Amsterdam, Netherlands},
state = {published},
author = {Pietrajtis K{kpietrajtis}{Department Physiology of Cognitive Processes}, Sara SJ, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}}
}

@Poster{ FrankeMNHPLEMO2010_2,
title = {A simulated extracellular recording environment for the evaluation of automated electrode positioning systems and spike sorting algorithms},
year = {2010},
month = {6},
abstract = {Extracellular recordings are a key tool to study the activity of neurons in vivo. Especially in the case of experiments with behaving animals, however, the tedious procedure of electrode placement can take a considerable amount of expensive and restricted experimental time. Furthermore, due to tissue drifts and other sources of variability in the recording setup, the position of the electrodes with respect to the neurons under study can change, causing low recording quality. Here, we developed a system online simulation of extracellular recordings that allows for feedback from electrode positioning systems.
The simulator is based on realistically reconstructed 3D neurons. The shape of the extracellular waveform is estimated from their morphology for every point on a 3D grid around the neurons. If a recording device is close to a neuron, the corresponding waveform for its spikes is calculated from that grid by interpolating the waveforms of the adjacent grid positions. This way we can simulate a realistic recording environment in which an unconstrained movement of electrodes and neurons and an interaction with a positioning system and online spike sorter is possible.
ACKNOWLEDGMENTS
This work was supported by DFG GRK 1589/1 and the German Federal Ministry of Education and Research (BMBF) with the grants 01GQ0743 and 01GQ0410 and by the Research Council of Norway (eScience,NeuroNor).},
web_url = {http://www.g-node.org/events/symposium2010},
event_name = {G-Node Inaugural Symposium},
event_place = {Martinsried, Germany},
state = {published},
author = {Franke F{ffranke}{Department Physiology of Cognitive Processes}, Meier P, Natora M, Hagen E, Petersen KH, Linden H, Einevoll GT, Munk MH{munk}{Department Physiology of Cognitive Processes} and Obermayer K}
}

@Poster{ ZaretskayaTLB2010,
title = {Binocular Rivalry: a Causal role of the Parietal Cortex in Perceptual Selection},
year = {2010},
month = {6},
volume = {16},
number = {145 MT-AM},
pages = {8},
web_url = {http://www.humanbrainmapping.org/files/2010MeetingFiles/OHBM%202010%20Abstract%20Book.pdf},
event_name = {16th Annual Meeting of the Organisation for Human Brain Mapping (HBM 2010)},
event_place = {Barcelona, Spain},
state = {published},
author = {Zaretskaya N{nataliya}{Department Physiology of Cognitive Processes}{Department High-Field Magnetic Resonance}, Thielscher A{thielscher}{Department High-Field Magnetic Resonance}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6818,
title = {Categorical Representation of a Human/Monkey Face Continum in the Human and Non-Human Primate Temporal Lobe},
year = {2010},
month = {6},
volume = {2010},
pages = {93},
abstract = {Categorization of faces is fundamental for social interactions of primates. To understand its neural basis, we investigate how human and monkey face categories are represented in both the human and non-human primate brain. As stimuli, we use realistic three-dimensional morphed faces that linearly span the continuum between humans and monkeys (Fig. 1A).
Extensive behavioral tests in both species revealed categorical perception with a shift of the categorical boundary towards the own species (Fig. 1B). This suggests that both species perceive the same stimulus continuum in a fundamentally different way. During a fixation task, we recorded from the temporal lobe extracellular signals in monkeys and BOLD signals in humans. To analyze the data, we used a multivariate pattern classifier approach based on
Support Vector Machines and correlations. Consistent with the psychophysical results, we found an "own-species" bias in the categorical representation of human and monkey faces
at the level of single neurons as well as in the population response in the inferior temporal lobe of the monkey. (Fig. 1C). Symmetrically, we found a categorical response with an ownspecies bias in the activation patterns of the left human STS. In addition, human ventral temporal cortex showed a higher sensitivity for human faces. Our results are the first to demonstrate the neural basis of categorical representation of a facial attribute in the
primate brain. In addition, our data show that both psychophysical and neuronal data can show categorical boundary shifts indicative of the behavioral relevance of prototypical categories.},
web_url = {http://www.areadne.org/2010/home.html},
editor = {Hatsopoulos, N. G., S. Pezaris},
event_name = {AREADNE 2010: Research in Encoding And Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Sigala R{sigala}{Department Physiology of Cognitive Processes}, Schultz J{johannes}{Department Human Perception, Cognition and Action}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ 6812,
title = {Cholinergic Dependence of a Cognitive Task},
year = {2010},
month = {6},
volume = {2010},
pages = {46},
abstract = {Acetylcholine (ACh) is a neurotransmitter implicated in several cognitive functions and is believed
to especially affect the acquisition of new information. Learning adapts behavior to
new situations and to new categories of stimuli.
We have examined the effects of scopolamine, an antagonist of muscarinic ACh receptors,
on object categorization. Extensive behavioral pharmacological studies were carried out in
two macaques. Performance was disrupted following injections of scopolamine. When the
stimuli presented were novel, ie. when they had not been seen before the experiment,
scopolamine significantly impaired performance in the categorization task. The monkeys
were less impaired in categorizing a set of familiar stimuli, ie. stimuli that they had categorized
successfully in previous sessions. Performance also deteriorated as the stimulus became
less salient by an increase in the level of visual noise.
One of the questions of the role of cholinergic neurons in networks involved in the learning
of new stimuli and in the performance of the categorization task is the type of information
that they convey. Our recordings are aimed towards making the study of information in
these networks feasible through simultaneous recordings of several neurons during the performance
of a complex behavioral task requiring responses to a series of discrete stimuli at
parametrically varied salience levels, belonging to two categories and two familiarity levels.
In addition to the behavioral experiments, neuronal activity was recorded in one monkey
during a fixation task in which the monkey was presented with stimuli belonging to two categories.
Preliminary recordings of neuronal ensembles have been made using tetrodes or
polytrodes in the putamen, globus pallidus and nucleus basalis. All these regions have
cholinergic neurons. Whereas cholinergic neurons in the basal ganglia are interneurons involved
in local networks, their role is likely to be important as the basal ganglia are a crucial
component in a circuit that underpins learning of conditional tasks. The nucleus basalis and
other regions of the basal forebrain, on the other hand, have cholinergic neurons that
project to the amygdala, hippocampus and cerebral cortex and are considered essential
components in a variety of cognitive behaviors, including the formation of new memories.
Neurons in the putamen had no visual responses but they anticipated the reward at the end
of each trial. Neurons in the globus pallidus and the nucleus basalis were also reward predicting
but could have in addition visual responses. These responses are related to the task
performed by the monkey and may be important in the performance of the categorization
task, in which case the prediction would be that the responses would be affected when categorization
is impaired by scopolamine.},
file_url = {fileadmin/user_upload/files/publications/AREADNE-2010-Aggelopoulos.pdf},
web_url = {http://www.areadne.org/2010/home.html},
editor = {Hatsopoulos, N. G., S. Pezaris},
event_name = {AREADNE 2010: Research in Encoding And Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Aggelopoulos NC{aggelopoulos}{Department Physiology of Cognitive Processes}, Melano T{tmelano}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ 6810,
title = {Decorrelated Firing in Cortical Microcircuits},
year = {2010},
month = {6},
volume = {2010},
pages = {58},
abstract = {Correlated trial-to-trial variability in the activity of cortical neurons is thought to reflect the
functional connectivity of the circuit. Many cortical areas are organized into functional columns,
in which neurons are believed to be densely connected and share common input. Numerous
studies report a high degree of correlated variability between nearby cells. We developed
chronically implanted multi-tetrode arrays offering unprecedented recording quality
to re-examine this question in primary visual cortex of awake macaques. We found that
even nearby neurons with similar orientation tuning show virtually no correlated variability.
In a total of 46 recording sessions from two monkeys, we presented either static or drifting
sine-wave gratings at eight different orientations. We recorded from 407 well isolated, visually
responsive and orientation-tuned neurons, resulting in 1907 simultaneously recorded
pairs of neurons. In 406 of these pairs both neurons were recorded by the same tetrode.
Despite being physically close to each other and having highly overlapping receptive fields,
neurons recorded from the same tetrode had exceedingly low spike count correlations (rsc =
0.005 ± 0.004; mean ± SEM). Even cells with similar preferred orientations (rsignal > 0.5) had
very weak correlations (rsc = 0.028 ± 0.010). This was also true if pairs were strongly driven
by gratings with orientations close to the cells’ preferred orientations.
Correlations between neurons recorded by different tetrodes showed a similar pattern. They
were low on average (rsc = 0.010 ± 0.002) with a weak relation between tuning similarity
and spike count correlations (two-sample t test, rsignal < 0.5 versus rsignal > 0.5: P = 0.003, n =
1907).
To investigate whether low correlations also occur under more naturalistic stimulus conditions,
we presented natural images to one of the monkeys. The average rsc was close to zero
(rsc = 0.001 ± 0.005, n = 329) with no relation between receptive field overlap and spike
count correlations. We obtained a similar result during stimulation with moving bars in a
third monkey (rsc = 0.014 ± 0.011, n = 56).
Our findings suggest a refinement of current models of cortical microcircuit architecture and
function: either adjacent neurons share only a few percent of their inputs or, alternatively,
their activity is actively decorrelated.},
web_url = {http://www.areadne.org/2010/home.html},
editor = {Hatsopoulos, N. G., S. Pezaris},
event_name = {AREADNE 2010: Research in Encoding And Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Ecker AS{aecker}{Research Group Computational Vision and Neuroscience}, Berens P{berens}{Research Group Computational Vision and Neuroscience}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Bethge M{mbethge}{Research Group Computational Vision and Neuroscience}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Tolias AS{atolias}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6814,
title = {Noradrenergic Modulation of Spontaneous Activity and Sensoryevoked Responses in Prefrontal Cortex},
year = {2010},
month = {6},
volume = {2010},
pages = {60},
abstract = {Neural coding in medial prefrontal cortex (mPFC) is thought to underlie various cognitive behaviors
such as rule-guided learning, strategy use, or cognitive flexibility. Specifically, prefrontal
neurons display many behaviorally relevant correlates related to sensory perception,
motor responses, or reward that are believed to contribute to behavioral outcome. The
mPFC is the cortical region that receives exceptionally dense dopaminergic (DA) innervation
arising from the mesopontine Ventral Tegmental Area (VTA). Noradrenergic fibers originating
from the brain stem nucleus Locus Coeruleus (LC) are also dense in mPFC. Previous investigations
indicated that NA and DA systems have common target neurons in mPFC. The
ascending NA and DA projections to mPFC have been implicated in a broad range of cognitive
processes in rodents and primates including modulation of perception, attention, motivation,
or memory. It is still, however, unknown whether and how NA and DA affect the prefrontal
neural codes.
To address this question, we performed simultaneous recordings of unit activity and local
field potentials in mPFC, VTA and LC in the rat. We first studied temporal relations of firing
activity in the three brain regions during spontaneous and evoked activity under anesthesia.
Mild electric shocks were applied to the rat hind paw for somatosensory stimulation. The LC
neurons responded to a single foot shock (1ms, 5mA) with a short latency (~20ms), phasic
burst, followed by brief inhibition. Trains of pulses (100ms, 50Hz, 5mA) elicited much
stronger responses. The mPFC and VTA neurons did not respond to a single foot shock.
Trains elicited sustained (~1s) excitatory responses in a subpopulation of mPFC neurons
with latencies of ~100ms, usually followed by inhibition. Trains elicited both excitatory and
inhibitory responses in a small number of putative dopaminergic, VTA cells, with latencies
always greater than 100ms. Both spontaneous and evoked activity of VTA neurons was highly
synchronized with mPFC activity; cortical activity always led VTA by several milliseconds.
In some cases, sensory stimulation resulted in entrainment of mPFC and VTA neurons in several
cycles of slow oscillation. Next, we inhibited the LC by systemic or local application of
clonidine, an α2-adrenergic receptor agonist. This manipulation dramatically abolished the
excitatory evoked responses in both VTA and mPFC without having much effect on spontaneous
activity.
The results indicate that short-latency responses of LC neurons to somatosensory stimulation
with corresponding release of NA modulate sensory responses in the target regions including
mPFC and VTA. The long-latency responses of the VTA cells suggest that its ascending
projections do not play an important role in modulating mPFC responses to noxious stimuli.
VTA activity is rather driven by mPFC and, possibly, modulated by LC.
We will further investigate NA modulation of mPFC codes in the rat performing a prefrontaldependent
task. To induce release of NA in mPFC, we will apply electrical microstimulation
to the LC just before presentation of discrimination stimuli, mimicking the burst activity of
LC typically observed in response to salient stimuli. We expect to see more robust coding in
the mPFC correlated with better behavioral performance in the presence of LC activation.},
web_url = {http://www.areadne.org/2010/home.html},
editor = {Hatsopoulos, N. G., S. Pezaris},
event_name = {AREADNE 2010: Research in Encoding And Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}, Pietrajtis K{kpietrajtis}{Department Physiology of Cognitive Processes}, Sara SJ and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6816,
title = {Primary Visual Cortex Encodes Complementary Information about
Naturalistic Movies at Different Temporal Scales},
year = {2010},
month = {6},
volume = {2010},
pages = {77},
abstract = {Natural stimuli modulate the activity of visual cortex on a variety of temporal scales, yet it is
still unclear whether visual cortical neurons employ more than one response time scale to
encode such stimuli. We investigated this issue by analyzing the activity of neurons recorded
in primary visual cortex (V1) of anesthetized macaques during binocular presentation of
naturalistic color movies, and we used information theory to quantify the amount of information
carried by neural codes operating at different temporal scales.
We divided the recording time into stimulus windows of 40–80 ms, and we computed the information
carried by the neural response in each window about which stimulus window was
being shown. First we measured the information carried by the spike count, simply quantified
by the total number of spikes in the stimulus window. Then we measured the information
carried by the temporal pattern of spikes, the latter being computed by subdividing
each stimulus window into smaller time bins of size Δt and converting the spike train into a
sequence of 0s and 1s denoting the absence/presence of spikes inside each bin [1]. When
considering temporal patterns of spikes with a temporal resolution Δt of 8 or 16 ms, the information
about which part of the movie was being shown conveyed by temporal spike patterns
was up to 15% more than that conveyed by the spike count. This information gain did
not increase further when considering resolutions finer than 8 ms, indicating that spike patterns
carry information with a resolution of 8–16 ms or coarser. A previous study [2] showed
that V1 neurons encode information also with respect to the phase of low frequency (1–4 Hz
range) Local Field Potential (LFP) fluctuations. We investigated whether spike patterns carried
information complementary to that carried by the phase of firing by quantifying if the
joint knowledge of the precise spike pattern and the LFP phase of firing carried more information
than either code considered alone. We found that this was the case: The information
about the scene of the movie being shown gained by the simultaneous knowledge of the
phase of low frequency LFPs and of the spike patterns occurred [3] was 50% higher than the
information carried by spike patterns alone and 15 % higher than the information carried by
the phase of firing alone. This suggests that the information carried by slow LFP fluctuations
complements that carried by spike patterns.
In summary, we found evidence for multiple and complementary response time scales for
the encoding of naturalistic stimuli in visual cortex. Informative codes range from spike timing
precision at 10ms resolution to the much coarser phase of firing with respect to low frequency
(few Hz) fluctuations. These findings suggest that, as hypothesized e.g. in [3,4], sensory
cortices may enhance their information capacity by multiplexing complementary information
at different time scales.},
web_url = {http://www.areadne.org/2010/home.html},
editor = {Hatsopoulos, N. G., S. Pezaris},
event_name = {AREADNE 2010: Research in Encoding And Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Mazzoni A, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Martinez J, Quiroga RQ, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Poster{ 6817,
title = {Reduction of Correlated Noise in the Macaque Prefrontal Cortex during Conscious Visual Perception},
year = {2010},
month = {6},
volume = {2010},
pages = {82},
abstract = {The cortical mechanisms mediating visual awareness are thought to exploit a large
population of similarly tuned neurons explicitly representing a perceptually dominant visual
pattern through changes in its mean firing rate. However, inherent limitations of population
rate coding schemes such as noise detected in the correlated response variability across
neurons could constrict the encoding power of such a cortical network and thus decrease
the probability of this encoding strategy. Studying the differences in the noise correlation
structure of a tuned population between purely sensory visual stimulation subjective visual
perception could thus provide fundamental insights into the mechanisms of conscious visual
perception. Here we show that in the macaque prefrontal cortex perceptual dominance
under conditions of visual rivalry is accompanied by decorrelated discharges across neurons
sensory tuned to the dominant stimulus, compared to their significantly correlated
fluctuations when the same stimulus is perceived without competition. We propose that
noise decorrelation in prefrontal cortical circuits is optimal for achieving perceptual
dominance during visual awareness by substantially improving the encoding accuracy of the
dominant neuronal ensemble. Our findings also provide the first electrophysiological
demonstration of the contribution of prefrontal cortex to visual consciousness, a hypothesis
previously suggested by theoretical models as well as human functional imaging studies.},
web_url = {http://www.areadne.org/2010/home.html},
editor = {Hatsopoulos, N. G., S. Pezaris},
event_name = {AREADNE 2010: Research in Encoding And Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6813,
title = {Spatio-Temporal Coupling between Neural Activity and Bold Response in Primary Visual Cortex},
year = {2010},
month = {6},
volume = {2010},
pages = {51},
abstract = {Neural activity in the brain is correlated with the blood-oxygen level dependent (BOLD) contrast
which can be measured non-invasively by functional magnetic resonance imaging (fMRI).
Up to date, many fMRI analysis methods are based on simplifying assumptions about the BOLD
signal. Two popular assumptions are spatial independence and homogeneity of the haemodynamic
response function (HRF) across voxels. As single voxels usually are not independent
and moreover also exhibit different haemodynamic response characteristics, these assumptions
might lead astray interpretations of fMRI data.
In this study we present an analysis framework that reveals the spatio-temporal correlation
structure between simultaneously measured intracortical neurophysiological activity in primary
visual cortex of the non-human primate and BOLD response. Given the spectrograms of
neurophysiological activity and the simultaneously recorded BOLD data we compute a spatiotemporal
convolution that links the activity measured at the electrode to the multivariate
BOLD response. The convolution can be interpreted as the pattern in time-voxel space that
reflects best the neural activity as it maximises the canonical correlation [1] between neural
and haemodynamic activity.
Inspection of the estimated time-voxel patterns yields new insights in the spatio-temporal dependency
structure of neurovascular coupling mechanisms. This study thereby extends previous
results reported in [2,3], where the convolution was a time-frequency convolution estimated
for the neurophysiological activity.
We show results from data collected during spontaneous activity and during visual stimulation.
The analysis resulted in robust spatio-temporal coupling patterns across different experimental
conditions. We compared the multivariate patterns with univariate coupling measures and
spatial principal component analysis (SPCA), a popular method for connectivity analysis on
fMRI data. Our findings suggest that neither univariate methods nor unimodal methods such
as SPCA, which are based on autocorrelations of fMRI data only, can recover the multivariate
spatio-temporal coupling structure in primary visual cortex.},
web_url = {http://www.areadne.org/2010/home.html},
editor = {Hatsopoulos, N. G., S. Pezaris},
event_name = {AREADNE 2010: Research in Encoding And Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Biessmann F{fbiessma}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Meinecke FC, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and M\"uller K-R{klaus}}
}

@Poster{ 6815,
title = {The Time Scales of Information Representation in Auditory Cortex are Stimulus Dependent},
year = {2010},
month = {6},
volume = {2010},
pages = {66},
abstract = {Recent work has shown that in auditory cortex acoustic stimuli are potentially encoded by
different neural codes, each operating on different temporal scales. For example, the millisecond-
precise timing of individual neuron’s action potentials has been implicated similarly
as firing rate modulations on slower scales or the timing of spikes to ongoing oscillatory
background activity [1]. Here we asked whether the temporal precision of these putative
neural codes is fixed and inherent to the system, or whether their temporal precision is determined
by the acoustic stimulus.
Stimulus information in different codes was compared during stimulation with naturalistic
sounds and sequences of random tones. The natural sounds had a typical autocorrelation of
around 20–30 ms (computed from the envelope of individual frequency bands), while random
tones had a much shorter autocorrelation time (around 10 ms). Neural activity was
recorded using multiple electrodes in primary and secondary auditory cortex of macaque
monkeys passively listening to these stimuli. Mutual information between stimulus and neural
activity was characterized using previously established approaches [2,3].
We found that the precise time scale of each code depends on the acoustic stimulus. For binary
spike words (spike timing), the temporal precision required to decode maximal information
was higher during stimulation with random tones (average 7 ms) than with natural
sounds (average 12 ms). In addition, the degree to which field potentials were stimulus
locked (‘entrained’) varied between sound types: during stimulation with random tones entrainment
was stronger and extended to much higher frequencies (up to 60Hz) than during
stimulation with natural sounds (about 30 Hz).
These results extend previous finding in the visual thalamus and demonstrate that the temporal
precision of sensory neurons responses in auditory cortex depends on the temporal
structure of the stimulus. In particular, stimuli with shorter correlation times, hence faster intrinsic
time scales, induce responses that vary on shorter time scales. This implies that the
relevant time scales of neural codes are not fixed, but are dynamically adapted to, or reflect
the environment.},
web_url = {http://www.areadne.org/2010/home.html},
editor = {Hatsopoulos, N. G., S. Pezaris},
event_name = {AREADNE 2010: Research in Encoding And Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Poster{ GoenseML2010,
title = {Detectability of the BOLD signal},
year = {2010},
month = {5},
volume = {2010},
number = {1189},
abstract = {The BOLD signal is a weak signal, and hence if no BOLD signal is found in an area this does not automatically mean there is no neural activity in that area. Signal dropout, artifacts, instability, physiological noise, RF-coil inhomogeneity etc. can all reduce the SNR locally leading to decreased detectability of the BOLD signal. Here we illustrate that calculation of the spatial distribution of the detection thresholds allows us to assign a degree of confidence to the activations as well as identify areas where detectability of functional activation is compromised.},
file_url = {fileadmin/user_upload/files/publications/ISMRM-2010-1189_6536.pdf},
web_url = {http://www.ismrm.org/meetings-workshops/2010-annual-meeting-3/},
event_name = {ISMRM-ESMRMB Joint Annual Meeting 2010},
event_place = {Stockholm, Sweden},
state = {published},
author = {Goense J{jozien}{Department Physiology of Cognitive Processes}, Merkle H{hellmut} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ ParkesHALP2010,
title = {High resolution tractography in macaque visual system: validation against in vivo tracing},
year = {2010},
month = {5},
volume = {2010},
number = {118},
abstract = {Structural connectivity patterns are important for understanding brain function. Diffusion imaging offers the possibility of determining in vivo
connections in the human brain. Validation of this technique is important, but has proved difficult due to lack of an adequate gold standard1. The aim of this work is to use the macaque visual system as a model, in which true connections are well-known due to many detailed in vivo tracer studies2. High angular resolution diffusion
imaging (HARDI) of the post-mortem macaque brain, and a probabilistic tractography approach is used, and comparisons are made between identified connections at
different thresholds of connection strength, and known connections from detailed visual system wiring map first described in detail by Felleman & van Essen8. 72% of
connections were correctly identified.},
file_url = {fileadmin/user_upload/files/publications/ISMRM-2010-118.PDF},
web_url = {http://www.ismrm.org/10/},
event_name = {ISMRM-ESMRMB Joint Annual Meeting 2010},
event_place = {Stockholm, Sweden},
state = {published},
author = {Parkes LM, Haroon HA, Augath M{mark}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Parker GJ}
}

@Poster{ KirschASSS2010,
title = {In vivo chlorine-35, sodium-23 and proton magnetic resonance imaging of the rat brain},
year = {2010},
month = {5},
volume = {2010},
number = {981},
abstract = {Chloride (Cl-) is the most abundant anion in the mammal organism playing an important role in many cellular processes. For instance, plasma
membrane Cl- currents are important for the regulation of excitability in nerve and muscle. Moreover, Cl- ions play a crucial role in controlling the
ionic composition of the cytoplasm and the volume of cells [1]. In order to investigate the feasibility of combined in vivo 35Cl, 23Na and 1H MRI we
developed a rf coil setup to measure 35Cl, 23Na and 1H signals in one scanning session without moving the subject or changing the setup.},
file_url = {fileadmin/user_upload/files/publications/ISMRM-2010-981.PDF},
web_url = {http://www.ismrm.org/10/},
event_name = {ISMRM-ESMRMB Joint Annual Meeting 2010},
event_place = {Stockholm, Sweden},
state = {published},
author = {Kirsch S, Augath M{mark}{Department Physiology of Cognitive Processes}, Seiffge D, Schilling R and Schad LR}
}

@Poster{ RoseMHELLP2010,
title = {Piconmat.com version 2.0: A Web-based Probabilistic Tractography Data Service},
year = {2010},
month = {5},
volume = {2010},
number = {1666},
abstract = {We are developing web-based software to provide diffusion MRI-derived in vivo information about
the connections between cortical regions in human and animal subjects, and present the latest version of our software,
piconmat.com version 2.0. By measuring the diffusivity of water along white matter fibre bundles, diffusion MRI
and probabilistic tractography allow in vivo inferences to be made about the presence of connections between regions of
the brain1. Tractography results are useful to a range of communities, from those working in MR, through biologists,
psychologists and physicians. However, tractography requires access to MR scanning facilities, and the use of
appropriate MR sequences and tractography software. To answer many questions of interest it is necessary to
characterise connectivity with respect to a population of subjects and across species. For many investigators, such
experiments are impractical. One approach is to provide anatomical connection information online, e.g., the CoCoMac
database summarises over 400 literature reports on invasive tracer experiments on macaques2. These methods are an
accepted gold standard, but cannot be used in humans. In vivo HARDI-based approaches do not suffer from this
drawback. Fig. 1 illustrates a typical tractography result. Version 2.0 of piconmat.com improves substantially upon
the previous version that debuted at the 2009 ISMRM meeting. WEB-BASED INTERFACE Conventionally, the
strength of connection between all pairs of cortical regions is represented as a symmetrical matrix, which can be visualised as a colour-coded array plot. Our software is
based around an interactive connection matrix (Fig. 2), which displays the mean connection strengths between all pairs of regions, where the averaging is performed
over all individuals in the piconmat.com dataset that meet certain criteria. As the user moves the mouse across the connection matrix, a display is updated to show
information about the corresponding region pair; this includes: the names of the regions, the mean connection strength, and a coarse histogram of the distribution of
strengths. The information about a region pair can be added to a list by clicking on that region pair’s matrix element. Associated with each individual is certain metadata
(e.g., age, sex, handedness). Controls are provided to allow the user to include or exclude individuals on the basis of these characteristics; the connection matrix and list
of selected regions update to reflect changes in the set of individuals of interest. Multiple connection matrices can be simply added to the page, such that visual
comparisons of the connection strengths between groups—e.g., males and females aged 25–50—can be made. Finally, once information about interesting region pairs
has been selected, the underlying data can be obtained in a format that can be copied and pasted into Excel or statistics software for further analysis. ACQUISITION &
TRACKING For the human brain data held at piconmat.com, high angular resolution diffusion data were acquired in human volunteers on a 3T Philips Achieva
scanner using an 8-element head coil. PGSE EPI with TE=59ms, cardiac gating, Gmax=62mT/m, partial Fourier factor 0.679, 112×112 matrix reconstructed to 128×128,
reconstructed resolution 1.875×1.875mm2, slice thickness 2.1mm, 60 contiguous slices, 61 directions at b=1200s/mm2, 1 at b=0, SENSE factor = 2.5, correction for
susceptibility and eddy current-induced distortion3. Tractography connection maps were produced between the aparc+aseg regions defined by FreeSurfer4,5, using the
multi-fibre Probabilistic Index of Connectivity (PICo) method6. At each voxel, diffusion probability density functions—generated using constrained spherical
deconvolution and a model-based residual bootstrapping method7,8—describe fibre bundle orientation uncertainty. We used 1000 streamlines and a step size of 0.5mm.
Streamlines were terminated on doubling back or on leaving the brain volume. A voxel’s connection is defined as the proportion of all streamlines that pass through it.
DISCUSSION & CONCLUSIONS We have outlined a significant enhancement to previously reported software, piconmat.com, which we have made publicly
available at no cost, as a service to the scientific community. The software uses standard web technologies (HTTP, XHTML, CSS and JavaScript) and requires a highperformance
modern browser such as Mozilla Firefox v3.5, Apple Safari v4, Opera v10 or Google Chrome v3. Future work will include improving performance under
Microsoft Internet Explorer, the addition of more connection data, and releasing the source code under an open source license. ACKNOWLEDGEMENTS Financial
support has been provided by the UK’s BBSRC (BB/E002226/1), EPSRC (GR/T02669/01) and MRC (G0501632). REFERENCES 1 Johansen-Berg et al. Curr Opin
Neurol, 2006:19;379–85. 2 Stephan et al. Phil Trans Roy Soc Series B, 2001:356;1159–86. 3 Embleton et al. Proc ISMRM #1070, 2006. 4 Fischl et al. Cerebral Cortex,
2008:18;1973–80. 5 Yeo et al. Med Imag Anal, 2008:12;603–15. 6 Parker et al. Phil Trans Roy Soc Series B, 2005:360;893–902. 7 Haroon et al. IEEE TMI,
2009:28;535–50. 8 Haroon et al. Proc ISMRM #362, 2009.},
file_url = {fileadmin/user_upload/files/publications/ISMRM-2010-1666.PDF},
web_url = {http://www.ismrm.org/10/},
event_name = {ISMRM-ESMRMB Joint Annual Meeting 2010},
event_place = {Stockholm, Sweden},
state = {published},
author = {Rose CJ, Morris D, Haroon H, Emleton K, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Lambon Ralph M and Parker GJ}
}

@Poster{ BiessmannMBVKMR2010,
title = {Comparison of V1 receptive fields mapped with spikes and local field potentials},
journal = {Frontiers in Neuroscience},
year = {2010},
month = {2},
volume = {Conference Abstract: Computational and Systems Neuroscience 2010},
abstract = {Extracellular neurophysiological recordings are typically separated in two frequency bands. Low frequency content, also called local field potentials (LFPs), reflect subthreshold integrative processes of a population of neurons. High frequency content, or multi-unit activity (MUA), contains the information conveyed by action potentials, or spikes. Spikes reflect neuronal output and are generally considered as the main currency of information in the brain. For a long time receptive field mapping methods have focused exclusively on spiking information, although some recent studies have begun to address spatial characterstics of LFP responses (Xing/Yeh/Shapley, 2009, J Neurosci). In order to compare the information about visual stimuli carried by the LFP signal and spiking activity we mapped receptive fields in primary visual cortex of the tree shrew using spike count and LFP timeseries recorded at different cortical depths. We presented white noise checkerboard patterns and sparse noise patterns and computed the standard spike triggered average (STA) receptive fields. Moreover we extracted the LFP timeseries, in different frequency bands, and the spike histograms following each stimulus and computed receptive fields for each signal employing standard canonical correlation analysis (CCA) between stimulus and LFP and spike response, respectively. Receptive fields as estimated from LFP data have two main advantages over traditional STA estimates. For one, LFP receptive fields do not suffer from binning artefacts, in contrast to STA receptive fields. Besides, CCA allows for computing a temporal filter for the respective neural signal. Receptive fields estimated using spikes were very similar to those computed from LFP signals, also for LFP bands below 20Hz. In particular the spatial extent of receptive fields computed from LFPs was comparable to that of spikes, in line with previous studies reporting a small spatial focus of LFP selectivity (Katzner et al. 2009, Neuron, Xing/Yeh/Shapley, 2009, J Neurosci). The receptive field size of both LFP and spikes varied with cortical depth. In summary our results confirm that in early stages of the visual processing hierarchy LFP signals contain to a large extent the same information about the visual stimulus as the spiking activity. In line with the above mentioned studies on non-human primates our findings suggest that the spatial selectivity of LFP signals with respect to the visual stimulus is comparable to that of spikes.},
web_url = {http://www.frontiersin.org/10.3389/conf.fnins.2010.03.00101/event_abstract},
event_name = {Computational and Systems Neuroscience Meeting (COSYNE 2010)},
event_place = {Salt Lake City, UT, USA},
state = {published},
DOI = {10.3389/conf.fnins.2010.03.00101},
author = {Biessmann F{fbiessma}{Department Physiology of Cognitive Processes}, Meinecke F, Bhattacharyya A{anwesha}{Department Physiology of Cognitive Processes}, Veit J{jveit}{Department Physiology of Cognitive Processes}, Kretz R, M\"uller K-R{klaus}{Department Empirical Inference} and Rainer G{gregor}}
}

@Thesis{ Gotthardt2010,
title = {Neurophysiologische Studien zu raumzeitlichen Mustern induzierter und evozierter Oszillationen},
year = {2010},
month = {7},
file_url = {fileadmin/user_upload/files/publications/Thesis_Sascha_Gotthardt_Final.pdf},
state = {published},
type = {PhD},
author = {Gotthardt S{gotthardt}{Department Physiology of Cognitive Processes}}
}

@Thesis{ Rulla2010,
title = {Beta Band Modulation in correct and false motor performance},
year = {2010},
month = {6},
state = {published},
type = {Master},
author = {Rulla S{rulla}}
}

@Conference{ Aggelopoulos2010_2,
title = {The representation of objects in the inferior temporal cortex of the macaque monkey},
year = {2010},
month = {12},
day = {9},
event_name = {Max Planck Institute for Brain Research},
event_place = {Frankfurt a. M., Germany},
state = {published},
author = {Aggelopoulos N{aggelopoulos}{Department Physiology of Cognitive Processes}}
}

@Conference{ Aggelopoulos2010,
title = {Commercially available spike sorting software},
year = {2010},
month = {12},
day = {2},
event_name = {Workshop "Tetrode recording and spike sorting", Max Planck Institute for Biological Cybernetics},
event_place = {Tübingen, Germany},
state = {published},
author = {Aggelopoulos N{aggelopoulos}{Department Physiology of Cognitive Processes}}
}

@Conference{ 7057,
title = {A brain region consisting of neurons with moderate sensitivity for voices},
year = {2010},
month = {11},
volume = {40},
number = {125.3},
abstract = {A region of "voice" clusters has recently been identified in the macaque auditory cortex with functional magnetic-resonance imaging (fMRI). These clusters show a strong fMRI activity preference for the voice of conspecifics and appear to functionally correspond to those from the known human voice region. In the visual system fMRI has been used to guide electrophysiological recordings from neurons in the monkey brain that were shown to be highly selective for faces [1]. We investigated whether fMRI-guided electrophysiology would reveal comparable levels of selectivity in one of the recently identified monkey voice clusters [2]. During fMRI acquisition and electrophysiological recordings, three categories of 12 sounds were used for stimulation: macaque vocalizations (MVocs), other animal vocalizations (AVocs), and natural sounds (NSnds). The sound categories were comparable in their low-level acoustical features, having been selected for this from a large set of sounds. We first used the stimuli during fMRI, as we have previously done, to identify the clusters with a strong activity preference for MVocs. Then electrophysiological responses to the auditory stimuli were recorded from the anterior voice cluster in two awake macaques (total of 193 responsive single- and multi-units, from 125 sites). Both monkeys showed moderate neuronal response preferences for MVocs over the other sound categories (respectively, 41% and 29% preference for MVocs in the unit activity of each animal), even if the analysis focused on the focal cluster in each animal with maximal selectivity for MVocs (respectively, 72% and 73% preference for MVocs). Our results suggest that a strong fMRI activity preference need not result from a large proportion of highly selective neurons. This is the case even if methodological differences may have somewhat affected the neuronal selectivity differences observed between our study and the previous macaque work on face processing, which resulted in 96% and 84% selectivity for faces in two animals [1]. In all cases, our results may reflect evolutionary differences that have affected voice and face selectivity. Namely, the visual system appears to have specialized during vertebrate evolution to represent canonical facial features (e.g., two eyes, a nose and a mouth). By contrast, the auditory system could have had less opportunity to specialize, given that many animals modify the acoustics of their vocalizations to be distinct from those of other animals and to circumvent environmental noise.},
file_url = {fileadmin/user_upload/files/publications/2011/Neuroscience-2010-Perrodin.pdf},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Perrodin C{cperrodin}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Petkov CI{chrisp}}
}

@Conference{ 7058,
title = {Visual influences on voice-sensitive neurons},
year = {2010},
month = {11},
volume = {40},
number = {125.4},
abstract = {Many animals depend upon vocal and facial communication signals for survival and social interactions, but it remains unclear how voices and faces are integrated by the brain. Most studies have evaluated the unisensory processing of either vocal or facial information in brain
regions thought to be "voice" or "face" sensitive. Other studies have described multisensory interactions in the brain for voices and faces, but only for a few brain regions, such as those close to the primary auditory cortex or in the prefrontal cortex. This work aims to address whether the responses of neurons in a voice-sensitive brain region, which was recently identified in monkeys with functional MRI, are influenced by faces.
Extracellular recordings were conducted in two awake rhesus macaques. We targeted the anterior voice-sensitive cluster on the superior temporal plane, which was first localized for each animal with fMRI [please see the linked presentation] and resides ~5 mm anterior to the tonotopically organized field RT. For stimulation we used movies of vocalizing monkeys and humans that were matched in their low-level auditory and visual features. These dynamic face and voice stimuli were presented in auditory only, visual only or audio-visual stimulation conditions.
Neuronal responses to the stimuli yielded a total of 318 local-field potential (LFP) sites and 208 single- and multi-units. Significant multisensory interactions were observed in 70% of the LFP sites and in 33% of the single- and multi-unit responses. We observed both suppression and
enhancement of the neuronal responses to the audio-visual condition compared to the auditory condition, as previously noted for neurons in other brain regions. Notably, human voices were as efficient in driving the neuronal responses as were the monkey voices and elicited similar audiovisual interactions, questioning the species-specificity of the voice-sensitive regions.
Our results provide evidence for visual influences in what has been characterized as an auditory "voice" region. This suggests that, rather than conducting strictly unisensory processing, neurons in the voice region (and potentially also the face region) form an integral part of a network
engaged in the processing of communication signals from the different sensory modalities.},
file_url = {fileadmin/user_upload/files/publications/2011/Neuroscience-2010-Perrodin-2.pdf},
web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main},
event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)},
event_place = {San Diego, CA, USA},
state = {published},
author = {Perrodin C{cperrodin}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Petkov CI{chrisp}}
}

@Conference{ BiessmannMMLM2010,
title = {Comparison of Mass-Univariate, Unimodal and Multivariate Multimodal Analysis Methods for Neurovascular Coupling Analysis},
journal = {Frontiers in Computational Neuroscience},
year = {2010},
month = {10},
volume = {Conference Abstract: Bernstein Conference on Computational Neuroscience},
abstract = {In the past years multimodal brain imaging methods have yielded valuable insights into how functional
magnetic resonance imaging (fMRI) signals are related to the underlying neural activity. However,
the rapid advances in multimodal imaging technology were not accompanied by the development of
appropriate analysis methods for multimodal data. We present a multimodal analysis framework, temporal kernel Canonical Correlation Analysis (tkCCA) [1,2], and show how it can be used to analyse the spatio-temporal and time-frequency correlation structure between simultaneously measured intracortical neurophysiological recordings and high dimensional fMRI signals. Given the spectrograms of neurophysiological activity and the simultaneously recorded fMRI data we estimate a convolution linking di_erent bands of neural bandpower to an activity pattern of fMRI signals. The convolution can be interpreted as the pattern in time-frequency and time-voxel space that maximises the canonical correlation [3] between neural and haemodynamic activity.
We show results from data recorded in primary visual cortex during spontaneous activity and during visual stimulation. The analysis resulted in robust neurovascular coupling patterns across different experimental conditions. We compared the multivariate patterns with univariate coupling measures and spatial principal component analysis (SPCA) by measuring the accuracy when predicting neural activity from BOLD signals. Our _ndings suggest that the _lters estimated by tkCCA predict neural activity better than univariate methods and unimodal methods such as SPCA.},
web_url = {http://www.frontiersin.org/10.3389/conf.fncom.2010.51.00075/event_abstract},
event_name = {Bernstein Conference on Computational Neuroscience 2010},
event_place = {Berlin, Germany},
state = {published},
DOI = {10.3389/conf.fncom.2010.51.00075},
author = {Biessmann F{fbiessma}{Department Physiology of Cognitive Processes}, Meinecke FC, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and M\"uller KR{klaus}{Department Empirical Inference}}
}

@Conference{ KayserPL2010,
title = {Decoding complex sounds from auditory cortex responses without knowledge of precise stimulus timing},
journal = {Frontiers in Computational Neuroscience},
year = {2010},
month = {10},
volume = {Conference Abstract: Bernstein Conference on Computational Neuroscience},
abstract = {Sensory systems can recognize complex stimuli even when these appear at unexpected times. While much work quantifies the stimulus information carried by neural responses, most studies measure spike times with respect to a stimulus-related time frame, and thus implicitly assume a precise ‘clock’ registering the timing of sensory and neural events (Panzeri TINS 10). However, sensory systems may not have such a clock, and likely rely on intrinsic mechanisms to measure the timing of sensory and neural events.

This raises the questions of how well different sensory stimuli can be discriminated in the absence of a perfect clock, and what neural codes could mediate ‘clock-free’ sensory representations. Addressing these questions, we used the primate auditory cortex as a model system and investigated the information carried by different putative neural codes that do not rely on the precise knowledge of stimulus timing.

Our approach builds on the observation that in auditory cortex theta rhythm network activity is entrained by complex sounds (Kayser Neuron 09). As such, the phase of slow rhythms can serve as an intrinsic temporal frame of reference. We show that a spike pattern code based on inter-spike interval (ISI) distributions can discriminate different complex sounds, and does so significantly better when referenced to the local theta rhythm. More specifically, we used 200 ms long sliding windows to mimic uncertainty about stimulus onset, and within each window discriminated different naturalistic sounds using either spike counts, ISI distributions and combined ISI and theta-phase distributions. The combined ISI-phase code provided about a 50% increase of stimulus-related information compared to spike counts. These results suggest that combining different intrinsic time scales, such as ISI’s and slow rhythms, allows the construction of neural codes that carry considerable information about sensory stimuli without making reference to the timing of external events.},
web_url = {http://www.frontiersin.org/10.3389/conf.fncom.2010.51.00008/event_abstract},
event_name = {Bernstein Conference on Computational Neuroscience 2010},
event_place = {Berlin, Germany},
state = {published},
DOI = {10.3389/conf.fncom.2010.51.00008},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Panzeri S{stefano} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ MazzonikMMQLP2010,
title = {Neurons in primary visual cortex encode naturalistic visual information using multiple temporal scales},
journal = {Frontiers in Computational Neuroscience},
year = {2010},
month = {10},
volume = {Conference Abstract: Bernstein Conference on Computational Neuroscience},
abstract = {Natural stimuli have a rich temporal structure, yet it is still unclear whether the encoding of such stimuli employs more than one response time scale. To investigate this issue, we analyzed the activity of neurons recorded in primary visual cortex of anesthetized macaques during presentation of naturalistic movies, and we quantified the amount of information carried by neural codes operating at different temporal scales. We divided the recording time into stimulus windows of tens of ms, and computed the information carried by the neural response about which stimulus window was being shown. Within each time window, responses were quantified using either the spike count, or using binary spike patterns, defined by the absence/presence of spikes within short time bins (t). We found that temporal spike patterns with precision t of 8 or 16 ms provided more stimulus information than spike counts, but this information gain did not increase further when reducing the bins size t. This suggests a response precision of single neurons on the scale of 8ms. In addition, we found that the joint knowledge of spike patterns and the phase of low frequency LFPs at which these patterns occurred - computed as in (Kayser et al. Neuron 2009) - carried more information than either code considered by itself. This suggests that the information carried by slow LFP fluctuations complements that carried by spike patterns.
In summary, we found evidence for complementary response time scales for the encoding of naturalistic stimuli in visual cortex. Informative codes range from spike timing precision at about 10 ms resolution to the much coarser phase of firing with respect to low frequency fluctuations. These findings indicate that sensory cortices may enhance their information capacity by multiplexing complementary information at different time scales.},
web_url = {http://www.frontiersin.org/10.3389/conf.fncom.2010.51.00101/event_abstract},
event_name = {Bernstein Conference on Computational Neuroscience 2010},
event_place = {Berlin, Germany},
state = {published},
DOI = {10.3389/conf.fncom.2010.51.00101},
author = {Mazzoni A, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Martinez J{jmartinez}, Quiroga RQ, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Conference{ 7083,
title = {The effects of TMS over the parietal cortex on binocular rivalry},
year = {2010},
month = {10},
volume = {11},
pages = {14},
abstract = {Human fMRI studies of binocular rivalry and other bistable phenomena suggest that a network of frontal and parietal areas, predominantly in the right hemisphere, is particularly involved during switches between the two conflicting percepts. However, these studies do not provide information about causality, i.e. whether fMRI activity is a consequence or a cause of the perceptual change. In the current study we localized areas that were activated
during perceptual switches in individual subjects using fMRI. We then tested the effect of disturbing neural processing in two distinct parietal regions along the ventral-dorsal axis in both hemispheres using 2 Hz repetitive transcranial magnetic stimulation (TMS). Our results show that on the group level, TMS over the right intraparietal sulcus (IPS) prolonged the periods of stable percepts. In individual subjects, the IPS in the hemisphere with higher fMRI activation also showed a stronger TMS effect, as reflected in the positive correlation between
the lateralization of TMS effects and that of fMRI activations. Our results thus demonstrate a causal, de-stabilizing effect of the IPS on perceptual continuity and provide a direct link between correlational and causal measures of cortical function during conscious perception.},
web_url = {http://www.neuroschool-tuebingen-nena.de/fileadmin/user_upload/Dokumente/neuroscience/AbstractbookNeNa2010u.pdf},
event_name = {11th Conference of Junior Neuroscientists of Tübingen (NeNa 2010)},
event_place = {Heiligkreuztal, Germany},
state = {published},
author = {Zaretskaya N{nataliya}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6774,
title = {The behavioral hallmarks of face processing in humans and macaques - an eye tracking investigation},
year = {2010},
month = {9},
day = {14},
abstract = {An essential characteristic of primates is social cognition. Social cognition is an evolutionary result of living in social systems. Underlying all of the social abilities are the recognition of kin and conspecifics and the analysis of communicational signals, in which one element is crucial: the face. Thus, given the social significance of faces compared to other natural objects, it may appear obvious that the brain processes faces differently than non-face objects. The question to what extent faces are processed differently when compared to non-face object has been a major focus of research in human for the past several decades. The behavioral hallmarks of face perception (holistic face perception and subordinate-level entry point) as well as the underlying neural mechanisms have been studied extensively in humans. Relatively little is known so far about the behavioral abilities with respect to face perception in the macaque, while the neural signal derived from single cell recordings taught us much about t
he aspects of facial selectivity in the brain. Here, critical experimental paradigms, known from the research in humans, were employed in combination with standard eye tracking methods to investigate face processing abilities in macaques and humans. This comparative approach not only demonstrates that macaques and humans employ similar face processing strategies, it also illustrates an effective approach on comparative cognitive research questions.},
web_url = {http://primate-society.com/ips/},
event_name = {International Primatological Society XXIII Congress (IPS 2010)},
event_place = {Kyoto, Japan},
state = {published},
author = {Dahl CD{dahl}{Department Human Perception, Cognition and Action}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6674,
title = {Visual influences on voice-sensitive neurons},
year = {2010},
month = {7},
day = {7},
web_url = {http://www.ncl.ac.uk/ion/news/events/eventitem.htm?id=brown-bag-lunchtime-seminar5},
event_name = {Institute of Neuroscience, Newcastle University Medical School},
event_place = {Newcastle upon Tyne, UK},
state = {published},
author = {Perrodin C{cperrodin}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6681,
title = {Multisensory responses in temporal association cortex},
year = {2010},
month = {7},
day = {1},
event_name = {Karolinska Institute, Department of Neuroscience},
event_place = {Stockholm, Sweden},
state = {published},
author = {Dahl CD{dahl}{Department Human Perception, Cognition and Action}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6811,
title = {Electrical Microstimulation and fMRI},
year = {2010},
month = {6},
volume = {2010},
pages = {34},
abstract = {Electrical stimulation (ES) of the brain has been performed for over 100 years, and although
some might say it is a crude technique for understanding the detailed mechanisms underlying
different neural computations, microstimulation has made significant contributions to our
knowledge in both basic and clinical research. Recently there has been resurgence in its use in
the context of electrotherapy and neural prostheses. For example, ES has made it possible to
at least partially restore hearing to deaf patients by delivering pulses via implanted electrodes
to different regions of the cochlea. Stimulation of the basal ganglia is remarkably effective in
restoring motor function to Parkinson’s patients, and microstimulation of the geniculostriate
visual pathway is regarded by some as a very promising (future) method for making the blind
see again.
Yet, the methodology still suffers from at least two fundamental problems; (a) we do not always
know exactly what is being stimulated when we pass currents through the tissue; and
(b) stimulation causes activation in a large number of areas even outside the stimulation site,
making it difficult to isolate and evaluate the behavioral effects of the stimulated area itself.
Microstimulation during fMRI (esfMRI) could provide a unique opportunity to visualize the networks
underlying electrostimulation-induced behaviors, to map neuromodulatory systems, or
to develop electrotherapy and neural prosthetic devices. Moreover esfMRI is an excellent tool
for the study of the effects of regional synaptic plasticity, e.g. LTP in hippocampus, on cortical
connectivity. Last but not least, esfMRI can offer important insights into the functional
neurovascular coupling. In my talk, I shall discuss findings from recent and on-going work on
signal propagation during electrical stimulation, as well as data related to effective connectivity.},
web_url = {http://www.areadne.org/2010/home.html},
editor = {Hatsopoulos, N. G., S. Pezaris},
event_name = {AREADNE 2010: Research in Encoding And Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6432,
title = {The hallmarks of face perception in humans and monkeys},
year = {2010},
month = {4},
day = {12},
event_name = {Eötvös Lorand University, Department of Ethology},
event_place = {Budapest, Hungary},
state = {published},
author = {Dahl CD{dahl}{Department Human Perception, Cognition and Action}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6381,
title = {Neurobiologische Grundlagen menschlicher Bindung},
year = {2010},
month = {3},
day = {14},
event_name = {Staatstheater Stuttgart, öffentliche Expertenrunde},
event_place = {Stuttgart, Germany},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6380,
title = {Cortial Regions Distinguishing Self-motion Cues from Object Motion Cues},
year = {2010},
month = {2},
day = {22},
web_url = {http://www.cin.uni-tuebingen.de/fileadmin/pdfs/Events/Broschuere_fin-1_Giese.pdf},
event_name = {Symposium "Neural Encoding of Perception and Action"},
event_place = {Tübingen, Germany},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ Viswanathan2010,
title = {Does bold fMRI reveal pseudo neuronal activity?},
year = {2010},
month = {2},
day = {1},
web_url = {http://www.gla.ac.uk/events/?action=details&id=5104},
event_name = {Center for Cognitive Neuroimaging, University of Glasgow},
event_place = {Glasgow, UK},
state = {published},
author = {Viswanathan A{ahalya}{Department Physiology of Cognitive Processes}}
}

@Conference{ KayserLP2010,
title = {Visual influences on information representations in auditory cortex},
journal = {Frontiers in Neuroscience},
year = {2010},
month = {2},
volume = {Conference Abstract: Computational and Systems Neuroscience 2010},
abstract = {Combining information across different sensory modalities can greatly facilitate our ability to detect or recognize sensory stimuli. Recent work demonstrates that sensory integration is a distributed process, commencing in lower sensory areas and continuing in higher association cortices. Here we investigate the impact that visual stimuli have on the representation of sounds in auditory cortex. To this end we analyze neural responses to naturalistic audio-visual stimuli recorded while monkeys perform a visual fixation task. To characterize multisensory influences we quantify stimulus information provided by different putative neural codes. In particular, we have previously shown (Kayser et al. Neuron 09) that neural activity in auditory cortex is stimulus related on multiple temporal scales, including slow modulation of firing rates, millisecond precise temporal spike patterns and the relative timing of spiking activity to slow (<10Hz) ongoing network activity (phase-of-firing). In the context of multisensory stimuli, we find (Kayser et al. Curr Biol. In Press) that visual stimulation renders spiking responses more reliable across trials (repeats of the same stimulus), and more reliable in time (temporal precision of spikes). This increased reliability enhances the stimulus information provided by neural activity on slow (firing rate) and fast (spike patterns) time scales. As shown by feature extraction, this information gain pertains mostly to temporal sound properties, such as sound envelope, and is much reduced when incongruent visual and auditory stimuli are presented. Overall, these results demonstrate that multisensory influences enhance sensory representations already at early stages in cortex, and do so by enhancing the reliability of stimulus representations on multiple time scales.},
web_url = {http://www.frontiersin.org/10.3389/conf.fnins.2010.03.00021/event_abstract},
event_name = {Computational and Systems Neuroscience Meeting (COSYNE 2010)},
event_place = {Salt Lake City, UT, USA},
state = {published},
DOI = {10.3389/conf.fnins.2010.03.00021},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Conference{ 6378,
title = {Über die Neurobiologie der Liebe},
year = {2010},
month = {1},
day = {26},
event_name = {Studium Generale, Universität Freiburg},
event_place = {Freiburg, Germany},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6379,
title = {Über die Neurobiologie des Glücks},
year = {2010},
month = {1},
day = {9},
event_name = {Jahrestagung Forum für Organisationsentwicklung Schweiz},
event_place = {Rigi-Kulm, Schweiz},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ Logothetis2010_3,
title = {Neurovascular coupling: insights from physiology, neuropharmacology & electrical microstimulation},
journal = {Frontiers in Neuroscience},
year = {2010},
month = {1},
volume = {Conference Abstract: IBRO International Workshop 2010},
abstract = {BOLD fMRI is currently the mainstay of neuroimaging in cognitive neuroscience. Advances in scanner technology, image acquisition protocols, experimental design, and analysis methods promise to push forward fMRI from mere cartography to the true study of brain organization. However, fundamental questions concerning the interpretation of fMRI data abound, as the conclusions drawn often ignore the actual limitations of the methodology.
In my talk I shall describe our current understanding of the neurophysiological and hemodynamic signals, and of the structural and functional neurovascular coupling in the anesthetized and alert behaving monkey. Over the last ten years we have been studying the neurovascular coupling by means of simultaneous physiological and fMRI experiments, neuropharmacology, with micro-sampling and mass spectrometry, as well as with combined electrical microstimulation and fMRI (esfMRI). Our findings together with those from other laboratories suggest that the limitations of fMRI are mainly due to the circuitry and functional organization of the brain, as well as to inappropriate experimental protocols that ignore this organization. Our current knowledge of cortical microcircuits, inhibition, neuromodulation, and glia cell activity suggests that fMRI can be used as an excellent tool for formulating intelligent, data-based hypotheses, but only in certain special cases can it be useful for unambiguously selecting one of them, or for explaining the detailed neural mechanisms underlying the studied cognitive capacities. In the vast majority of cases, it is the combination of fMRI with other techniques and the parallel use of animal models that will be the most effective strategy for understanding brain function.},
web_url = {http://www.frontiersin.org/10.3389/conf.fnins.2010.10.00204/event_abstract},
event_name = {IBRO International Workshop 2010},
event_place = {Pécs, Hungary},
state = {published},
DOI = {10.3389/conf.fnins.2010.10.00204},
author = {Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 6239,
title = {Long-Term Stability of Visual Pattern Selective Responses of Monkey Temporal Lobe Neurons},
journal = {PLoS One},
year = {2009},
month = {12},
volume = {4},
number = {12},
pages = {1-10},
abstract = {Many neurons in primate inferotemporal (IT) cortex respond selectively to complex, often meaningful, stimuli such as faces and objects. An important unanswered question is whether such response selectivity, which is thought to arise from experience-dependent plasticity, is maintained from day to day, or whether the roles of individual cells are continually reassigned based on the diet of natural vision. We addressed this question using microwire electrodes that were chronically implanted in the temporal lobe of two monkeys, often allowing us to monitor activity of individual neurons across days. We found that neurons maintained their selectivity in both response magnitude and patterns of spike timing across a large set of visual images throughout periods of stable signal isolation from the same cell that sometimes exceeded two weeks. These results indicate that stimulus-selectivity of responses in IT is stable across days and weeks of visual experience.},
web_url = {http://www.plosone.org/article/fetchObjectAttachment.action?uri=info%3Adoi%2F10.1371%2Fjournal.pone.0008222&representation=PDF},
state = {published},
DOI = {10.1371/journal.pone.0008222},
EPUB = {e8222},
author = {Bondar IV{igor}{Department Physiology of Cognitive Processes}, Leopold DA{davidl}{Department Physiology of Cognitive Processes}, Richmond BJ, Victor JD and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5641,
title = {Multisensory interactions in primate auditory cortex: fMRI and electrophysiology},
journal = {Hearing Research},
year = {2009},
month = {12},
volume = {258},
number = {1-2},
pages = {80-88},
abstract = {Recent studies suggest that cross-modal integration does not only occur in higher association cortices but also in early stages of auditory processing, possibly in primary or secondary auditory cortex. Support for such early cross-modal influences comes from functional magnetic resonance imaging experiments in humans and monkeys. However we argue that the current understanding of neurovascular coupling and of the neuronal basis underlying the imaging signal does not permit the direct extrapolation from imaging data to properties of neurons in the same region. While imaging can guide subsequent electrophysiological studies, only these can determine whether and how neurons in auditory cortices combine information from multiple modalities. Indeed, electrophysiological studies only partly confirm the findings from imaging studies. While recordings of field potentials reveal strong influences of visual or somatosensory stimulation on synaptic activity even in primary auditory cortex, single unit studies find only
a small minority of neurons as being influenced by non-acoustic stimuli. We propose the analysis of the information coding properties of individual neurons as one way to quantitatively determine whether the representation of our acoustic environment in (primary) auditory cortex indeed benefits from multisensory input.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T73-4VSB18D-2-C&_cdi=5047&_user=29041&_orig=search&_coverDate=03%2F06%2F2009&_sk=999999999&view=c&wchp=dGLbVlW-zSkzk&md5=c2454278adededccb8c1313ff960fd5c&ie=},
state = {published},
DOI = {10.1016/j.heares.2009.02.011},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Petkov CI{chrisp} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ WangLL2009,
title = {Spatiotemporal Neural Integration for Bistable Perception in a Response-Time Structure-From-Motion Task},
journal = {IEEE Transactions on Biomedical Engineering},
year = {2009},
month = {12},
volume = {56},
number = {12},
pages = {2937-2948},
abstract = {The question of how perception arises from neuronal activity in the visual cortex is of fundamental importance to many issues in cognitive neuroscience. To address this question, we adopt a unique experimental paradigm in which bistable stimuli, namely structure from motion (SFM), are employed to dissociate the visual input from perception while monitoring cortical neural activity. In this paper, we analyze the dynamic responses of the multiunit activity, simultaneously collected from multiple channels in the middle temporal visual cortex of awake behaving macaque monkeys, for decoding the bistable percepts of SFM in a response-time (RT) perceptual discrimination task. Our goal is to understand how the perceptual discriminative information of neuronal population activity evolves and accumulates over time to mediate behaviors. Here, we used a discriminative classifier called the logistic regression and contrasted it with two generative classifiers, namely the quadratic discriminant analysis (QDA) and linear discriminant analysis (LDA), to achieve the spatiotemporal integration of neural activity and dynamically decode the perceptual reports on a single-trial basis. We found that the logistic regression outperforms both QDA and LDA in terms of decoding accuracy for both single-channel and multichannel decoding of bistable percepts. Subsequent analysis of the temporal profile of neural population decoding in relation to RT revealed that the amplitude and latency of the decoding accuracy are highly correlated with the RT, thus indicating that the monkeys respond faster when the decoding accuracy is higher and has shorter latency. These findings suggest that enhanced neuronal discrimination ability and shortened neuronal discrimination latency may impact monkeys' behaviors.},
web_url = {http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5173580&tag=1},
state = {published},
DOI = {10.1109/TBME.2009.2027332},
author = {Wang Z, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Liang H}
}

@Article{ 6151,
title = {Analyzing Short-Term Noise Dependencies of Spike-Counts in
Macaque Prefrontal Cortex Using Copulas and the Flashlight
Transformation},
journal = {PLoS Computational Biology},
year = {2009},
month = {11},
volume = {5},
number = {11},
pages = {1-13},
abstract = {Simultaneous spike-counts of neural populations are typically modeled by a Gaussian distribution. On short time scales, however, this distribution is too restrictive to describe and analyze multivariate distributions of discrete spike-counts. We present an alternative that is based on copulas and can account for arbitrary marginal distributions, including Poisson and negative binomial distributions as well as second and higher-order interactions. We describe maximum likelihood-based procedures for fitting copula-based models to spike-count data, and we derive a so-called flashlight transformation which makes it possible to move the tail dependence of an arbitrary copula into an arbitrary orthant of the multivariate probability distribution. Mixtures of copulas that combine different dependence structures and thereby model different driving processes simultaneously are also introduced. First, we apply copula-based models to populations of integrate-and-fire neurons receiving partially correlated input and show that the best fitting copulas provide information about the functional connectivity of coupled neurons which can be extracted using the flashlight transformation. We then apply the new method to data which were recorded from macaque prefrontal cortex using a multi-tetrode array. We find that copula-based distributions with negative binomial marginals provide an appropriate stochastic model for the multivariate spike-count distributions rather than the multivariate Poisson latent variables distribution and the often used multivariate normal distribution. The dependence structure of these distributions provides evidence for common inhibitory input to all recorded stimulus encoding neurons. Finally, we show that copula-based models can be successfully used to evaluate neural codes, e.g., to characterize stimulus-dependent spike-count distributions with information measures. This demonstrates that copula-based models are not only a versatile class of models for multivariate distributions of spike-counts, but that those models can be exploited to understand functional dependencies.},
web_url = {http://www.ploscompbiol.org/article/fetchObjectAttachment.action;jsessionid=2CA2529D956A6F1FF7B57FE30F7DF04F?uri=info%3Adoi%2F10.1371%2Fjournal.pcbi.1000577&representation=PDF},
state = {published},
DOI = {10.1371/journal.pcbi.1000577},
EPUB = {e1000577},
author = {Onken A, Gr\"unew\"alder S, Munk MHJ{munk}{Department Physiology of Cognitive Processes} and Obermayer K}
}

@Article{ RaschLK2009,
title = {From Neurons to Circuits: Linear Estimation of Local Field Potentials},
journal = {Journal of Neuroscience},
year = {2009},
month = {11},
volume = {29},
number = {44},
pages = {13785-13796},
abstract = {Extracellular physiological recordings are typically separated into two frequency bands: local field potentials (LFPs) (a circuit property) and spiking multiunit activity (MUA). Recently, there has been increased interest in LFPs because of their correlation with functional magnetic resonance imaging blood oxygenation level-dependent measurements and the possibility of studying local processing and neuronal synchrony. To further understand the biophysical origin of LFPs, we asked whether it is possible to estimate their time course based on the spiking activity from the same electrode or nearby electrodes. We used “signal estimation theory” to show that a linear filter operation on the activity of one or a few neurons can explain a significant fraction of the LFP time course in the macaque monkey primary visual cortex. The linear filter used to estimate the LFPs had a stereotypical shape characterized by a sharp downstroke at negative time lags and a slower positive upstroke for positive time lags. The filter was similar across different neocortical regions and behavioral conditions, including spontaneous activity and visual stimulation. The estimations had a spatial resolution of ∼1 mm and a temporal resolution of ∼200 ms. By considering a causal filter, we observed a temporal asymmetry such that the positive time lags in the filter contributed more to the LFP estimation than the negative time lags. Additionally, we showed that spikes occurring within ∼10 ms of spikes from nearby neurons yielded better estimation accuracies than nonsynchronous spikes. In summary, our results suggest that at least some circuit-level local properties of the field potentials can be predicted from the activity of one or a few neurons.},
web_url = {http://www.jneurosci.org/content/29/44/13785.full.pdf+html},
state = {published},
DOI = {10.1523/​JNEUROSCI.2390-09.2009},
author = {Rasch M{rasch}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kreimann G}
}

@Article{ 6146,
title = {Phase Resetting as a Mechanism for Supramodal Attentional Control},
journal = {Neuron},
year = {2009},
month = {11},
volume = {64},
number = {3},
pages = {300-302},
abstract = {Attentional modulation and cross-modal integration might partly rely on the same neurophysiological mechanisms. As a new study by Lakatos et al. in this issue of Neuron shows, attended stimuli in one sensory modality not only modulate oscillatory activity within the primary cortex of the same modality but also reset the phase of ongoing oscillations in primary cortices of other modalities.},
web_url = {http://www.sciencedirect.com/science?_ob=PdfDownloadURL&_uoikey=B6WSS-4XNN3XH-4&_tockey=%23toc%237054%232009%23999359996%231558208%23FLA%23&_orig=search&_acct=C000003178&_version=1&_userid=29041&md5=d3a19b22ecf65ef40852acb5307f1456},
state = {published},
DOI = {10.1016/j.neuron.2009.10.022},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ 6063,
title = {Frequency-Band Coupling in Surface EEG Reflects Spiking Activity in Monkey Visual Cortex},
journal = {Neuron},
year = {2009},
month = {10},
volume = {64},
number = {2},
pages = {281-289},
abstract = {Although the electroencephalogram (EEG) is widely used in research and clinical settings, its link to the underlying neural activity during sensory processing remains poorly understood. To investigate this, we made simultaneous recordings of surface EEG, intracortical local field potential, and multiunit activity (MUA) in the alert monkey visual cortex during presentation of natural movies. Using a general linear model, we show that in single trials, EEG power in the gamma band (30-100 Hz) and phase in delta band (2-4 Hz) are significant predictors of the MUA response. Specifically, we found that the MUA response was strongest only when increases in EEG gamma power occurred during the negative-going phase of the delta wave, thus revealing a frequency-band coupling mechanism that can be exploited to infer population spiking activity. This finding may open up a new dimension in the use and interpretation of EEG in normal and pathological conditions.},
web_url = {http://www.sciencedirect.com/science?_ob=PdfDownloadURL&_uoikey=B6WSS-4XJNCTW-J&_tockey=%23toc%237054%232009%23999359997%231546100%23FLA%23&_orig=search&_acct=C000003178&_version=1&_userid=29041&md5=06524a020e00f46c40979f4382aa},
state = {published},
DOI = {10.1016/j.neuron.2009.08.016},
author = {Whittingstall K{kevin}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 6046,
title = {Monkey drumming reveals common networks for perceiving vocal and nonvocal communication sounds},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
year = {2009},
month = {10},
volume = {106},
number = {42},
pages = {18010-18015},
abstract = {Salient sounds such as those created by drumming can serve as means of nonvocal acoustic communication in addition to vocal sounds. Despite the ubiquity of drumming across human cultures, its origins and the brain regions specialized in processing such signals remain unexplored. Here, we report that an important animal model for vocal communication, the macaque monkey, also displays drumming behavior, and we exploit this finding to show that vocal and nonvocal communication sounds are represented by overlapping networks in the brain's temporal lobe. Observing social macaque groups, we found that these animals use artificial objects to produce salient periodic sounds, similar to acoustic gestures. Behavioral tests confirmed that these drumming sounds attract the attention of listening monkeys similarly as conspecific vocalizations. Furthermore, in a preferential looking experiment, drumming sounds influenced the way monkeys viewed their conspecifics, suggesting that drumming serves as a multimodal signal of social dominance. Finally, by using high-resolution functional imaging we identified those brain regions preferentially activated by drumming sounds or by vocalizations and found that the representations of both these communication sounds overlap in caudal auditory cortex and the amygdala. The similar behavioral responses to drumming and vocal sounds, and their shared neural representation, suggest a common origin of primate vocal and nonvocal communication systems and support the notion of a gestural origin of speech and music.},
file_url = {/fileadmin/user_upload/files/publications/Remedios%20et%20al%202009%20Monkey%20Drumming%20(with%20supp%20info)_6046[0].pdf},
web_url = {http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2755465/pdf/pnas.0909756106.pdf},
state = {published},
DOI = {10.1073/pnas.0909756106},
author = {Remedios R{ryan}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ 5826,
title = {Optimizing the imaging of the monkey auditory cortex: sparse vs. continuous fMRI},
journal = {Magnetic Resonance Imaging},
year = {2009},
month = {10},
volume = {27},
number = {8},
pages = {1065-1073},
abstract = {The noninvasive imaging of the monkey auditory system with functional magnetic resonance imaging (fMRI) can bridge the gap between electrophysiological studies in monkeys and imaging studies in humans. Some of the recent imaging of monkey auditory cortical and subcortical structures relies on a technique of “sparse imaging,” which was developed in human studies to sidestep the negative influence of scanner noise by adding periods of silence in between volume acquisition. Among the various aspects that have gone into the ongoing optimization of fMRI of the monkey auditory cortex, replacing the more common continuous-imaging paradigm with sparse imaging seemed to us to make the most obvious difference in the amount of activity that we could reliably obtain from awake or anesthetized animals. Here, we directly compare the sparse- and continuous-imaging paradigms in anesthetized animals. We document a strikingly greater auditory response with sparse imaging, both quantitatively and qualitatively, which includes
a more expansive and robust tonotopic organization. There were instances where continuous imaging could better reveal organizational properties that sparse imaging missed, such as aspects of the hierarchical organization of auditory cortex. We consider the choice of imaging paradigm as a key component in optimizing the fMRI of the monkey auditory cortex.},
file_url = {/fileadmin/user_upload/files/publications/Petkov%20-%20Sparse%20vs%20Continuous%20MRI%20-%20MRI%20-%2009_5826[0].pdf},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T9D-4VT0H13-4-9&_cdi=5112&_user=29041&_orig=search&_coverDate=03%2F09%2F2009&_sk=999999999&view=c&wchp=dGLbVtb-zSkzS&md5=0d3cd98058c4dc88b34df154dd61d1b0&ie=},
state = {published},
DOI = {10.1016/j.mri.2009.01.018},
author = {Petkov CI{chrisp}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Augath M{mark}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 6147,
title = {Performance- and stimulus-dependent oscillations in monkey prefrontal cortex during short-term memory},
journal = {Frontiers in Integrative Neuroscience},
year = {2009},
month = {10},
volume = {3},
number = {25},
pages = {1-13},
abstract = {Short-term memory requires the coordination of sub-processes like encoding, retention, retrieval and comparison of stored material to subsequent input. Neuronal oscillations have an inherent time structure, can effectively coordinate synaptic integration of large neuron populations and could therefore organize and integrate distributed sub-processes in time and space. We observed field potential oscillations (14-95 Hz) in ventral prefrontal cortex of monkeys performing a visual memory task. Stimulus-selective and performance-dependent oscillations occurred simultaneously at 65-95 Hz and 14-50 Hz, the latter being phase-locked throughout memory maintenance. We propose that prefrontal oscillatory activity may be instrumental for the dynamical integration of local and global neuronal processes underlying short-term memory},
file_url = {/fileadmin/user_upload/files/publications/Pipa-Munk-2009-25_[0].pdf},
web_url = {http://www.frontiersin.org/integrativeneuroscience/paper/10.3389/neuro.07/025.2009/},
state = {published},
DOI = {10.3389/neuro.07.025.2009},
author = {Pipa G, St\"adtler ES, Rodriguez EF, Waltz JA, Muckli LF, Singer W, G\"obel R and Munk MHJ{munk}{Department Physiology of Cognitive Processes}}
}

@Article{ 5374,
title = {Where are the human speech and voice regions, and do other animals have anything like them?},
journal = {Neuroscientist},
year = {2009},
month = {10},
volume = {15},
number = {5},
pages = {419-429},
abstract = {Modern lesion and imaging work in humans has been clarifying which brain regions are involved in the processing of speech and language. Concurrently, some of this work has aimed to bridge the gap to the seemingly incompatible evidence for multiple brain-processing pathways that first accumulated in nonhuman primates. For instance, the idea of a posterior temporal-parietal “Wernicke’s” territory, which is thought to be instrumental for speech comprehension, conflicts with this region of the brain belonging to a spatial “where” pathway. At the same time a posterior speech-comprehension region ignores the anterior temporal lobe and its “what” pathway for evaluating the complex features of sensory input. Recent language models confirm that the posterior or dorsal stream has an important role in human communication, by a re-conceptualization of the “where” into a “how-to” pathway with a connection to the motor system for speech comprehension. Others have tried to directly implicate the “what” pathway
for speech comprehension, relying on the growing evidence in humans for anterior-temporal involvement in speech and voice processing. Coming full circle, we find that the recent imaging of vocalization and voice preferring regions in nonhuman primates allows us to make direct links to the human imaging data involving the anterior-temporal regions. We describe how comparisons of the structure and function of the vocal communication systems of human and nonhuman primates is clarifying the evolutionary relationships and the extent to which different species can model human brain function.},
web_url = {http://nro.sagepub.com/cgi/rapidpdf/1073858408326430v1},
state = {published},
DOI = {10.1177/1073858408326430},
author = {Petkov CI{chrisp}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Obleser J}
}

@Article{ 6119,
title = {Cell-Penetrating Peptides and Peptide Nucleic Acid-Coupled MRI Contrast Agents: Evaluation of Cellular Delivery and Target Binding},
journal = {Bioconjugate Chemistry},
year = {2009},
month = {9},
volume = {20},
number = {10},
pages = {1860-1868},
abstract = {Molecular imaging of cells and cellular processes can be achieved by tagging intracellular targets such as receptors, enzymes, or mRNA. Seeking to visualize the presence of
specific mRNAs by magnetic resonance (MR) imaging, we coupled peptide nucleic acids (PNA) with gadolinium-based MR contrast agents using cell-penetrating peptides for
intracellular delivery. Antisense to mRNA of DsRed2 protein was used as proof of principle. The conjugates were produced by continuous solid-phase synthesis followed by
chelation with gadolinium. Their cellular uptake was confirmed by fluorescence microscopy and spectroscopy as well as by MR imaging of labeled cells. The cell-penetrating
peptide D-Tat57&amp;amp;#8722;49 was selected over two other derivatives of HIV-1 Tat peptide, based on its superior intracellular delivery of the gadolinium-based contrast agents. Further
improved delivery of conjugates was achieved upon coupling
peptide nucleic acids (antisense to mRNA of DsRed2 protein and nonsense with no natural counterpart). Significant enhancement in MR contrast was obtained in cells labeled
with concentrations as low as 2.5 &amp;amp;#956;M of these agents. Specific binding of the targeting PNA containing conjugate to its complementary oligonucleotide sequence was proven
by in vitro cell-free assay. In contrast, a lack of specific enrichment was observed in transgenic cells containing the target due to nonspecific vesicular entrapment of contrast
agents. Preliminary biodistribution studies showed conjugate-related fluorescence in several organs, especially the liver and bladder, indicating high mobility of the agent in
spite of its high molecular weight. No conjugate related toxicity was observed. These results are encouraging, as they warrant further molecular optimization and consecutive
specificity studies in vivo of this new generation of contrast agents.},
file_url = {/fileadmin/user_upload/files/publications/MishraR2009_6119[0].pdf},
web_url = {http://pubs.acs.org/doi/pdf/10.1021/bc9000454},
state = {published},
DOI = {10.1021/bc9000454},
author = {Mishra R{ritu}{Department High-Field Magnetic Resonance}, Su W{wusu}{Department High-Field Magnetic Resonance}, Pohmann R{rolf}{Department High-Field Magnetic Resonance}, Pfeuffer J{josef}{Department Physiology of Cognitive Processes}, Sauer MG, Ugurbil K and Engelmann J{joern}{Department High-Field Magnetic Resonance}}
}

@Article{ 5734,
title = {In vivo 39K, 23Na and 1H MR imaging using a triple resonant RF coil setup},
journal = {Journal of Magntic Resonance},
year = {2009},
month = {9},
volume = {200},
number = {1},
pages = {134-136},
abstract = {The maintenance of a gradient of potassium and sodium ions across the cell membranes is essential for the physiological function of the mammal organism. The measurement of the spatial distribution of pathologically changing ion concentrations of 23Na and 39K  offers a very promising approach in clinical diagnostics. A lot of imaging and spectroscopy studies of 23Na exist already, as well as several spectroscopy studies and one post mortem imaging study for 39K. For MR imaging of both elements and the acquisition of anatomical proton images in the same experiment without moving the subject or the RF coil a triple-resonant RF coil setup for the rat head at 9.4T was developed. In vivo images of 39K and 23Na in the rat brain were acquired as well as anatomical proton images in the same scanning session.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WJX-4WBK7HR-3-7&_cdi=6890&_user=29041&_pii=S109078070900144X&_orig=search&_coverDate=09%2F30%2F2009&_sk=997999998&view=c&wchp=dGLbVlb-zSkzS&md5=8c2b3d5aeb20c},
state = {published},
DOI = {10.1016/j.jmr.2009.05.005},
author = {Augath M{mark}{Department Physiology of Cognitive Processes}, Heiler P, Kirsch S and Schad LR}
}

@Article{ 5895,
title = {Spatial Organization of Multisensory Responses in Temporal Association Cortex},
journal = {Journal of Neuroscience},
year = {2009},
month = {9},
volume = {29},
number = {38},
pages = {11924-11932},
abstract = {Neurons in sensory cortices are often topographically organized according to their response preferences. We here show that such an organization of response preferences also exists in multisensory association cortex. Using electrophysiological mappings we probed the modality preference to auditory and visual stimuli of neurons in the superior temporal association cortex of non-human primates. We found that neurons preferring the same modality (auditory or visual) often co-occur in close spatial proximity, or occur intermingled with bimodal neurons. Neurons preferring different modalities, in contrast, occur spatially separated. This organization at the scale of individual neurons leads to extended patches of same modality preference when analyzed at the scale of millimeters, revealing larger scale regions that preferentially respond to the same modality. In addition, we find that neurons exhibiting signs of multisensory interactions, such as super- or sub-additive response summation, also occur in spatial clus
ters. Together, these results reveal a spatial organization of modality preferences in a higher association cortex, and lend support to the notion that topographical organizations might serve as a general principle of integrating information within and across the sensory modalities.},
file_url = {/fileadmin/user_upload/files/publications/dahl_kayser2009_5895[0].pdf},
web_url = {http://www.jneurosci.org/cgi/reprint/29/38/11924},
state = {published},
DOI = {10.1523/JNEUROSCI.3437-09.2009},
author = {Dahl CD{dahl}{Department Human Perception, Cognition and Action}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ 6059,
title = {Extraction of Bistable-Percept-Related Features From Local Field Potential by Integration of Local Regression and Common Spatial Patterns},
journal = {IEEE Transactions on Biomedical Engineering},
year = {2009},
month = {8},
volume = {56},
number = {8},
pages = {2095-2103},
abstract = {Bistable perception arises when an ambiguous stimulus under continuous view is perceived as an alternation of two mutually exclusive states. Such a stimulus provides a unique opportunity for understanding the neural basis of visual perception because it dissociates the perception from the visual input. In this paper, we focus on extracting the percept-related features from the local field potential (LFP) in monkey visual cortex for decoding its bistable structure-from-motion (SFM) perception. Our proposed feature extraction approach consists of two stages. First, we estimate and remove from each LFP trial the nonpercept-related stimulus-evoked activity via a local regression method called the locally weighted scatterplot smoothing because of the dissociation between the perception and the stimulus in our experimental paradigm. Second, we use the common spatial patterns approach to design spatial filters based on the residue signals of multiple channels to extract the percept-related features. We exploit a support vector machine (SVM) classifier on the extracted features to decode the reported perception on a single-trial basis. We apply the proposed approach to the multichannel intracortical LFP data collected from the middle temporal (MT) visual cortex in a macaque monkey performing an SFM task. We demonstrate that our approach is effective in extracting the discriminative features of the percept-related activity from LFP and achieves excellent decoding performance. We also find that the enhanced gamma band synchronization and reduced alpha and beta band desynchronization may be the underpinnings of the percept-related activity.},
web_url = {http://ieeexplore.ieee.org/search/wrapper.jsp?arnumber=4812081},
state = {published},
DOI = {10.1109/TBME.2009.2018630},
author = {Wang Z, Maier A{amaier}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Liang H}
}

@Article{ 6056,
title = {Extraction of percept-related induced local field potential during spontaneously reversing perception},
journal = {Neural Networks},
year = {2009},
month = {8},
volume = {22},
number = {5-6},
pages = {720-727},
abstract = {The question of how perception arises from neuronal activity in the visual cortex is of fundamental importance in cognitive neuroscience. To address this question, we adopt a unique experimental paradigm in which bistable structure-from-motion (SFM) stimuli are employed to dissociate the visual input from perception while monitoring the cortical neural activity called local field potential (LFP). Consequently, the stimulus-evoked activity of LFP is not related to perception but the oscillatory induced activity of LFP may be percept-related. In this paper we focus on extracting the percept-related features of the induced activity from LFP in a monkey’s visual cortex for decoding its bistable structure-from-motion perception. We first estimate the stimulus-evoked activity via a wavelet-based method and remove it from the single-trial LFP. We then use the common spatial patterns (CSP) approach to design spatial filters to extract the percept-related features from the remaining induced activity. We exploit the linear discriminant analysis (LDA) classifier on the extracted features to decode the reported perception on a single-trial basis. We demonstrate that our approach has excellent performance in estimating the stimulus-evoked activity, outperforming the Wiener filter, least mean square (LMS), and a local regression method called the locally weighted scatterplot smoothing (LOWESS), and that our approach is effective in extracting the discriminative features of the percept-related induced activity from LFP, which leads to excellent decoding performance. We also discover that the enhanced gamma band synchronization and reduced alpha band desynchronization may be the underpinnings of the induced activity.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T08-4WNGW6V-2-7&_cdi=4856&_user=29041&_orig=search&_coverDate=08%2F31%2F2009&_sk=999779994&view=c&wchp=dGLbVtz-zSkWz&md5=54c9734c716fa4f7ea737ec60d2aaeb1&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.neunet.2009.06.037},
author = {Wang Z, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Liang H}
}

@Article{ 6309,
title = {Hippocampal sharp wave/ripples during sleep for consolidation of associative memory},
journal = {PLoS One},
year = {2009},
month = {8},
volume = {4},
number = {8},
pages = {1-9},
abstract = {The beneficial effect of sleep on memory has been well-established by extensive research on humans, but the neurophysiological mechanisms remain a matter of speculation. This study addresses the hypothesis that the fast oscillations known as ripples recorded in the CA1 region of the hippocampus during slow wave sleep (SWS) may provide a physiological substrate for long term memory consolidation. We trained rats in a spatial discrimination task to retrieve palatable reward in three fixed locations. Hippocampal local field potentials and cortical EEG were recorded for 2 h after each daily training session. There was an increase in ripple density during SWS after early training sessions, in both trained rats and in rats randomly rewarded for exploring the maze. In rats learning the place -reward association, there was a striking further significant increase in ripple density correlated with subsequent improvements in behavioral performance as the rat learned the spatial discrimination aspect of the task. The results corroborate others showing an experience-dependent increase in ripple activity and associated ensemble replay after exploratory activity, but in addition, for the first time, reveal a clear further increase in ripple activity related to associative learning based on spatial discrimination.},
file_url = {/fileadmin/user_upload/files/publications/2009_Ramadan%20et%20al_PLOS1%202009_[0].pdf},
web_url = {http://www.plosone.org/article/fetchObjectAttachment.action?uri=info%3Adoi%2F10.1371%2Fjournal.pone.0006697&representation=PDF},
state = {published},
DOI = {10.1371/journal.pone.0006697},
EPUB = {e6697},
author = {Ramadan W, Eschenko O{oeschenko}{Department Physiology of Cognitive Processes} and Sara SJ}
}

@Article{ 5963,
title = {Relaxometric, Thermodynamic and Kinetic Studies of Lanthanide(III)
Complexes of DO3A-Based Propylphosphonates},
journal = {European Journal of Inorganic Chemistry},
year = {2009},
month = {8},
volume = {2009},
number = {22},
pages = {3298-3306},
abstract = {Two DO3A-based ligands appended with the propylphosphonate side arm and their Ln3+ complexes were investigated. Proton relaxometric in vitro studies at 20 MHz and 60 MHz and 37 °C of the Gd3+ complex containing free acid exhibited relative changes of up to 56% in r1 relaxivity when the pH of the medium was changed from 4 to 7. This change is explained by the decrease in the number of coordinated water molecules from two to one. Temperature-dependent relaxivity and NMRD profiles of Gd3+ complexes showed a fast water exchange and a slightly increased rotational correlation time, which is characteristic of phosphonate-containing compounds. Thermodynamic and kinetic studies of the Gd3+ and Eu3+ complexes were performed by means of potentiometry and luminescence spectroscopy. The results indicate that the thermodynamic stability and kinetic inertness of these complexes are sufficient for their in vivo application.},
web_url = {http://www3.interscience.wiley.com/cgi-bin/fulltext/122464962/PDFSTART},
state = {published},
DOI = {DOI: 10.1002/ejic.200900149},
author = {Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, T{\'a}borsk{\'y} P, Lubal P, Laurent S, Elst LV, Mayer HA, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Angelovski G{goran}{Department Physiology of Cognitive Processes}}
}

@Article{ 6168,
title = {Vascular graph model to simulate the cerebral blood flow in realistic vascular networks},
journal = {Journal of Cerebral Blood Flow and Metabolism},
year = {2009},
month = {8},
volume = {29},
number = {8},
pages = {1429-1443},
abstract = {At its most fundamental level, cerebral blood flow (CBF) may be modeled as fluid flow driven through a network of resistors by pressure gradients. The composition of the blood as well as the cross-sectional area and length of a vessel are the major determinants of its resistance to flow. Here, we introduce a vascular graph modeling framework based on these principles that can compute blood pressure, flow and scalar transport in realistic vascular networks. By embedding the network in a computational grid representative of brain tissue, the interaction between the two compartments can be captured in a truly three-dimensional manner and may be applied, among others, to simulate oxygen extraction from the vessels. Moreover, we have devised an upscaling algorithm that significantly reduces the computational expense and eliminates the need for detailed knowledge on the topology of the capillary bed. The vascular graph framework has been applied to investigate the effect of local vascular dilation and occlusion on
the flow in the surrounding network.},
web_url = {http://www.nature.com/jcbfm/journal/v29/n8/pdf/jcbfm200958a.pdf},
state = {published},
DOI = {10.1038/jcbfm.2009.58},
author = {Reichold J{reichold}{Department Physiology of Cognitive Processes}, Stampanoni M, Keller AL{akeller}{Department Physiology of Cognitive Processes}, Buck A, Jenny P and Weber B{bweber}}
}

@Article{ 6057,
title = {A toolbox for the fast information analysis of multiple-site LFP, EEG and spike train recordings},
journal = {BMC Neuroscience},
year = {2009},
month = {7},
volume = {10},
number = {81},
pages = {1-24},
web_url = {http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=2723115&blobtype=pdf},
state = {published},
DOI = {10.1186/1471-2202-10-81},
author = {Magri C{cmagri}{Department Physiology of Cognitive Processes}, Whittingstall K{kevin}{Department Physiology of Cognitive Processes}, Singh V{vsingh}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Article{ 6096,
title = {Dissociable Perceptual Effects of Visual Adaptation},
journal = {PLoS ONE},
year = {2009},
month = {7},
volume = {4},
number = {7},
pages = {1-8},
abstract = {Neurons in the visual cortex are responsive to the presentation of oriented and curved line segments, which are thought to act as primitives for the visual processing of shapes and objects. Prolonged adaptation to such stimuli gives rise to two related perceptual effects: a slow change in the appearance of the adapting stimulus (perceptual drift), and the distortion of subsequently presented test stimuli (adaptational aftereffects). Here we used a psychophysical nulling technique to dissociate and quantify these two classical observations in order to examine their underlying mechanisms and their relationship to one another. In agreement with previous work, we found that during adaptation horizontal and vertical straight lines serve as attractors for perceived orientation and curvature. However, the rate of perceptual drift for different stimuli was not predictive of the corresponding aftereffect magnitudes, indicating that the two perceptual effects are governed by distinct neural processes. Finally, the rate
of perceptual drift for curved line segments did not depend on the spatial scale of the stimulus, suggesting that its mechanisms lie outside strictly retinotopic processing stages. These findings provide new evidence that the visual system relies on statistically salient intrinsic reference stimuli for the processing of visual patterns, and point to perceptual drift as an experimental window for studying the mechanisms of visual perception.},
web_url = {http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0006183},
state = {published},
DOI = {10.1371/journal.pone.0006183},
EPUB = {e6183},
author = {M\"uller K-M{kaim}{Department Human Perception, Cognition and Action}, Schillinger F{frieder}{Department Human Perception, Cognition and Action}, Do DH and Leopold DA{davidl}{Department Physiology of Cognitive Processes}}
}

@Article{ 6095,
title = {Color and shape interactions in the recognition of natural scenes by human and monkey observers},
journal = {Journal of Vision},
year = {2009},
month = {5},
volume = {9},
number = {5:14},
pages = {1-16},
abstract = {Trichromatic color vision is a fundamental aspect of the visual system shared by humans and non-human primates. In human observers, color has been shown to facilitate object identification. However, little is known about the role that color plays in higher level vision of non-human primates. Here, we addressed this question and studied the interaction between luminance- and color-based structural information for the recognition of natural scenes. We present psychophysical data showing that both monkey and human observers equally profited from color when recognizing natural scenes, and they were equally impaired when scenes were manipulated using colored noise. This effect was most prominent for degraded image conditions. By using a specific procedure for stimulus degradation, we found that the improvement as well as the impairment in visual memory performance is due to contribution of image color independent of luminance-based object information. Our results demonstrate that humans as well as non-human primates exploit their sensory ability of color vision to achieve higher performance in visual recognition tasks especially when shape features are degraded.},
web_url = {http://journalofvision.org/9/5/14/},
state = {published},
DOI = {10.1167/9.5.14},
author = {Liebe S{sliebe}{Department Physiology of Cognitive Processes}, Fischer E{efischer}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Article{ 6028,
title = {Directed interactions between auditory and superior temporal cortices and their role in multisensory integration},
journal = {Frontiers in Integrative Neuroscience},
year = {2009},
month = {5},
volume = {3},
number = {7},
pages = {1-11},
abstract = {Recent studies using functional imaging and electrophysiology demonstrate that processes related to sensory integration are not restricted to higher association cortices but already occur in early sensory cortices, such as primary auditory cortex. While anatomical studies suggest the superior temporal sulcus (STS) as likely source of visual input to auditory cortex, little evidence exists to support this notion at the functional level. Here we tested this hypothesis by simultaneously recording from sites in auditory cortex and STS in alert animals stimulated with dynamic naturalistic audio-visual scenes. Using Granger causality and directed transfer functions we first quantified causal interactions at the level of field potentials, and subsequently determined those frequency bands that show effective interactions, i.e. interactions that are relevant for influencing neuronal firing at the target site. We found that effective interactions from auditory cortex to STS prevail below 20Hz, while interactions from STS to auditory cortex prevail above 20Hz. In addition, we found that directed interactions from STS to auditory cortex make a significant contribution to multisensory influences in auditory cortex: Sites in auditory cortex showing multisensory enhancement received stronger feed-back from STS during audio-visual than during auditory stimulation, while sites with multisensory suppression received weaker feed-back. These findings suggest that beta frequencies might be important for inter-areal coupling in the temporal lobe and demonstrate that superior temporal regions indeed provide one major source of visual influences to auditory cortex.},
file_url = {/fileadmin/user_upload/files/publications/Kayser_FrontiersIntegrativeNeurosci_09_[0].pdf},
web_url = {http://www.frontiersin.org/integrativeneuroscience/paper/10.3389/neuro.07/007.2009/pdf/},
state = {published},
DOI = {doi:10.3389/neuro.07.007.2009},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5874,
title = {How not to study spontaneous activity},
journal = {NeuroImage},
year = {2009},
month = {5},
volume = {45},
number = {4},
pages = {1080-1089},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WNP-4VF56VB-1-7&_cdi=6968&_user=29041&_orig=search&_coverDate=05%2F01%2F2009&_sk=999549995&view=c&wchp=dGLbVlb-zSkWb&md5=89b06d7d2a46322519b4d916c334b3ba&ie=},
state = {published},
DOI = {10.1016/j.neuroimage.2009.01.010},
author = {Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Augath M{mark}{Department Physiology of Cognitive Processes}, Steffen T{theodor}, Werner J{joachim}{Department Physiology of Cognitive Processes} and Oeltermann A{axel}}
}

@Article{ 6058,
title = {Visually Driven Activation in Macaque Areas V2 and V3 without Input from the Primary Visual Cortex},
journal = {PLoS ONE},
year = {2009},
month = {5},
volume = {4},
number = {5},
pages = {1-14},
abstract = {Creating focal lesions in primary visual cortex (V1) provides an opportunity to study the role of extra-geniculo-striate pathways for activating extrastriate visual cortex. Previous studies have shown that more than 95% of neurons in macaque area V2 and V3 stop firing after reversibly cooling V1 [1], [2], [3]. However, no studies on long term recovery in areas V2, V3 following permanent V1 lesions have been reported in the macaque. Here we use macaque fMRI to study area V2, V3 activity patterns from 1 to 22 months after lesioning area V1. We find that visually driven BOLD responses persist inside the V1-lesion projection zones (LPZ) of areas V2 and V3, but are reduced in strength by ~70%, on average, compared to pre-lesion levels. Monitoring the LPZ activity over time starting one month following the V1 lesion did not reveal systematic changes in BOLD signal amplitude. Surprisingly, the retinotopic organization inside the LPZ of areas V2, V3 remained similar to that of the non-lesioned hemisphere, suggesting that LPZ activation in V2, V3 is not the result of input arising from nearby (non-lesioned) V1 cortex. Electrophysiology recordings of multi-unit activity corroborated the BOLD observations: visually driven multi-unit responses could be elicited inside the V2 LPZ, even when the visual stimulus was entirely contained within the scotoma induced by the V1 lesion. Restricting the stimulus to the intact visual hemi-field produced no significant BOLD modulation inside the V2, V3 LPZs. We conclude that the observed activity patterns are largely mediated by parallel, V1-bypassing, subcortical pathways that can activate areas V2 and V3 in the absence of V1 input. Such pathways may contribute to the behavioral phenomenon of blindsight.},
web_url = {http://www.plosone.org/article/fetchObjectAttachment.action;jsessionid=0A5232F6405DC5F1482FC1AB5827A3AD?uri=info%3Adoi%2F10.1371%2Fjournal.pone.0005527&representation=PDF},
state = {published},
DOI = {10.1371/journal.pone.0005527},
EPUB = {e5527},
author = {Schmid MC{mschmid}, Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Augath MA{mark}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Smirnakis SM{stelios}}
}

@Article{ 6143,
title = {Subsampling effects in neuronal avalanche distributions recorded in vivo},
journal = {BMC Neuroscience},
year = {2009},
month = {4},
volume = {2009},
number = {10:40},
pages = {1-20},
file_url = {/fileadmin/user_upload/files/publications/Priesemann-Wibral-2009-40_[0].pdf},
web_url = {http://www.biomedcentral.com/1471-2202/10/40},
state = {published},
DOI = {10.1186/1471-2202-10-40},
author = {Priesemann V, Munk MHJ{munk}{Department Physiology of Cognitive Processes} and Wibral M}
}

@Article{ 5764,
title = {Visual Perception: Converging Mechanisms of Attention, Binding and Segmentation?},
journal = {Current Biology},
year = {2009},
month = {4},
volume = {19},
number = {7},
pages = {R300-R302},
abstract = {Visual scenes are cluttered. Recent evidence suggests that areas as early as V1and V2 help making sense of the scene by segmenting them into distinct objects, separating foreground and background, and binding features.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6VRT-4W2F8TP-N-1&_cdi=6243&_user=29041&_orig=search&_coverDate=04%2F14%2F2009&_sk=999809992&view=c&wchp=dGLbVzz-zSkWb&md5=fd003d3f59a9a0eba0cc4f2f0cf67121&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.cub.2009.02.014},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Article{ 5707,
title = {Humans and Macaques Employ Similar Face-Processing Strategies},
journal = {Current Biology},
year = {2009},
month = {3},
volume = {19},
number = {6},
pages = {509-513},
abstract = {Primates developed the ability to recognize and individuate
their conspecifics by the face. Despite numerous electrophysiological
studies in monkeys [1–3], little is known about
the face-processing strategies that monkeys employ. In
contrast, face perception in humans has been the subject
of many studies [4–6] providing evidence for specific face
processing that evolves with perceptual expertise [7]. Importantly,
humans process faces holistically, here defined as
the processing of faces as wholes, rather than as collections
of independent features (part-based processing) [8]. The
question remains to what extent humans and monkeys share
these face-processing mechanisms. By using the same
experimental design and stimuli for both monkey and human
behavioral experiments, we show that face processing is
influenced by the species affiliation of the observed face
stimulus (human versus macaque face). Furthermore, stimulus
manipulations that selectively reduced holistic and
part-based information systematically altered eye-scanning
patterns for human and macaque observers similarly. These
results demonstrate the similar nature of face perception in
humans and monkeys and pin down effects of expert faceprocessing
versus novice face-processing strategies. These
findings therefore directly contribute to one of the central
discussions in the behavioral and neurosciences about
how faces are perceived in primates.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6VRT-4VPN17C-5-2&_cdi=6243&_user=29041&_orig=search&_coverDate=03%2F24%2F2009&_sk=999809993&view=c&wchp=dGLzVzz-zSkzk&md5=e6f38dd7719b33b8f0c6b73ddac9cc6f&ie=},
state = {published},
DOI = {10.1016/j.cub.2009.01.061},
author = {Dahl CD{dahl}{Department Human Perception, Cognition and Action}{Department Physiology of Cognitive Processes}, Wallraven C{walli}{Department Human Perception, Cognition and Action}, B\"ulthoff HH{hhb}{Department Human Perception, Cognition and Action} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5841,
title = {Metabolic and hemodynamic events after changes in neuronal activity: current hypotheses, theoretical predictions and in vivo NMR experimental findings.},
journal = {Journal of Cerebral Blood Flow and Metabolism},
year = {2009},
month = {3},
volume = {29},
number = {3},
pages = {441-463},
abstract = {Unraveling the energy metabolism and the hemodynamic outcomes of excitatory and inhibitory neuronal activity is critical not only for our basic understanding of overall brain function, but also for the understanding of many brain disorders. Methodologies of magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) are powerful tools for the noninvasive investigation of brain metabolism and physiology. However, the temporal and spatial resolution of in vivo MRS and MRI is not suitable to provide direct evidence for hypotheses that involve metabolic compartmentalization between different cell types, or to untangle the complex neuronal microcircuitry, which results in changes of electrical activity. This review aims at describing how the current models of brain metabolism, mainly built on the basis of in vitro evidence, relate to experimental findings recently obtained in vivo by 1H MRS, 13C MRS, and MRI. The hypotheses related to the role of different metabolic substrates, the metabolic neuron–glia interactions, along with the available theoretical predictions of the energy budget of neurotransmission will be discussed. In addition, the cellular and network mechanisms that characterize different types of increased and suppressed neuronal activity will be considered within the sensitivity-constraints of MRS and MRI.},
web_url = {http://www.nature.com/jcbfm/journal/v29/n3/pdf/jcbfm2008134a.pdf},
state = {published},
DOI = {10.1038/jcbfm.2008.134},
author = {Mangia S, Giove F, Tkac I, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Henry P-G, Olman CA, Maraviglia B, Salle FD and Ugurbil K}
}

@Article{ 5842,
title = {Cortical mechanisms of sensory learning and object recognition},
journal = {Philosophical Transactions of the Royal Society of London B},
year = {2009},
month = {2},
volume = {364},
number = {1515},
pages = {321-329},
abstract = {Learning about the world through our senses constrains our ability to recognise our surroundings. Experience shapes perception. What is the neural basis for object recognition and how are learning-induced changes in recognition manifested in neural populations? We consider first the location of neurons that appear to be critical for object recognition, before describing what is known about their function. Two complementary processes of object recognition are considered: discrimination among diagnostic object features and generalization across non-diagnostic features. Neural plasticity appears to underlie the development of discrimination and generalization for a given set of features, though tracking these changes directly over the course of learning has remained an elusive task.},
web_url = {http://rstb.royalsocietypublishing.org/content/364/1515/321.full.pdf+html},
state = {published},
DOI = {10.1098/rstb.2008.0271},
author = {Hoffman KL{kari}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5682,
title = {Functional MRI Evidence for LTP-Induced Neural Network Reorganization},
journal = {Current Biology},
year = {2009},
month = {2},
volume = {19},
number = {5},
pages = {398-403},
abstract = {The hippocampal formation is a region of the forebrain that is important for memory and spatial navigation [1] and [2]. On the basis of a vast amount of literature, the hippocampus is linked with long-term potentiation (LTP), the increased synaptic strength following repeated stimulation of the hippocampal neurons [3] and [4]. LTP is considered to be the experimental demonstration of Hebb‘s postulate on synaptic strength and learning [5], and it is the dominant model of an experience-dependent modification of brain circuits. Yet, despite the importance of this phenomenon for brain physiology and behavior, little is known about how experimentally measured regional synaptic modifications alter the activity of global, widespread networks. Here, we use simultaneous fMRI, microstimulation, and electrophysiology [6], [7] and [8] to unveil global changes in brain activity due to local hippocampal plasticity. Our findings offer the first evidence of an LTP-induced network reorganization that includes increased interhemispheric communication and recruitment of limbic and neocortical circuits after changes in synaptic strength within the hippocampus.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6VRT-4VN6FY0-2-2&_cdi=6243&_user=29041&_orig=search&_coverDate=03%2F10%2F2009&_sk=999809994&view=c&wchp=dGLbVzz-zSkWz&md5=d169ef23b3c11c387440f570325c554a&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.cub.2009.01.037},
author = {Canals S{canals}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Merkle H{hellmut} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5642,
title = {Spike-Phase Coding Boosts and Stabilizes Information Carried by Spatial and Temporal Spike Patterns},
journal = {Neuron},
year = {2009},
month = {2},
volume = {61},
number = {4},
pages = {597-608},
abstract = {Several codes have been proposed in order to explain how neurons encode sensory information. Here we tested the hypothesis that different codes might be employed concurrently and provide complementary stimulus-information. Quantifying the information encoded about natural sounds in the auditory cortex of alert animals, we found that temporal spike-train patterns and spatial populations were both highly informative. However, the relative phase of slow ongoing rhythms at which these (temporal or population) responses occurred provided much additional and complementary information. Such nested codes combining spike-train patterns with the phase of firing were not only most informative, but also most robust to sensory noise added to the stimulus. Our findings suggest that processing in sensory cortices could rely on the concurrent use of several codes that combine information across different spatio-temporal scales. In addition, they propose a role of slow cortical rhythms in stabilizing sensory representations b
y reducing effects of noise.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WSS-4VPDM89-F-2&_cdi=7054&_user=29041&_orig=search&_coverDate=02%2F26%2F2009&_sk=999389995&view=c&wchp=dGLbVzz-zSkzS&md5=1a3f96988080b3bcb7ab58a8b0a5e3e3&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.neuron.2009.01.008},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Montemurro MA, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Article{ 5627,
title = {The Coding of Color, Motion, and Their Conjunction in the Human Visual Cortex},
journal = {Current Biology},
year = {2009},
month = {2},
volume = {19},
number = {3},
pages = {177-183},
abstract = {Background. Colour and motion serve as the prime examples of segregated processing in the visual brain, giving rise to the question how colour-motion conjunctions are represented. This problem is also known as the ‘binding problem’.
Results. Human volunteers viewed visual displays containing coloured dots rotating around the centre. The dots could be red or green, and rotate clockwise or counter-clockwise, leading to four possible stimulus displays. Superimposed pairs of such stimuli provided two additional displays, each containing both colours and both directions of motion, but differing in their feature-conjunctions. We applied multivariate classifiers to voxel activation patterns obtained whilst subjects viewed such displays. Our analyses confirm the presence of directional motion information across visual cortex, and provide evidence of hue coding in all early visual areas except V5/MT+. Within each cortical area, information on colour and motion appeared to be coded in distinct sets of voxels. Furthermore, our results demonstrate the explicit representation of feature conjunctions in primary visual cortex and beyond.
Conclusions. The results show that conjunctions can be de-coded from spatial activation patterns already in V1, indicating an explicit coding of conjunctions at early stages of visual processing. Our findings raise the possibility that the solution of what has been taken as the prime example of the binding problem engages neural mechanisms as early as V1.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0960982209005442},
state = {published},
DOI = {10.1016/j.cub.2008.12.050},
author = {Seymour K{seymour}{Department Physiology of Cognitive Processes}, Clifford CWG{colinc}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Article{ 5640,
title = {An auditory region in the primate insular cortex responding preferentially to vocal communication sounds},
journal = {Journal of Neuroscience},
year = {2009},
month = {1},
volume = {29},
number = {4},
pages = {1034-1045},
abstract = {Human imaging studies implicate the insular cortex in processing complex sounds and vocal communication signals such as speech. In addition, lesions of the insula often manifest as deficits in sound or speech recognition (auditory agnosia) and speech production. While models of acoustic perception assign an important role to the insula, little is known about the underlying neuronal substrate. Studying a vocal primate we identified a predominantly auditory region in the caudal insula and therein discovered a neural representation of conspecific communication sounds. When probed with natural sounds insula neurons exhibited higher response selectivity than neurons in auditory cortex, and in contrast to these, responded preferentially to conspecific vocalizations. Importantly, insula neurons not only preferred conspecific vocalizations over a wide range of environmental sounds and other animal vocalizations, but also over acoustically manipulated versions of these, demonstrating that this preference for vocalizat
ions arises both from spectral and temporal features of the sounds. In addition, individual insula neurons responded highly selectively to only a few vocalizations and allowed the decoding of sound identity from single-trial responses. These findings characterize the caudal insula as a selectively responding auditory region, possibly part of a processing stream involved in the representation of communication sounds. Importantly, our results provide a neural counterpart for the human imaging and lesion findings and uncover a basis for a supposed role of the insula in processing vocal communication sounds such as speech.},
web_url = {http://www.jneurosci.org/cgi/reprint/29/4/1034},
state = {published},
DOI = {10.1523/JNEUROSCI.4089-08.2009},
author = {Remedios R{ryan}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ 5848,
title = {Relaxation-Based Feature Selection for Single-Trial Decoding of Bistable Perception},
journal = {IEEE Transactions on Biomedical Engineering},
year = {2009},
month = {1},
volume = {56},
number = {1},
pages = {101-110},
abstract = {Bistable perception refers to the phenomenon of spontaneously alternating percepts while viewing the same stimulus continuously. Bistable stimuli allow dissociation between stimuli and perception, and thus, provide a unique opportunity for understanding the neural basis of visual perception. In this paper, we focus on a relaxation (RELAX) based algorithm to select features from the multitaper spectral estimates of the multichannel intracortical local field potential (LFP), simultaneously collected from the middle temporal visual cortex of a macaque monkey, for decoding its bistable structure-from-motion (SFM) perception. We demonstrate that RELAX surpasses the conventional sequential forward selection (SFS) by offering the flexibility of modifying selected features. We propose a redundancy reduction preprocessing technique to significantly reduce the computational load for both SFS and RELAX. We exploit the support vector machines classifier based on the selected features for single-trial decoding the reported perception. Our results demonstrate the excellent performance of the RELAX feature selection algorithm. Furthermore, we find that the features in the gamma frequency band (30-100 Hz) of LFP are most relevant to bistable SFM perception. This finding is novel in awake monkey studies and suggests that gamma oscillations carry the most discriminative information for bistable perception of SFM stimuli.},
web_url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4595683&isnumber=4783498},
state = {published},
DOI = {10.1109/TBME.2008.2003260},
author = {Wang Z, Maier A{amaier}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Liang H}
}

@Article{ 5840,
title = {Visibility states modulate microsaccade rate and direction},
journal = {Vision Research},
year = {2009},
month = {1},
volume = {49},
number = {2},
pages = {228-236},
abstract = {We investigated how the perceptual visibility of a target influences the pattern of microsaccadic eye movements expressed during generalized flash suppression. We found that the microsaccade rate was highly dependent on the reported visibility of the target. In the visible trials, the microsaccade rate promptly rebounded to the pre-onset level, whereas on the invisible trials the rate remained low, reaching pre-onset levels hundreds of milliseconds later. In addition, the directional distributions of microsaccades were biased to the target positions in the visible condition. The present findings indicate that the microsaccade behavior is highly correlated with the perceptual state of target visibility, and suggest that the measured microsaccade rate and direction are reliable indicators of the perception.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T0W-4V11HPV-1-S&_cdi=4873&_user=29041&_orig=browse&_coverDate=01%2F31%2F2009&_sk=999509997&view=c&wchp=dGLbVzb-zSkWb&md5=925bf16a04dace4461d9c727d53780e9&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.visres.2008.10.015},
author = {Cui J, Wilke M{kwilke}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Leopold DA{davidl}{Department Physiology of Cognitive Processes} and Liang H}
}

@Inbook{ 5827,
title = {Cortical processing of vocal sounds in primates},
year = {2009},
month = {10},
pages = {135-147},
abstract = {The recent work on speech and vocal sound processing by the human brain finds itself at a crossroads with the studies in non-human primates on the neurobiological basis of vocal communication. Speech is a recent evolutionary adaptation, so direct animal homologs of the neural systems supporting speech perception are not expected. However, vocal expressions are richly informative for many social animals. Thus, the interest in how the human brain is processing the speaker‘s identity and affective aspects of the human voice, including the stimulus-bound aspects of speech, may be approached from an evolutionary perspective. From the other side, comparative biologists have started to close the gap between animal and human data by using the same noninvasive imaging techniques as those applied to the human brain, to study the brains of animals. Relying on the same techniques facilitates cross-species comparisons, and provides links to invasive studies of the brain processes at the neuronal level
. In this chapter, we consider how the brains of primates analyze the features in vocal sounds, focusing in particular on the correspondence between the auditory cortex processes in the brains of monkeys, apes and man.},
web_url = {http://www.elsevier.com/wps/find/bookdescription.cws_home/719106/description#toc},
editor = {Brudzynski, S. M.},
publisher = {Academic Press},
address = {London, UK},
series = {Handbook of Behavioral Neuroscience ; 19},
booktitle = {Handbook of mammalian vocalization: an integrative neuroscience approach},
state = {published},
ISBN = {978-0-12-374593-4},
DOI = {10.1016/B978-0-12-374593-4.00014-0},
author = {Petkov C{chrisp}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration} and Logothetis N{nikos}{Department Physiology of Cognitive Processes}}
}

@Inbook{ 5007,
title = {Brain Connectivity and Brain Size},
year = {2009},
month = {1},
volume = {2},
pages = {317-326},
abstract = {The mammalian brain varies in volume by five orders of magnitude. These size differences also affect the connectivity of the brain. In this article, we compare the cerebral and the cerebellar cortex in small and large brains. Both cortices show an almost proportionate increase in their surfaces with brain volume. However, there are fundamental differences in the structure between the two, such as the isotropic connectivity of the cerebral as opposed to the anisotropic connectivity of the cerebellar cortex and the self-connectedness on the cerebral as opposed to the feed-forward connectivity on the cerebellar cortex. These differences are also reflected in different scaling factors with brain size.},
web_url = {http://www.sciencedirect.com/science/referenceworks/9780080450469},
editor = {Squire, L. R., T. Albright, F. Bloom, F. Gage, N. Spitzer},
publisher = {Academic Elsevier},
address = {London, UK},
booktitle = {Encyclopedia of Neuroscience},
state = {published},
DOI = {10.1016/B978-008045046-9.00937-2},
author = {Sch\"uz A{schuez}{Department Physiology of Cognitive Processes} and Sultan F}
}

@Inbook{ 7094,
title = {Neural Networks and Architectures},
year = {2009},
volume = {14},
pages = {2588-2592},
web_url = {http://www.springerlink.com/content/j804632515769870/fulltext.html},
editor = {Binder, M.D. , N. Hirokawa, U. Windhorst},
publisher = {Springer},
address = {Berlin, Germany},
booktitle = {Encyclopedia of Neuroscience},
state = {published},
ISBN = {978-3-540-29678-2},
DOI = {10.1007/978-3-540-29678-2_3794},
author = {Aihara K, Okada M, Adachi M and Watanabe M{watanabe}{Department Physiology of Cognitive Processes}}
}

@Poster{ NevesEEBL2009,
title = {Anterograde analysis of noradrenergic projections in the rat forebrain using classical and manganese-enhanced MRI (MEMRI) tract-tracing},
year = {2009},
month = {11},
volume = {10},
number = {10},
pages = {29},
abstract = {We examined anterograde labeling of noradrenergic terminals originating from the neurons of brain stem neuromodulatory nucleus Locus Coeruleus (LC), a major course of noradrenaline in the rat forebrain, by means of simultaneous iontophoretic injection of paramagnetic
(Mn2 +) and classical (fluorescent dextran) tracers in the LC. Both MEMRI and fluorescent microscopy revealed anterograde labeling in major terminal fields of LC neurons
(Swanson and Hartman, 1975; Ungerstedt, 1971) 24 h and 5 d after injection, respectively. Predominantly ipsilateral labeling of thalamic nuclei, primary sensory cortices, medial prefrontal cortex, and olfactory bulbs reflected previously demonstrated monosynaptic projections of
the LC neurons in multiple target brain regions. The labeling patterns of both paramagnetic and classical tracers were strikingly similar. Importantly, iontophoretic injection of Mn2+ did not produce neurotoxic effects as there were no signs of neuronal death or glial inflammatory
reaction at the injection site 5 days after injection. The reported results further validate MEMRI tract-tracing technique allowing visualization a highly distributed and distal efferent projections arising from the brain stem nucleus. Thus, MEMRI may be used for mapping convergent target brain regions of different neuromodulatory systems in the same animal and their functional reorganization in longitudinal studies.},
web_url = {http://www.neuroschool-tuebingen-nena.de/},
event_name = {10th Conference of Junior Neuroscientists of Tübingen (NeNa 2009)},
event_place = {Ellwangen, Germany},
state = {published},
author = {Neves RM{ricardo}{Department Physiology of Cognitive Processes}, Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}, Evrard H{evrard}{Department Physiology of Cognitive Processes}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ KapoorWPKL2009,
title = {Comparing inter-ocular switch and classical binocular rivalry in the human brain using EEG},
year = {2009},
month = {11},
volume = {10},
number = {3},
pages = {22},
abstract = {When disparate visual stimuli are presented to corresponding retinal locations, perception fluctuates between the presented stimuli. This phenomenon, called binocular rivalry, is an exquisite tool to dissociate sensory stimulation from visual perception. It has therefore been extensively used for studying the neural correlates of visual awareness. Initial theories have
tried to explain binocular rivalry by hypothesizing the resolution of competition in V1 through inhibitory interactions between monocular neurons. However, inter-ocular switch rivalry, a paradigm where the rivaling stimuli are rapidly exchanged between the eyes also results in stable percepts that span several swaps of the visual stimuli. This has demonstrated that competition also involves higher-level stimulus representations, and not just eye based sensory information. In this study, we compared the electrophysiological correlates underlying
stable visual percepts during inter-ocular switch and binocular rivalry. Delineating the differences
and similarities between the two paradigms of rivalry will provide us with valuable information on the nature of competition during incongruent visual stimulation. We recorded EEGs while human subjects experienced inter-ocular switch and classical binocular rivalry elicited with dichoptic presentation of orthogonally oriented sinusoidal gratings. The subjects reported their percepts via button presses. We extracted and analyzed trials, where subjects
reported at least one second long stable percepts. During this time window, we assessed the normalized spectrogram to visualize mean event-related changes in spectral power across a broad frequency range (1 - 45 Hz). We observed a strong and sustained increase in spectral power between 12 - 30 Hz across the two conditions approximately 300 ms following the reported perceptual switch. Low Resolution Brain Electromagnetic Tomography (LORETA) was used to localize the cortical sources of the observed changes. The maps of the localized cortical sources of this increase in the spectral power during inter-ocular switch and binocular
rivalry were remarkably similar and showed no significant differences. We therefore propose that both types of rivalry have similar EEG correlates in the 12 - 30 Hz frequency band during a stable visual percept.
22},
web_url = {http://www.neuroschool-tuebingen-nena.de/},
event_name = {10th Conference of Junior Neuroscientists of Tübingen (NeNa 2009)},
event_place = {Ellwangen, Germany},
state = {published},
author = {Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Whittingstall K{kevin}{Department Physiology of Cognitive Processes}, Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Keliris G{george}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ PietrajtisSLE2009,
title = {Dopaminergic and noradrenergic modulation of the rat prefrontal cortex: in vivo electrophysiological study},
year = {2009},
month = {11},
volume = {10},
number = {8},
pages = {27},
abstract = {Several investigations suggest that dopaminergic and noradrenergic neuromodulatory systems may simultaneously modulate their common targets. Moreover, the midbrain ventral tegmental area (VTA) and brain stem nucleus locus coeruleus (LC), the major sources of forebrain dopamine and noradrenaline, respectively, are reciprocally connected. The latter suggests that these two systems may be functionally interdependent. The aim of our experiments
was to characterize spontaneous and evoked activity of these two neuromodulatory centers in parallel with monitoring neural activity in the medial prefrontal cortex (mPFC), their common projection structure. All experiments were performed in rats under urethane anesthesia. We recorded unit activity and local field potentials simultaneously from VTA, LC and mPFC. A number of electrophysiological and pharmacological criteria were used to distinguish VTA and LC neurons. Evoked activity was induced by a mild electrical stimulation of the hind paw. We also applied intrabrain microstimulation technique for VTA or LC regions and tested neural responses in mPFC. First, we observed a burst-like activation of LC neurons in response to hind paw stimulation with the response latency 20 ms. Brief LC activation followed by a prolonged (300 ms) inhibition. VTA neurons showed inhibitory response to the hind paw stimulation, but only if stimulation parameters were substantially stronger compared to those that activated LC (e. g. trains of pulses at 50 Hz for 100 ms).
The preliminary results have not yet revealed any strong temporal relationships between spontaneous or evoked activity between VTA and LC. VTA firing may precede or follow the mPFC firing. Such response pattern may be related to the fact that VTA is a heterogeneous
brain region containing dopaminergic, non-dopaminergic and GABA-ergic neurons. We plan to apply juxtacellular labeling technique in combination with immunohistochemical staining
procedures in order to more reliably identify the neuronal types in VTA.},
web_url = {http://www.neuroschool-tuebingen-nena.de/},
event_name = {10th Conference of Junior Neuroscientists of Tübingen (NeNa 2009)},
event_place = {Ellwangen, Germany},
state = {published},
author = {Pietrajtis K{kpietrajtis}{Department Physiology of Cognitive Processes}, Sara SJ, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}}
}

@Poster{ MusallLW2009,
title = {Frequency-band coupling in surface EEG reflects spiking activity in monkey V1 during passive fixation},
year = {2009},
month = {11},
volume = {10},
number = {12},
pages = {31},
abstract = {Although EEG is one of the most widely used tools to study brain activity in humans, its neurophysiological constituents are not well understood. We recently showed that during the presentation of movie stimuli, the multi unit activity (MUA) in V1 could be accurately modeled
by using the EEG modulations in low frequency (2 - 4 Hz) phase and high frequency (30 Hz) power. However, whether this relationship also holds for situations without direct
visual stimulation remains unanswered. Therefore, we present data from simultaneous recordings of surface EEG and MUA in area V1 of one behaving monkey during a simple fixation task (trials consisted of a 9 second fixation period). In each trial, we first filtered the data
into the delta (2 - 4 Hz) and gamma (30 Hz) band, and found that changes in MUA were positively correlated to gamma power (R=0.12±0.03), and significantly tuned to the phase
of the delta oscillation (rayliegh test, p0.001). Furthermore, we found that MUA responses were greatest when an increase in gamma power coincided with the negative-going (0.8 ) phase of the delta oscillation, suggesting that the strength of MUA in V1 is directly related to the precise interaction of low frequency phase and high frequency power (frequency-band coupling or FBC). These results resemble our earlier findings during the presentation of movie stimuli, and suggest that the relationship between FBC and MUA holds true in both stimulus
and stimulus-free conditions.},
web_url = {http://www.neuroschool-tuebingen-nena.de/},
event_name = {10th Conference of Junior Neuroscientists of Tübingen (NeNa 2009)},
event_place = {Ellwangen, Germany},
state = {published},
author = {Musall S{unone}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Whittingstall K{kevin}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6162,
title = {Attention to motion: Differential cortical modulation to forward and planar visual flow},
year = {2009},
month = {10},
volume = {39},
number = {558.21},
abstract = {Self- and object-motion processing greatly relies on visual cues. There are at least two entirely independent kinds of self-induced visual motion that combine to optic flow in the visual field: expansion flow, such as that induced by forward motion in depth, or planar motion, such as induced by translational self-motion or by pursuit eye movements across a visual scene. In real life, both signals may occur in combination, yet, only one of the cues may be of behavioral relevance, thus requiring to be selectively attended to. In this fMRI study we attempt to address the question whether differential neural substrates get modulated by selective attention to either one of these motion cues. We created a stimulus combining an expansion flow pattern with translational motion on the same set of dots. In a feature-based detection task, subjects selectively attended either to the expansion or to the translation component of the stimulus and reported changes in the speed of the attended motion component. In control conditions that used the same stimuli subjects attended to color hue changes of the fixation cross, or passively fixated the stimulus without any attentional demand. In each of the three attention conditions, the attentional load was kept constant across conditions by a continuously updating staircase procedure.
We found that attention to expansion modulated the separately localized areas MT/V5, MST, and V3A significantly more than attention to translation. This is in line with stimulus-driven studies that showed a preference to expansion/contraction stimuli in these areas (Smith et al., 2006). In contrast, V7 and the cingulate sulcus visual area (CSv) differed from all other regions, in that they did not show any selective modulation by attention to expansion flow. Most interestingly, we found motion selective modulation in the foveal confluence of V1, despite a physical match between stimulus conditions. This might be due to differential attentional enhancement within V1, or by differential feedback from higher regions such as MT/V5, MST or V3A. Our results therefore show a differential attentional modulation within the motion-processing pathway, depending on the type of motion-component that is attended to within the same flow stimulus.
Smith AT, Wall MB, Williams AL, Singh KD (2006) Sensitivity to optic flow in human cortical areas MT and MST.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=3b1b2e24-3671-4e3d-9051-5dfbb3c15f6c&cKey=81bf6c91-1c74-4f55-870b-c12dbcb94af7},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Fischer E{efischer}{Department Physiology of Cognitive Processes}, B\"ulthoff HH{hhb}{Department Human Perception, Cognition and Action}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6289,
title = {Capillary unisotropy in the rat and monkey cerebral cortex},
year = {2009},
month = {10},
volume = {39},
number = {672.13},
abstract = {Although at the basis of cerebral blood flow (CBF) control and neurovascular coupling, very little is known about the exact topology of the cerebrovascular network. Furthermore, a better understanding of the cerebral vascular network is essential for numerical simulations of CBF (Reichold et al., 2009, J Cereb Blood Flow Metab and additional poster at this symposium).
Arterioles that branch off the pial vessels plunge into the cerebral cortex where they form collaterals at various cortical depths, which further divide unto capillary level. The capillary bed is the major site of exchange where nutrients and oxygen are delivered to the parenchyma and metabolites and heat are removed. The capillaries rejoin to form the draining veins which penetrate the cortex towards its surface. It is generally accepted that the large cortical vessels run orthogonally to cortical surface, whereas the capillaries are oriented isotropically.
Deeply anaesthetized rats and macaque monkeys were transcardially perfused with heparinized phosphate buffered saline followed by paraformaldehyde. Then, a dispersed suspension of barium sulfate was injected. After removal of the brain, cylindrical samples of from the somatosensory and visual cortex were punched out and embedded in EPON. The samples were then imaged using monochromatic X-rays with a beam energy set to 20 keV to maximize absorption contrast and to provide sufficient photon flux to penetrate the large sample. The optical magnification was 20x, resulting in isotropic voxels of 700 nm for the reconstructed images. The tomographic images were used to reconstruct and analyse the vascular network.
We show that the capillaries are not, as previously assumed, oriented isotropically but are rather designed for mass transport parallel to the cortical surface. This property is not readily apparent due to the tortuosity of the vessels. If, however, one replaces the individual capillaries by straight cylindrical segments that connect points of bifurcation, so as to look at the effective directionality of blood flow, the overwhelming dominance of horizontally oriented segments (with respect to the cortical surface) is striking. Within the cortical gray matter, this dominance increases with the cortical depth. The fraction of capillary segments with angles between 0 and 45 degrees to the cortical surface can reach values of more than 80%. As both feeding arteries and draining veins sport higher numbers of side branches at larger cortical depths, the capillary orientation specificity thus is proportional to the frequency of non-capillary vessels that are orthogonal to the cortical surface and accomplish the vertical mass transport.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=e5c57598-6c32-4a6f-ad00-6d5b5fa2f8c4&cKey=63192534-c1c3-4fdc-b1c7-44469034c9ea},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Reichold J{reichold}{Department Physiology of Cognitive Processes}, Stampanoni M, Keller AL{akeller}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Jenny P and Weber S}
}

@Poster{ 6283,
title = {Category selectivity in features of the local field potentials and single cell activity simultaneously recorded from the inferior temporal cortex of the macaque monkey},
year = {2009},
month = {10},
volume = {39},
number = {262.6},
abstract = {Although there is evidence suggesting that the inferior temporal (IT) cortex plays an important role in face processing and categorization, the exact neural mechanisms underlying these cognitive functions remain unknown. Here we address this issue by simultaneously recording the local field potentials (LFP) and single cells activity at 202 sites of the inferior temporal cortex (IT) of two macaques, while they passively fixated at pictures of monkey faces, human faces and objects. Our first goal was to investigate which features of the LFP, in frequency and time domains, were able to represent natural categories. For that, we calculated a selectivity index at two granularity levels: face vs. object (‘coarse’ selectivity) and monkey vs. human faces (‘fine’ selectivity). Our second goal was to study correlations between the selectivity of the LFP features and the selectivity of single cells recorded at the same sites. The data was first pre-processed as follows: for the LFPs we computed on each recording site: a) Visual-evoked-potentials (VEPs) and b) Single-trial-based instantaneous power and phase for different frequency bands. For the single cells we calculated i) Mean firing rate across trials and ii) Mutual information between stimulus classes and their associated responses (on each single-trial). Regarding selectivity of the VEPs, specifically the P100 deflection, we found that its onset latency occurred earlier for faces than for objects (p<0.01) and for monkey than for human faces (p<0.05). In contrast, the P100 amplitude did not systematically differentiate between these categories. In the frequency domain, we found that the degree of phase-locking (across trials in single electrodes) of the theta-band (4-8 Hz) around the P100 (80 ms to 120 ms after stimulus presentation) discriminated between faces/objects (p<0.01) and humans/monkeys (p<0.01). Considering correlations between selectivity of the LFP features and single cells, we found that ‘coarse’ (faces vs. objects) selectivity of the VEPs, particularly when using the amplitude of the N170 deflection, and also selectivity of the phase-locking of the gamma-band (low gamma: 28-48 Hz) around P100, significantly correlated (p<0.05) with the information about faces and objects of the single cells at those locations. More effects on correlations between LFP features and single cell activity will be discussed during the presentation. By showing that time related features of neural signals can better discriminate “coarse” and “fine” differences, and describing relations between these features, we provide novel insights into the neural mechanisms of object and face recognition.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=b7a30480-b3fd-481b-bc5c-1105adf9ca4e&cKey=88ead301-9a70-40b9-b39b-4030aba9566f},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Sigala Alanis GR{sigala}{Department Physiology of Cognitive Processes}, Veit J{jveit}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ 6286,
title = {Comparing inter-ocular switch and classical binocular rivalry in the human brain using eeg},
year = {2009},
month = {10},
volume = {39},
number = {380.11},
abstract = {When disparate visual stimuli are presented to corresponding retinal locations in the two eyes, perception fluctuates between the presented stimuli. This phenomenon, called binocular rivalry, is an exquisite tool to dissociate sensory stimulation from visual perception. It has therefore been extensively used for studying the neural correlates of visual awareness. Initial theories have tried to explain binocular rivalry by hypothesizing the resolution of competition in V1 through inhibitory interactions between monocular neurons. However, inter-ocular switch rivalry, a paradigm where the rivaling stimuli are rapidly exchanged between the eyes also results in stable percepts that span several swaps of the visual stimuli. This has demonstrated that competition also involves higher level stimulus representations, and not just eye based sensory information. In this study, we compared the electrophysiological correlates underlying stable visual percepts during inter-ocular switch and classical binocular rivalry. Delineating the differences and similarities between the two paradigms of rivalry will provide us with valuable information on the nature of competition during incongruent visual stimulation. We recorded EEGs while human subjects experienced inter-ocular switch and classical binocular rivalry elicited with dichoptic presentation of orthogonally oriented sinusoidal gratings. The subjects reported their percepts via button presses. We extracted and analyzed trials, where subjects reported at least one second long stable percepts. During this time window, we assessed the normalized spectrogram to visualize mean event-related changes in spectral power across a broad frequency range (1-45 Hz). We observed a strong and sustained increase in spectral power between 12-30 Hz across the two conditions approximately 300 ms following the reported perceptual switch. Low Resolution Brain Electromagnetic Tomography (LORETA) was used to localize the cortical sources of the observed changes. The maps of the localized cortical sources of this increase in the spectral power during inter-ocular switch and binocular rivalry were remarkably similar and showed no significant differences. We therefore propose that both types of rivalry have similar EEG correlates in the 12-30 Hz frequency band during a stable visual percept.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=f5dec3fb-2bb6-482d-8553-db756136f1a1&cKey=a119d583-ca30-4a52-801f-b1aed085e303},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Whittingstall K{kevin}{Department Physiology of Cognitive Processes}, Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6281,
title = {Dynamical changes in functional circuitry of the macaque prefrontal cortex mediating a perceptual switch},
year = {2009},
month = {10},
volume = {39},
number = {622.17},
abstract = {Binocular rivalry (BR) has been successfully combined with extracellular electrophysiological recordings in awake, behaving macaques to study the cortical mechanisms of visual conscious experience. The contribution of different cortical areas to visual awareness is commonly determined by reporting the percentage of neurons modulated, in each area, in accordance with the percept. However, in order to obtain a detailed understanding of the cortical mechanisms mediating subjective visual perception it is likely that valuable insights could be gained by studying the neuronal interactions within pools of neurons sharing similar stimulus preference. One of the most commonly studied forms of neuronal interaction is noise (or spike count) correlations i.e the correlation in the variability around the mean of trial by trial spike counts between pairs of simultaneously recorded neurons. In this study we used binocular flash suppression (BFS), a highly controlled variant of BR, to explore the neuronal correlates of visual awareness in the inferior prefrontal convexity (icPFC) of the macaque brain while simultaneously recording pairs of neurons preferring the same visual stimulus. We report that the perception of a stimulus under rivalrous conditions is accompanied by a drastic decrease in noise correlations between neurons sharing a similar preference to this stimulus compared to noise correlations when the same stimulus is perceived without competition. We propose that this decorrelation of neuronal discharges during visual competition is optimal for rivalrous perception since it renders the dominant neural population representing the perceived stimulus more sensitive to it by increasing the signal to noise ratio conveyed by signal averaging. This is in agreement with local correlation models that predict enhanced information coding as a result of decorrelated noise between neurons with similar tuning functions. Similar studies in other visual cortical areas during rivalrous visual stimulation could show whether reduction of correlated noise is observed throughout the ventral visual stream or it is a unique property of the ventral prefrontal cortex.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=abbf38a3-9e54-4ec7-a483-d333079a2cc8&cKey=97c91e04-79b8-454d-817e-7ac52c33e4e3},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Komlos M{marcell}, Kapoor V{vishal}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6287,
title = {EEG source imaging during continuous viewing of natural movies},
year = {2009},
month = {10},
volume = {39},
number = {651.13},
abstract = {Electroencephalography (EEG) is a non-invasive neuroimaging tool which can be used to measure brain activity with excellent temporal resolution. By solving the so-called ‘inverse problem’, one can not only study the time-course of activation during a particular task, but also identify the location of the underlying neural sources in the brain. Usually, these methods are applied to averaged data obtained from EEG recordings during which volunteers perform a given, usually brief (0.1-5s) task over many dozens repetitions. This averaging across many brief trials results in clearer responses, as artifactual or randomly occurring events (noise, eye blinks, eye wanderings, etc) will be reduced. Here, we take a radically new approach, and ask whether one can obtain reliable source localization associated to a particular stimulus feature (such as visual contrast) when using complex natural stimuli presented over long periods of time. We made EEG recordings (64 channels) in 7 subjects who passively watched 2 minute long segments from different commercially available movies (the segments were repeated 20 times). We then developed a method based on independent component analysis (ICA) to reject EEG artifacts due to blinks, subject movement, etc. Source localization of this artifact-free data was calculated at each time point of the movie using low resolution electromagnetic tomography (LORETA). We then calculated the correlation coefficient between variations in the EEG source strength in over 6000 voxels within the brain with variations in movie contrast. As expected, we found that visual contrast in the movie mapped specifically to voxels within area V1, thus showing that a feature that varies continuously in its strength can be reliably mapped onto the cortical region involved in its processing. These findings open a new approach to mapping brain function with a high temporal resolution and allow the localization of a multitude of brain areas based on a single experiment using uncontrolled, natural stimuli.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=b20c565a-8249-480b-8c35-daf17e2d8523&cKey=e1de2d8a-b4aa-4d62-adc3-a4d2b575c82a},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Whittingstall KS{kevin}{Department Physiology of Cognitive Processes}, Bartels A{abartels}{Department Physiology of Cognitive Processes}, Kwon S, Singh V{vsingh}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6282,
title = {Frequency-band coupling in surface EEG reflects spiking activity in monkey V1 during passive fixation},
year = {2009},
month = {10},
volume = {39},
number = {166.11},
abstract = {Although EEG is one of the most widely used tools to study brain activity in humans, its neurophysiological constituents are not well understood. We recently showed that during the presentation of movie stimuli, the multi unit activity (MUA) in V1 could be accurately modeled by using the EEG modulations in low frequency (2-4 Hz) phase and high frequency (>30 Hz) power. However, whether this relationship also holds for situations without direct visual stimulation remains unanswered. Therefore, we present data from simultaneous recordings of surface EEG and MUA in area V1 of one behaving monkey during a simple fixation task (trials consisted of a 9 second fixation period). In each trial, we first filtered the data into the delta (2-4Hz) and gamma (>30Hz) band, and found that changes in MUA were positively correlated to gamma power (R=0.12±0.03), and significantly tuned to the phase of the delta oscillation (rayliegh test, p<<0.001). Furthermore, we found that MUA responses were greatest when an increase in gamma power coincided with the negative-going (~ 0.8π) phase of the delta oscillation, suggesting that the strength of MUA in V1 is directly related to the precise interaction of low frequency phase and high frequency power (frequency-band coupling or FBC). These results resemble our earlier findings during the presentation of movie stimuli, and suggest that the relationship between FBC and MUA holds true in both stimulus and stimulus-free conditions.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=420e16ba-b7d1-448e-a3c2-ccfa75c2fdf5&cKey=d83bcae8-9514-41bb-ad59-89e756b654d8},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Musall S{unone}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Whittingstall KS{kevin}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6178,
title = {Frontoparietal activity with minimal decision and control in the awake macaque at 7T},
year = {2009},
month = {10},
volume = {39},
number = {677.16},
abstract = {In the primate brain a frontoparietal network is involved in many aspects of cognitive control, e.g. during shifts of attention and switches of abstract rules. However, the frontoparietal network in the human brain is also active during simple update of attended information, when task-related decision making is minimal (1) or during the execution of voluntary eye movements (2). The goal of the present study was to identify the network of areas activated by a short series of visual stimuli (meaningless fractal images) while the animals were awake and maintained fixation, in order to compare with the activations elicited in the human brain and to inform and direct future single unit recordings. We obtained activation maps at 7T using BOLD fMRI in three alert macaque monkeys (Macaca mulatta). Functional images were realigned and co-registered with the high-resolution MRI images used in the Saleem and Logothetis atlas (3) to facilitate the identification of the anatomical structures. Areas that were reliably activated in all three animals included areas 8 and F5 around the arcuate sulcus (AS), and the lateral intraparietal area (LIP), along with early and higher areas of the visual system. As in the human, extensive frontoparietal activity was seen despite maintained fixation, and without active behavioural decisions.
Additionally, we present preliminary psychophysical and BOLD fMRI results from a second study. In this experiment, we trained one animal to perform a colour discrimination task by making a saccade to the left (for green) or right (for red) of the screen, and then introduced conditions of increased task difficulty.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=e599a515-6cac-432b-bd54-1c49698414ac&cKey=ab501a56-65bf-4152-a13d-9d50c2bd66d7},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Stoewer S{stoewer}{Department Physiology of Cognitive Processes}, Ku S-PP{shihpi}{Department Physiology of Cognitive Processes}, Goense J{jozien}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Duncan J and Sigala N{natasha}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6113,
title = {Graded cooling of the skin activates the insular cortex in the anesthetized macaque monkey},
year = {2009},
month = {10},
volume = {39},
number = {854.8},
abstract = {Neuroanatomical and functional evidence indicates that pain and temperature are represented with numerous other interoceptive sensory inputs in a phylogenetically novel spinothalamocortical pathway in primates (for review, see Craig, TINS 2003 26:303-307). Prior tract-tracing studies in the monkey demonstrated that nociceptive and thermoreceptive spinothalamic tract neurons in spinal lamina I primarily project to the posterior part of the ventromedial nucleus of the thalamus (VMpo; a nucleus specific to primates) and that nociceptive and thermoreceptive thalamocortical tract neurons in VMpo project to the dorsal posterior insular cortex. Electrophysiological recordings in spinal lamina I and VMpo in the anesthetized monkey revealed precise encoding of the grading of thermal and pain stimuli. Functional imaging in humans and EEG in monkeys indicated that the dorsal posterior insula is strongly activated by graded cooling of the skin. In the present study, we examined the activation of the insular cortex using high-resolution functional magnetic resonance imaging (4.7T) with thermal stimulation of the skin in two anesthetized cynomolgus monkeys. A graded cooling of the palmar surface of the foot from a baseline temperature of 35°C to a target temperature of 15°C (0.5°C/sec) followed by a re-warming to baseline (0.5°C/sec) produced highly significant (p < 0.001) BOLD signal exclusively in the dorsal mid-posterior portion of the contralateral insular cortex. No or poorly significant (p < 0.05) BOLD signal occurred in primary and secondary somatosensory cortices. These results support prior evidence that the insula in primates encodes ongoing interoceptive activity necessary to maintain homeostatic balance (e.g. thermoregulation). Neuroanatomical tract-tracers were injected in the insular regions displaying significant BOLD signal; mapping of anterograde and retrograde labeling from these injections will be presented.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=900967bd-51c4-4851-bf1c-9ac4ab8672ed&cKey=50872dae-3636-42e4-a7d3-d49edcf1e79e},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Evrard HC{evrard}{Department Physiology of Cognitive Processes}, Augath M{mark}{Department Physiology of Cognitive Processes}, Baumg\"artner U, Craig AD, Treede RD and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6288,
title = {Long range coupling between V4 and PF in theta band during visual short-term memory},
year = {2009},
month = {10},
volume = {39},
number = {652.20},
abstract = {Both extrastriate area V4 and the lateral prefrontal cortex (PF) are thought to be part of a neural network contributing to sensory and mnemonic processing of visual information. However, it is not well understood how V4 and PF might interact during visual memory. Here, we addressed this question by recording Local Field Potentials (LFP) simultaneously in both brain regions while two rhesus monkeys performed a delayed matching-to sample task. In the task, a sample stimulus (250ms) was presented followed by a probe stimulus (600ms) after a delay period (1500ms). A lever press was required if the sample stimulus matched the probe. We assessed coupling between LFP sites within and between the different brain regions by both measuring pair-wise phase-synchrony (phase locking value, PLV) using a wavelet based method and employing a coupling measure that relies on the concept of Granger causality (partial-directed coherence; PDC) using multivariate autoregressive (MVAR) modeling. In both monkeys we consistently found increases in theta-band phase synchrony (3.5-7 Hz) between V4 and PF LFP site pairs during the delay period of the task. Specifically, a significant proportion of pairs (26.1%, 62/231 for monkey 1 and 25%, 40/160 for monkey 2, p<0.001) showed increased coherence during the delay phase compared to the pre-stimulus baseline period. In contrast, only a small proportion of sites showed significant coupling in gamma (42-97 Hz, 5.9%/13% for monkeys 1/2, respectively) or beta (16-36Hz, 6.9%/16%) frequencies. In addition, we obtained comparable results using PDC, which also assesses the directionality of information flow between the brain areas. Our preliminary results indicate that the interaction between V4 and PF during short-term memory might be primarily mediated through neuronal coherence in the theta band. Furthermore, our analyses using MVAR modeling suggest that this interaction can be characterized by a bidirectional information flow between these areas. These findings support the idea that long-range interactions play an important role in short-term maintenance of short-term memory.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=470634df-7320-4970-9e75-ce2987d333c8&cKey=e8f7383e-257d-423d-b223-dd1788dbfe5f},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Liebe S{sliebe}{Department Physiology of Cognitive Processes}, Hoerzer G, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Maass W and Rainer G{gregor}}
}

@Poster{ 6090,
title = {Neuronal coding challenged by memory load in prefrontal cortex},
year = {2009},
month = {10},
volume = {39},
number = {282.5},
abstract = {As most cortical neurons are broadly tuned to various stimulus parameters, it is inevitable that individual neurons participate in the representation of more than one visual object. We asked here whether the prefrontal representation of immediately preceding objects would interfere with the representation of subsequently processed object stimuli, supporting the idea that neuronal processes challenged by more input and compressed in time leads to a degradation of the quality of encoding. In the past, we analyzed simultaneously recorded multi- and single-unit signals derived from arrays of single-ended microelectrodes and tetrodes during a simple visual memory task (SfN 2007 and 2008) and found that accurate representations of individual objects require the participation of large neuronal populations. Based on single trial firing rate values, we calculated one-way ANOVAs at 1% significance thresholds and performed subsequent posthoc comparisons (Scheffé) in order to detect stimulus selectivity and stimulus specificity for the activity at each single site, respectively. With tetrodes we were able to detect highly-specific units in PFC with a narrow band of stimulus preferences, which were remarkably stable throughout all stimulus comparisons. In order to increase the probability to find more of these specific units, we sharpened the impact and enhanced the temporal structure of the task. Two monkeys, who were trained to perform the basic task at ~80% performance, were ad hoc presented with a sequence of up to 4 objects that were shown consecutively within a fixed period of 900 ms. Not only the monkeys were able to impromptu generalize from a simple (Load 1) to a demanding task (Load 2-4) (Wildt et al., SfN 2008), they also showed highly selective sites (p< .009- p< 7 × 10-13) in all four load conditions, even for those last objects during load 4 (p<.006) which were presented for less than 250 ms. For all load conditions, highly specific sites could be found (118 pairwise comparisons with p<.01). One group of these sites kept their object preference throughout the entire sequence of all four objects, others responded position-dependent to different objects, but were still highly stable throughout all pairwise comparisons.
These results suggest that neuronal ensembles in primate PFC are capable of encoding up to 4 objects without interactions among the activity expressed in relation to other objects in the sequence. In addition, they are able to resolve even very shortly presented objects (<250 ms) showing strong selectivity uniquely for one of them and without superimposing this representation with signals evoked by more recently perceived objects.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=938a2530-b458-4d5b-9a55-d9c6ae61984e&cKey=68ed0dc6-293f-487d-a444-1e96bf9c4cd6&mKey={081F7976-E4CD-4F3D-A0AF-E8387992A658}},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Waizel M{waizel}{Department Physiology of Cognitive Processes}, Franke F, Pipa G, Chen N-H, Muckli L and Munk MHJ{munk}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6088,
title = {Neuronal coding challenged by memory load in prefrontal cortex},
journal = {Frontiers in Computational Neuroscience},
year = {2009},
month = {10},
volume = {2009},
number = {Conference Abstract: Bernstein Conference on Computational Neuroscience},
abstract = {As most cortical neurons are broadly tuned to various stimulus parameters, it is inevitable that individual neurons participate in the representation of more than one visual object. We asked here whether the prefrontal representation of immediately preceding objects would interfere with the representation of subsequently processed object stimuli, supporting the idea that neuronal processes challenged by more input and compressed in time leads to a degradation of the quality of encoding. In the past, we analyzed simultaneously recorded multi- and single-unit signals derived from arrays of single-ended microelectrodes and tetrodes during a simple visual memory task (Waizel et al., SfN 2007&2008) and found that accurate representations of individual objects require the participation of large neuronal populations. Based on single trial firing rate values, we calculated one-way ANOVAs at 1% significance thresholds and performed subsequent posthoc comparisons (Scheffé) in order to detect stimulus selectivity and stimulus specificity for the activity at each single site, respectively. With tetrodes we were able to detect highly-specific units in PFC with a narrow band of stimulus preferences, which were remarkably stable throughout all stimulus comparisons. In order to increase the probability to find more of these specific units, we sharpened the impact and enhanced the temporal structure of the task. Two monkeys, who were trained to perform the basic task at ~80% performance, were ad hoc presented with a sequence of up to 4 objects that were shown consecutively within a fixed period of 900 ms. Not only the monkeys were able to impromptu generalize from a simple (Load 1) to a demanding task (Load 2-4) (Wildt et al., SfN 2008), they also showed highly selective sites (p< .009- p< 7 × 10-13) in all four load conditions, even for those last objects during load 4 (p<.006) which were presented for less than 250 ms. For all load conditions, highly specific sites could be found (118 pairwise comparisons with p<.01). One group of these sites kept their object preference throughout the entire sequence of all four objects, others responded position-dependent to different objects, but were still highly stable throughout all pairwise comparisons.
These results suggest that neuronal ensembles in primate PFC are capable of encoding up to 4 objects without interactions among the activity expressed in relation to other objects in the sequence. In addition, they are able to resolve even very shortly presented objects (<250 ms) showing strong selectivity uniquely for one of them and without superimposing this representation with signals evoked by more recently perceived objects.},
web_url = {http://www.frontiersin.org/10.3389/conf.neuro.10.2009.14.084/event_abstract},
event_name = {Bernstein Conference on Computational Neuroscience (BCCN 2009)},
event_place = {Frankfurt a.M., Germany},
state = {published},
DOI = {10.3389/conf.neuro.10.2009.14.084},
author = {Waizel M{waizel}{Department Physiology of Cognitive Processes}, Franke F, Chen N-H, Pipa G, Muckli L, Obermayer K and Munk MHJ{munk}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6089,
title = {Prefrontal firing rates reflect the number of stimuli processed for visual short-term memory},
journal = {Frontiers in Computational Neuroscience.},
year = {2009},
month = {10},
volume = {2009},
number = {Conference Abstract: Bernstein Conference on Computational Neuroscience},
abstract = {The way a system reacts to increased task demands can reveal information about its functional mechanism. We therefore assessed the question how non human primates process information about visual stimuli by driving two rhesus monkeys to their cognitive limits in a visual memory task. The monkeys were first trained to successfully perform the visual memory task (> 80% correct responses). Then the number of stimuli shown to the monkey (load) was increased to up to 4. The stimulus presentation period (SP) was 900 milliseconds long. Thus, in the load 4 condition each single stimulus was only shown for less than 225ms. After a three second delay period, a test stimulus was shown. The task of the monkey was then to decide via differential button press, whether the test stimulus matched any of the previously shown stimuli. Neuronal firing rates were recorded using up to 16 multi electrodes placed in the prefrontal cortex. For every trial in which the monkey responded correctly, the average multi unit rate during the SP was estimated.
We then assessed the question whether the firing rates in the SP during the distinct load conditions were significantly different. To minimize the effect of non-stationarities present in the data, we paired the data so that the trials of one pair were maximally 2.5 minutes apart. We tested against the null-hypothesis that the firing rates during the SP did not differ significantly among the load conditions using the nonparametric Friedman-test for paired data. For every recording site where we could reject the null-hypothesis (p<0.05), we investigated in which direction the rates of the different load conditions differed, correcting for multiple tests using the Tukey-Kramer-correction. A total of 12681 correct trials were recorded with a total of 160 recording positions (6 to 16 per session). In total, 23 positions showed significant effects from which 20 were consistent. The firing rate differences were called consistent if the difference compared to load 1 were stronger the higher the load. Out of these 20 consistent recording sites 14 showed a firing rate which monotonically increased with the load, 6 showed a monotonous decrease. This means that 12% of the recording sites in prefrontal cortex show a significant modulation of firing rates with respect to the load condition during a delayed match to sample task. However this modulation is not necessarily excitatory. Interestingly, it seems that the majority of sites showed a load-consistent modulation i.e. the higher the load, the stronger the modulation. This could be a possible mechanism to code the number of stimuli or their sequence.},
web_url = {http://www.frontiersin.org/10.3389/conf.neuro.10.2009.14.106/event_abstract},
event_name = {Bernstein Conference on Computational Neuroscience (BCCN 2009)},
event_place = {Frankfurt a.M., Germany},
state = {published},
DOI = {10.3389/conf.neuro.10.2009.14.106},
author = {Franke F, Natora M, Waizel M{waizel}{Department Physiology of Cognitive Processes}, Muckli LF, Pipa G and Munk MHJ{munk}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6091,
title = {Prefrontal firing rates reflect the number of stimuli processed for visual short-term memory},
year = {2009},
month = {10},
volume = {39},
number = {480.10},
abstract = {The way a system reacts to increased task demands can reveal information about its functional mechanism. We therefore assessed the question how non human primates process information about visual stimuli by driving two rhesus monkeys to their cognitive limits in a visual memory task. The monkeys were first trained to successfully perform the visual memory task (> 80% correct responses). Then the number of stimuli shown to the monkey (load) was increased to up to 4. The stimulus presentation period (SP) was 900 milliseconds long. Thus, in the load 4 condition each single stimulus was only shown for less than 225ms. After a three second delay period, a test stimulus was shown. The task of the monkey was then to decide via differential button press, whether the test stimulus matched any of the previously shown stimuli. Neuronal firing rates were recorded using up to 16 multi electrodes placed in the prefrontal cortex. For every trial in which the monkey responded correctly, the average multi unit rate during the SP was estimated. We then assessed the question whether the firing rates in the SP during the distinct load conditions were significantly different. To minimize the effect of non-stationarities present in the data, we paired the data so that the trials of one pair were maximally 2.5 minutes apart. We tested against the null-hypothesis that the firing rates during the SP did not differ significantly among the load conditions using the nonparametric Friedman-test for paired data. For every recording site where we could reject the null-hypothesis (p<0.05), we investigated in which direction the rates of the different load conditions differed, correcting for multiple tests using the Tukey-Kramer-correction.
A total of 12681 correct trials were recorded with a total of 160 recording positions (6 to 16 per session). In total, 23 positions showed significant effects from which 20 were consistent. The firing rate differences were called consistent if the difference compared to load 1 were stronger the higher the load. Out of these 20 consistent recording sites 14 showed a firing rate which monotonically increased with the load, 6 showed a monotonous decrease. This means that 12% of the recording sites in prefrontal cortex show a significant modulation of firing rates with respect to the load condition during a delayed match to sample task. However this modulation is not necessarily excitatory. Interestingly, it seems that the majority of sites showed a load-consistent modulation i.e. the higher the load, the stronger the modulation. This could be a possible mechanism to code the number of stimuli or their sequence.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=0d31ed88-35b3-442a-a584-a68db14a1222&cKey=542ff937-0670-45e3-a7c9-034f64000ab0&mKey={081F7976-E4CD-4F3D-A0AF-E8387992A658}},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Franke F, Natora M, Waizel M{waizel}{Department Physiology of Cognitive Processes}, Muckli L, Pipa G, Obermayer K and Munk MHJ{munk}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6290,
title = {Primary visual cortex contributions in perceptual supppression},
year = {2009},
month = {10},
volume = {39},
number = {805.4},
abstract = {Understanding the neural underpinnings of conscious perception has long intrigued the students of the brain from philosophers to modern neuroscientists. In the visual domain, the primary visual cortex (V1) is by far the most extensively studied cortical area. It entails the main gateway of visual information to higher cortical areas and we understand a lot about its function in sensory processing. Nevertheless, the role of V1 in perceptual awareness remains intensely debated. Under certain stimulus conditions perception alternates between two or multiple stimulus interpretations. Notably such perceptual alternations happen while the sensory input is kept constant, offering thus a clear dissociation of sensory stimulation and subjective awareness. A celebrated example of such a perceptual phenomenon is binocular rivalry (BR). It involves the dichoptic presentation of two different stimuli at corresponding retinal locations and results in the perceptual suppression of one of the two stimuli at different times. A slight variant of BR, binocular flash suppression (BFS), ensures excellent control over the subjects’ perceptual state by intermittent presentation of monocular and binocular stimuli. We have trained rhesus macaques to report their perception during BFS and BR to study the effects of perceptual suppression in V1. We have recorded the spiking activity of a large number of well isolated single units (SUA) and acquired simultaneous local field potentials (LFPs) during the dichoptic presentation of orthogonal orientation gratings. We found that during BFS, 20% of the single units modulated their activities in consonance with the perceptual state. Furthermore, the magnitude of the perceptual effect was small (15%) in comparison to the sensory preference of the neurons. Analysis of the ocularity preferences demonstrated that both monocular and binocular classes of cells show perceptual modulations with equal probability. In addition, cells modulating during perceptual suppression encode information matching their sensory preferences and therefore can be used for decoding both the orientation and/or the eye of presentation of the perceived grating. Results of the LFPs were very similar to the single units showing a similar percentage of sites modulating with perception in all analyzed frequency bands. We conclude that footprints of perception are evident in both the SUA and LFP signals in V1 but in a much smaller degree than their corresponding sensory selectivity. Perceptual states might have a modulatory role on more intricate aspects of V1 firing patterns, not necessarily altering the firing rates of single cells or the LFP power dramatically.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=b32a2863-3104-401e-a2e7-5263bb970bc4&cKey=32ca0e40-6724-42ff-90dd-e00783866960},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Keliris GA{george}{Department Physiology of Cognitive Processes}, Tolias AS{atolias}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6285,
title = {Revealing polysynaptic propagation of excitation by microstimulation-fMRI of the deep cerebellar nuclei},
year = {2009},
month = {10},
volume = {39},
number = {367.21},
abstract = {The CNS consists of a large number of neurons organized in different brain regions and connected into a complex network. Studies of the connectivity of the brain has emphasized the point to point direct connections between brain regions. However, it has often been argued that in principle only a few synaptic steps are required to propagate activity from any location in the brain to any other. Hence not surprisingly questions regarding the efficacy, gating properties and coincident activation have become important issues as to how activity is propagated polysynaptically. The advent of the method of esfMRI - combining electrical stimulation with fMRI - has provided us with a new method to study the connectivity in spatially distributed networks. Here we show that electrical stimulation of the deep cerebellar nuclei (DCN) reveals BOLD responses in different brain sites that are only indirectly connected to the stimulation site, in fact we observe BOLD responses in brain sites that are dislodged away by at least three synaptic steps from the DCN. Hence we show that some neuronal pathways can propagate synchronous stimuli effectively and can lead to the activity of widespread brain regions via polysynaptic pathways that have not been considered so far. These findings are in marked contrast to our previous observations of a lack of propagation of electrically induced activation when stimulating neocortical brain sites (Tolias et al. 2005). Hence, our findings point to surprisingly divergent behaviours in different networks in their ability to propagate synchronous activity. We speculate that under physiological conditions these excitable subcortical networks are controlled by the inhibition of the cerebellar cortex which in our experiments is short-circuited by electrical stimulating the DCN.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=aa77b529-16c6-4a04-9bcb-f2d0780872b0&cKey=21bfa24c-ac10-43f7-9822-9a476aaa6d19},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Sultan FR, Augath M{mark}{Department Physiology of Cognitive Processes}, Hamodeh S, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Thier P and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6164,
title = {Smart Calcium-sensitive MRI Agents},
year = {2009},
month = {10},
web_url = {http://www.we-heraeus-stiftung.de/index.html},
event_name = {442. Wilhelm und Else Heraeus-Seminar "Molecular Imaging"},
event_place = {Bad Honnef, Germany},
state = {published},
author = {Angelovski G{goran}{Department Physiology of Cognitive Processes}, Chauvin T, Fouskov{\'a} P, Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, Canals S{canals}, Pohmann R{rolf}, T{\'o}th {\'E} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6284,
title = {Spatial and spectral aspects of saccade-related neuronal modulation in monkey lateral temporal cortex},
year = {2009},
month = {10},
volume = {39},
number = {263.14},
abstract = {Modulation of neural signals by saccadic eye movements (SEMs) has been reported in various cortical regions involved in visual and auditory perception. This work typically focused on how a SEM-related signal could prepare sensory areas for novel incoming visual stimuli following the end of SEMs [1]. In contrast to a low-dimensional timing signal, SEM modulation could convey information about the size and direction of SEMs, which could be useful for predicting what types of visual information to expect based on peripheral vision. Indeed, the local field potential (LFP) from visual areas V4 and TE in monkeys showed SEM modulation that was different for contra- and ipsi-versive horizontal SEMs [2]. In addition, single unit activity in primate auditory cortex is known to be sensitive to eye position in the orbit, as measured during spontaneous and auditory-evoked responses [4]. Our previous results showed that the upper bank superior temporal sulcus (STS) and core and belt auditory cortex (ACx) are modulated by SEMs [3], though it was not clear whether this was only a low-dimensional timing signal, or whether the response was also sensitive to the direction and/or magnitude of the saccade. Because oculomotor brain regions that project to STS and ACx are known to encode saccade amplitude while also controlling contraversive SEMs, we measured the influence of these two saccade metrics on ACx and STS activity in two awake, behaving monkeys during visually- and non-visually- guided SEMs. We analyzed the frequency-specific (spectral) LFP with a combination of Hilbert transforms and the Chronux signal processing toolbox. During SEMs, spectral power in the gamma and very high frequency ranges (60-200Hz) was correlated with the degree of contraversive movement and with overall saccade amplitude. The relationship between high-frequency power and saccade measures was seen in STS and ACx, during both visually-driven and non-visually-driven SEMs. In addition, high-frequency increases in power were often accompanied by decreases of power in the delta band (1-4 Hz). Our results suggest SEM modulation of activity in ACx and STS contains both spatial and temporal information, regardless of whether the SEM is visually-driven. Such a signal could be useful for scale-invariant feature integration, for the trans-saccadic integration of objects in complex scenes, or it may merely be the consequence of the signals conveyed from ipsilateral oculomotor areas.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=ffd23415-4aef-44f2-9390-a20a63e0c59f&cKey=7ac99a35-4a1b-441f-a39c-8010aaeb23f3},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Bartlett AM, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Hoffman KL{kari}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6159,
title = {Task-dependent co-modulation of different EEG rhythms in the non-human primate},
journal = {Frontiers in Computational Neuroscience},
year = {2009},
month = {10},
volume = {2009},
number = {Conference Abstract: Bernstein Conference on Computational Neuroscience},
abstract = {EEG signals are the most global brain signals which reflect a brain’s functional state, primarily by the frequency composition of oscillatory signal components. Numerous studies have shown that oscillations accompany many neuronal processes underlying cognitive function. Although the role of particular frequency bands is starting to emerge, their combined occurrence and dynamical interplay is scarcely understood with respect to their topological impact on neuronal processes. We set out to determine temporal and spatial properties of various EEG rhythms in the best established animal model for studying the neuronal mechanisms of cognition. Two monkeys were trained to perform a visuomotor task, moving a lever as instructed by a moving visual stimulus while fixation was maintained. At the end of each successful trial, a liquid reward was given and the monkey was waiting for the next trial to start. EEG was recorded from 64 electrodes chronically implanted in the bone bilaterally above numerous cortical areas: visual, auditory, parietal, sensorimotor, premotor and prefrontal areas, digitized at 5 kHz and analyzed for changes in signal power by sliding window FFT. These EEG signals are characterized by a broad distribution of oscillation frequencies, ranging from delta (1-3 Hz) to high gamma frequencies (>150 Hz). Different epochs of the task exhibited continual coming and going of prominent power clusters in the time-frequency domain. Reliable effects (z-scores > 2) could be observed in both monkeys: when attending the visual stimulus and precisely controlling the lever position, a prominent beta rhythm (12-30 Hz) occurred with a latency of 240 ms to the visual stimulus. As soon as the monkey initiated further lever movements, this beta rhythm was replaced by prominent power in the delta and in the high gamma band (50-140 Hz). The topography of the frequency bands differed: while beta oscillations could be seen mostly over visual, parietal and premotor areas, the delta band dominated for prefrontal and premotor electrodes and gamma rhythms were observed over prefrontal areas. In contrast, the period just after reward was dominated by power in the alpha band (8-13 Hz) distributed over the entire brain. In sum, we identified task-dependent EEG oscillations in diverse frequency bands which alternated through the different stages of the task following their typical topographical distributions. The observation that different EEG rhythms like in the delta and gamma frequency band co-occurred repeatedly suggests that interactions across frequencies might play a crucial role in processing task relevant information.},
web_url = {http://www.frontiersin.org/10.3389/conf.neuro.10.2009.14.164/event_abstract},
event_name = {Bernstein Conference on Computational Neuroscience (BCCN 2009)},
event_place = {Frankfurt a.M., Germany},
state = {published},
DOI = {10.3389/conf.neuro.10.2009.14.164},
author = {Rulla S{rulla} and Munk MJH{munk}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6160,
title = {Task-dependent co-modulation of different EEG rhythms in the non-human primate},
year = {2009},
month = {10},
volume = {39},
number = {759.1},
abstract = {EEG signals are the most global brain signals which reflect a brain’s functional state, primarily by the frequency composition of oscillatory signal components. Numerous studies have shown that oscillations accompany many neuronal processes underlying cognitive function. Although the role of particular frequency bands is starting to emerge, their combined occurrence and dynamical interplay is scarcely understood with respect to their topological impact on neuronal processes. We set out to determine temporal and spatial properties of various EEG rhythms in the best established animal model for studying the neuronal mechanisms of cognition. Two monkeys were trained to perform a visuomotor task, moving a lever as instructed by a moving visual stimulus while fixation was maintained. At the end of each successful trial, a liquid reward was given and the monkey was waiting for the next trial to start. EEG was recorded from 64 electrodes chronically implanted in the bone bilaterally above numerous cortical areas: visual, auditory, parietal, sensorimotor, premotor and prefrontal areas, digitized at 5 kHz and analyzed for changes in signal power by sliding window FFT. These EEG signals are characterized by a broad distribution of oscillation frequencies, ranging from delta (1-3 Hz) to high gamma frequencies (>150 Hz). Different epochs of the task exhibited continual coming and going of prominent power clusters in the time-frequency domain. Reliable effects (z-scores > 2) could be observed in both monkeys: when attending the visual stimulus and precisely controlling the lever position, a prominent beta rhythm (12-30 Hz) occurred with a latency of 240 ms to the visual stimulus. As soon as the monkey initiated further lever movements, this beta rhythm was replaced by prominent power in the delta and in the high gamma band (50-140 Hz). The topography of the frequency bands differed: while beta oscillations could be seen mostly over visual, parietal and premotor areas, the delta band dominated for prefrontal and premotor electrodes and gamma rhythms were observed over prefrontal areas. In contrast, the period just after reward was dominated by power in the alpha band (8-13 Hz) distributed over the entire brain. In sum, we identified task-dependent EEG oscillations in diverse frequency bands which alternated through the different stages of the task following their typical topographical distributions. The observation that different EEG rhythms like in the delta and gamma frequency band co-occurred repeatedly suggests that interactions across frequencies might play a crucial role in processing task relevant information.},
web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=aed4a8df-c183-4da1-9ec4-b0e7ccb96655&cKey=f66bad88-3526-48a6-b8de-526f0d302915&mKey={081F7976-E4CD-4F3D-A0AF-E8387992A658}},
event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)},
event_place = {Chicago, IL, USA},
state = {published},
author = {Rulla S{rulla} and Munk M{munk}{Department Physiology of Cognitive Processes}}
}

@Poster{ JoshiME2009,
title = {Comparison of a lipid- vs. peptide-based delivery system for intracellular targeted MR imaging probes},
year = {2009},
month = {9},
volume = {2009},
number = {0647},
abstract = {Magnetic Resonance Imaging (MRI) is meanwhile one of the most important medical diagnostic tools. Its specificity and sensitivity can be further extended by contrast agents (CAs). As many clinically valuable targets like DNA, mRNA or protein/enzymes reside inside the cell membrane, development of efficient intracellular targeted MR CA is required. However, prerequisite for intracellular targeting is not only the efficient delivery inside the cell but also the co-localization with the target. Recently, cell penetrating peptides (CPP) are used to achieve an efficient uptake of cargo molecules. However, it has been shown that these conjugates were predominantly taken up by an endosomal mechanism preventing a proper interaction with targets located in the cytosol. Cholesterol coupling has been reported to facilitate cellular import of siRNAs for effective silencing of protein expression [1]. We developed a contrast agent based on a lipid mediated delivery system by using cholesterol. Uptake and MR contrast enhancement ability was compared with a CPP based CA previously reported by our group [2]. To image the presence of specific mRNAs the probes composed of Gd-DOTA, FITC, a sequence to bind to target mRNA (DsRed), and CPP (D-Tat) or cholesterol for cellular delivery. Fmoc continuous solid phase chemistry was used for synthesis. Fluorescence and MR studies were performed using a mouse fibrosarcoma cell line expressing DsRed protein and its parent cell line deficient of the target sequence. Fluorescence spectroscopy showed that the CPP based CA (CPP-CA) could enter efficiently in both cell types without observable toxicity up to a concentration of 5μM. The cholesterol based CA (Chol-CA) was even more efficient. However, this conjugate was not soluble in aqueous solution at concentrations > 3µM. Both probes were able to enhance MRI contrast in labeled target containing as well as non-targeted parent cells. Intracellular relaxation rate increased already at a labeling concentration of 1µM for CPP-CA and 0.5µM for Chol-CA. However, fluorescence microscopy demonstrated that Chol-CA was also predominantly localized inside endosomes. Coupling of cholesterol further improved uptake and contrast enhancement. However, the reduced solubility in physiological aqueous media is restricting the applicability for MR imaging purposes. In addition, endosomal entrapment poses a still unsolved problem. Modifications to circumvent both drawbacks have to be implemented to achieve a sufficient cytosolic distribution of CA.},
web_url = {http://www.wmicmeeting.org/abstracts/data/papers/0647.html},
event_name = {2009 World Molecular Imaging Congress (WMIC)},
event_place = {Montréal, Canada},
state = {published},
author = {Joshi R{raju}{Department High-Field Magnetic Resonance}, Mishra R{ritu}{Department High-Field Magnetic Resonance} and Engelmann J{joern}{Department High-Field Magnetic Resonance}}
}

@Poster{ DhingraMESCPBML2009,
title = {Development of Bio-responsive Contrast Agents for Magnetic Resonance Imaging: Potential Applications of a Novel Precursor},
year = {2009},
month = {9},
volume = {2009},
number = {0617},
abstract = {Magnetic resonance imaging (MRI) is one of the powerful imaging modality. To circumvent its low sensitivity, there has been a substantial interest on the development of the contrast agents. In the present scenario, there is a need to develop contrast agents which are target specific and can report the changes in the physiological environment around them. On the similar lines we are reporting here a novel precursor (tris-tert-Bu-(Z)-Ser-DO3A (Figure 1)). This precursor contains an amine and a carboxylate groups in an orthogonally protected condition, which allows their selective de-protection and coupling to different moieties. Out of the various possibilities, we explored two strategies of coupling that lead to a potential targeted CA and another CA with potential of tracing neuroanatomy in the brain. The special design of these agents not only provides the stability against their enzymatic degradation which is important for their in vivo applicability but also has the possibility to amplify its signal once recognized by the target site. This could be done by exploiting the biotin/strept(avidin) high affinity and the pretargeting strategy, which is well established in nuclear medicine. The CA when bound to avidin showed an enhancement in the relaxivity (r1 and r2) at 1.5T. A substantial increase of ≥1000% in r2 was observed at all magnetic fields studied (1.5T, 3T, 7T, 9.4T) while r1 showed an increase of 260% at 1.5T and an expected decrease with further increase of field strength. The relaxivity changes at 1.5T suggest the structural requirement of a CA to fit in to avidin and optimize the parameters determining relaxivity of the complex matches well with our synthesized agent. Using the same precursor, we have also synthesized a CA which can potentially be used for tracing the neuronal tracks in the brain. Biocytin was used as the basic tracer. Coupling an MR detectable moiety to a well known neuroanatomical tracer would open up new possibilities to noninvasively study the neuronal networks by MRI.},
web_url = {http://www.wmicmeeting.org/abstracts/data/papers/0617.html},
event_name = {2009 World Molecular Imaging Congress (WMIC)},
event_place = {Montréal, Canada},
state = {published},
author = {Dhingra K{kirti}{Department Physiology of Cognitive Processes}, Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Engelmann J{joern}{Department High-Field Magnetic Resonance}, Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}, Canals S{canals}, Pohmann R{rolf}{Department High-Field Magnetic Resonance}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Maier ME and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ MishraDMSELC2009,
title = {Development of New In Vivo Gd-based Neuroanatomical Tracers for Magnetic Resonance Imaging},
year = {2009},
month = {9},
volume = {2009},
number = {0081},
abstract = {Gaining insights into brain function by identifying neuronal circuits connecting different regions of the brain is of prime interest in cognitive neuroscience. For visualization of anatomical connections, the tract-tracing technique has been proved to be an extremely useful tool which provides valuable information on afferent and efferent connectivity of the brain. A variety of neuroanatomical tracers exists, and numerous investigations using classical tracers have contributed valuable descriptions of connectivity in the mammalian brain (1). These studies, however, require fixed, histologically processed tissue for data analysis and therefore cannot be applied for noninvasive/longitudinal investigations. Manganese-enhanced Magnetic Resonance Imaging is a recently introduced non-invasive technique that represents the first effort in the direction of studying neuronal connectivity in vivo by means of MRI (2). It is based on the paramagnetic properties of Mn2+ ion and on the fact that, once taken up by neurons, Mn2+ is transported anterogradely along the axon. However, the technique presents several drawbacks that can challenge its applicability, the most important being the potential toxicity of the ion in the tissue. In this study, we have developed an entirely new tracing technique where we have synthesized stable and bifunctional neuronal tracers that allow both, in vivo brain connectivity studies by means of MRI and postmortem microscopic investigation in fixed tissue, in the same experimental animal. Existing tracer molecules with excellent tracing properties could be covalently connected to organic macrocyclic moiety caging gadolinium as MR reporter. We started with biocytin and biotinylated-dextranamine (BDA) as model molecules which are well known anterograde and also retrograde (as opposed to Mn2+) neuronal tracer. Due to high interaction of biotin-avidin, both tracers can be visualized in postmortem tissue by using a host of avidin conjugated markers at the light- and electron microscope level. We have performed in vitro cell studies in neuroblastoma cell lines to prove their uptake competence and in vivo MR/histological visualization to prove their in vivo tracing efficiency as potential neuroanatomical tract-tracers. Our results reveal that these new tracers allow for a new strategy of neuronal tract-tracing, combining the powerful spatial resolution of the conventional microscopic techniques and in vivo visualization by MRI. References. (1) Prog Neurobiol (2000), 62, 327 and (2) Neuroimage (2008), 40, 458.},
web_url = {http://www.wmicmeeting.org/abstracts/data/papers/0081.html},
event_name = {2009 World Molecular Imaging Congress (WMIC)},
event_place = {Montréal, Canada},
state = {published},
author = {Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Dhingra K{kirti}{Department Physiology of Cognitive Processes}, Mishra R{ritu}{Department High-Field Magnetic Resonance}, Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}, Engelmann J{joern}{Department High-Field Magnetic Resonance}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Canals S{canals}}
}

@Poster{ 6048,
title = {Encoding properties of neurons sensitive to species-specific vocalizations in the anterior temporal lobe of primates},
year = {2009},
month = {9},
volume = {3},
pages = {123-124},
abstract = {Human and monkey neuroimaging and monkey
electrophysiological studies suggest that neurons
in the anterior superior-temporal lobe are selective
for species-specific vocalizations. To better understand the basis of this selectivity, we studied
the coding properties of these neurons using
extracellular recordings in the awake macaque.
We used a paradigm based on a previous
macaque fMRI study to localize with electrophysiological
recordings a voice-sensitive region in
the anterior superior-temporal plane that prefers
species-specific vocalizations over other complex
sound categories. This revealed a cluster
of vocalization-preferring sites about 5mm anterior
to the tonotopically organized field RT. To
evaluate the neurons’ sensitivity to different vocal
components, we used a set of 12 species-specific
vocalizations and several acoustical manipulations
of these calls. These controls involved, 1)
preserved spectrum (PS) versions of the calls, 2)
preserved envelope (PE) versions, i.e., pink noise
shaped with the Hilbert extracted call envelope,
and 3) preserved spectrum and envelope (PSE)
versions, which combine the first-order spectral
and temporal characteristics of the calls, i.e., their
extracted frequency spectrum shaped with their
envelope (see Figure 1).
Comparing the responses to original calls and the
controls, only 29% of the units significantly preferred
one of these four categories, suggesting
that the responses of many neurons are robust
to our spectro-temporal manipulations. Of the
selective units, the majority (60%) favored the
preserved spectrum sounds (PS; Fig. 1), indicating
that these neurons are more sensitive to
spectral than temporal components. Yet, a linear
response classifier, inferring the identity of a vocalization
from a neuron’s single trial responses,
better decoded the original calls than the controls
in the population of neurons. In addition, we found
that the neurons are more selective for and more
sparsely encode the original calls than the acoustical
controls. Noteworthy, in comparison to previous
reports from the auditory core, belt, parabelt
and insular regions, the neurons in the anterior
superior-temporal plane were considerably more
selective to individual vocalizations (Fig. 1D).
We then tested whether these neurons encode
acoustical, phonetic, properties of calls or their
presumed functional meaning (semantics). More
units discriminated between acoustically different sounds belonging to a similar semantic category
(e.g., coo vs. grunt) than those that were acoustically
similar and from different semantic categories
(e.g., grunt vs. pant threat). These results
suggest that neuronal responses at this stage of
the auditory processing hierarchy are governed
by the acoustics of the calls.
In conclusion, evaluating single neuron responses
to the features of species-specific vocalizations
is clarifying the function of the voice-sensitive
regions of the primate brain. Although many of
the neurons did not prefer any specific call type,
they were selective for and could well decode
the species-specific vocalizations and their responses
revealed some preference for the spectral
features of the calls. Our findings suggest that
these neurons encode the acoustical features of
species-specific vocalization, such as the spectrum
of formant frequencies, which can provide
caller species and identity information perhaps
independently of a vocalization’s content.},
web_url = {http://www.auditory-cortex.de/assets/pdf/AC2009_Program_End.pdf},
event_name = {3rd International Conference on Auditory Cortex (AC 2009)},
event_place = {Magdeburg, Germany},
state = {published},
author = {Perrodin C{cperrodin}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Veit L{lveit}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Petkov C{chrisp}}
}

@Poster{ PanagiotaropoulosKKTL2009,
title = {High frequency local field potentials and multi unit activity reflect visual awareness in the macaque prefrontal cortex},
journal = {Frontiers in Behavioral Neuroscience},
year = {2009},
month = {9},
volume = {Conference Abstract: 41st European Brain and Behaviour Society Meeting},
abstract = {Binocular rivalry (BR) has been successfully combined with extracellular electrophysiological recordings in awake, behaving macaques to study the cortical mechanisms of subjective visual perception. Here we used binocular flash suppression (BFS), a highly controlled variant of BR, to explore the neuronal correlates of visual awareness in the inferior prefrontal convexity (icPFC) of the macaque brain while simultaneously recording multi unit activity (MUA) and local field potentials (LFP). We found that MUA was perceptually modulated in 67% of the visually selective recording sites. During BFS in 92% of MUA modulated sites we observed higher firing rates when the preferred stimulus was perceived. An explicit representation of the perceptually dominant stimulus was also provided by the power modulation of high frequency LFP’s only at the MUA modulated sites. Specifically, sensory selectivity of the LFP power increased as a function of frequency with the highest selectivity observed between 150 and 450Hz. The same pattern in LFP power selectivity was observed when the preferred stimulus was perceived during BFS. A correlation analysis between MUA and LFP power selectivity showed significant correlation in sensory selectivity for frequencies >60Hz that saturated at 150Hz and followed the same pattern during BFS.
While spikes measure cortical output, LFP’s are thought to reflect input and intracortical processing in a given cortical area. According to this scheme our results suggest that icPFC sites providing perceptually modulated output are also the sites that receive and process a representation of the perceived stimulus during BFS. Inferior temporal cortex (IT) output is also known to reflect the perceived stimulus during ambiguous visual stimulation and could thus be the source of the modulated icPFC input reflected in the LFP’s. Our results suggest a highly organized network involving IT and icPFC that mediates visual awareness during subjective visual perception.},
web_url = {http://www.frontiersin.org/10.3389/conf.neuro.08.2009.09.251/event_abstract},
event_name = {41st European Brain and Behaviour Society Meeting},
event_place = {Rhodos, Greece},
state = {published},
DOI = {10.3389/conf.neuro.08.2009.09.251},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Tolias A{atolias}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6167,
title = {Information breakdown analysis of simultaneous neural recordings: tools for the study of neural codes},
journal = {Frontiers in Neuroinformatics},
year = {2009},
month = {9},
number = {Conference Abstract: Neuroinformatics 2009},
abstract = {Information theory is becoming an increasingly popular framework for the study of sensory coding. Despite its widespread use for the analysis of single-cell spike trains, it has found relatively limited application to the analysis of other types of neurophysiological signals: This is due to the difficulty in estimating mutual information or entropies and to the lack of fast routines for the application of these techniques to multi-dimensional responses. Here we introduce our toolbox which allows to compute mutual information and other information theoretic quantities for the estimation of the information transmitted by different mechanisms of correlational coding. We also demonstrate the utility of our toolbox by applying it to the computation of the information conveyed by the power and phase of simulated and real Local Field Potentials and Electroencephalography.},
web_url = {http://frontiersin.org/conferences/individual_abstract_listing.php?conferid=155&pap=2130&ind_abs=1&pg=5},
event_name = {2nd INCF Congress of Neuroinformatics},
event_place = {Pilsen, Czech Republic},
state = {published},
DOI = {10.3389/conf.neuro.11.2009.08.097},
author = {Magri C{cmagri}{Department Physiology of Cognitive Processes}, Whittingstall K{kevin}{Department Physiology of Cognitive Processes}, Singh V{vsingh}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Poster{ 5885,
title = {Multisensory influences in auditory and superior temporal cortex},
year = {2009},
month = {9},
volume = {3},
pages = {100-101},
abstract = {Results from functional imaging and electrophysiology
suggest that responses in auditory cortex
can be modulated by stimulation of other sensory
modalities. In fact, auditory responses of neurons
in primary and secondary fields are enhanced
or reduced by the simultaneous presentation of
visual or touch stimuli. Although often denoted
as sensory integration, the exact function of
these multisensory influences is unclear, and it remains to be shown whether they actually make
the auditory neurons more reliable or informative
about the acoustic environment. To scrutinize the
neuronal basis of these multisensory influences,
we investigate mechanisms of neural information
coding in the auditory cortex of the macaque.
For just acoustic stimulation, we find that temporal
neural codes, such as precise spike timing,
or the relative firing of neurons to background
activity (phase of slow field potentials) provide
considerably more information than firing rates. In
addition, these different codes can encode complementary
information about the same stimulus
epochs. Overall, this suggests that the auditory
cortex might rely on the use of several neural
codes operating on different spatial temporal
scales at the same time.
In the context of multisensory stimuli, we find
that neurons become more informative about
the stimulus when an auditory stimulus is complemented
with the matching movie. Especially
the information in firing rates benefits from the
visual stimulation, while spike times show a rather
small information gain. In addition we find that
this information gain by multisensory stimulation
is not uniformly distributed across all stimuli, but
is highest for those stimuli which elicit strong
responses.
Overall our findings suggest that visual influences
in auditory cortex might be more than just
a simple response modulation, but make neuronal
firing more reliable, and hence enhance the
information encoded in auditory cortex about the
environment.},
web_url = {http://www.auditory-cortex.de/assets/pdf/AC2009_Program_End.pdf},
event_name = {3rd International Conference on Auditory Cortex (AC 2009)},
event_place = {Magdeburg, Germany},
state = {published},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Panzeri S{stefano} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6166,
title = {Non-vocal acoustic communication in macaques},
journal = {Frontiers in Behavioral Neuroscience},
year = {2009},
month = {9},
number = {Conference Abstract: 41st European Brain and Behaviour Society Meeting},
abstract = {Drumming is an activity practiced across all human cultures. Its origin, however, remains unknown. Drumming behavior is also displayed by non-human primates, such as chimpanzees and gorillas, suggesting that the underlying neural substrate has propagated through primate evolution. Here we describe a similar behavior in captive macaque monkeys: these animals use artificial objects in their environment to produce loud and repetitive sounds. Although these drumming sounds deviate in their acoustic properties much from typical vocal sounds, behavioral tests demonstrate that they serve as acoustic communication signals. First, in a preferential orienting task, naive subjects orient towards drumming sounds as frequently as to conspecific vocalizations but more than to other environmental sounds. Second, when drumming sounds are accompanied by a video of a conspecific animal, subjects clearly attempt to communicate with this individual, and when passively listening to such sounds individuals often show increased hea
rt rate, suggesting that these sounds evoke emotional responses. Third, on investigating the neural networks underlying the perception of these drumming sounds using fMRI, we find that drumming sounds activate the same networks that are otherwise specialized for processing vocal communication sounds. Together, our results suggest that drumming originated in non-human primates as a form of non-vocal acoustic communication.},
web_url = {http://frontiersin.org/conferences/individual_abstract_listing.php?conferid=154&pap=2444&ind_abs=1&pg=5},
event_name = {41st European Brain and Behaviour Society Meeting},
event_place = {Rhodos, Greece},
state = {published},
DOI = {10.3389/conf.neuro.08.2009.09.274},
author = {Remedios R{ryan}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Poster{ 6184,
title = {The effects of scopolamine on visual categorization in macaques},
year = {2009},
month = {9},
volume = {2009},
abstract = {Learning requires the ability to adapt to new situations and to respond to new categories of stimuli. This function is crucial in children and in adults and malfunction can lead to a debilitating disorder known as Alzheimer’s disease or senile dementia. Acetylcholine (ACh) is
one of several neuromodulators implicated in the brain’s adaptive behavior. It has an important role in several cognitive functions including attention, learning, short‐term memory and longterm memory. The Nucleus Basalis of Meynert supplies the cholinergic input to the neocortex
and shows marked cell loss in Alzheimer’s patients and in other cognitive disorders (Wernicke‐Korsakoff syndrome and Creutzfeldt‐Jakob disease).
We have examined the effects of scopolamine, an antagonist of muscarinic ACh receptors, on visual object recognition in macaques. Two macaques were taught a categorization task, i.e. to classify stimuli to categories by appropriate behavioral responses. The paradigm involved a task
during which an image that belonged to one of the categories was presented. The macaque used levers to categorize the stimulus.
Injections of scopolamine disrupted subsequent performance in this task. When the stimuli presented had not been seen before the experiment, scopolamine significantly impaired
categorization accuracy. The monkey was still able to carry out the task with a set of familiar stimuli, ie. stimuli that it had categorized successfully in previous sessions. Performance deteriorated as the stimulus became less salient by an increase in the level of visual noise.
Scopolamine, however, had at best a small effect on performance with familiar stimuli at the different noise levels.
ACh has a variety of effects, peripheral as well as central. In our attempt to localize the effects of
ACh we have used an analogue of scopolamine that cannot cross the blood brain barrier. The analogue (butyl scopolamine) mimicked the peripheral actions of scopolamine but caused no cognitive deficit. The cognitive changes, therefore, reflect ACh’s effect in the brain. The exact
site of the effect has not yet been established but is likely to depend on forebrain mechanisms.},
file_url = {/fileadmin/user_upload/files/publications/HSfN-2009-Aggelopoulos.pdf},
event_name = {23rd Meeting of the Hellenic Society for Neuroscience (HSfN)},
event_place = {Rhodos, Greece},
state = {published},
author = {Aggelopoulos NC{aggelopoulos}{Department Physiology of Cognitive Processes}, Liebe S{sliebe}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ 6156,
title = {Unusual Calcium Sensitivity of Aminobis(methylenephosphonate)-Containing MRI Contrast Agents},
year = {2009},
month = {9},
volume = {2009},
number = {0612},
abstract = {Calcium plays an important role in regulating a great variety of neuronal processes. A strong interest exists to generate gadolinium complexes which can act as calcium-sensors, in particular for magnetic resonance imaging (MRI). Here we report a new series of potential contrast agents based on DO3A, having an alkylaminobis(methylenephosphonate) side chain (propyl L1, butyl L2, pentyl L3 or hexyl L4). The complexation efficiency of the aminopolyphosphonic acid towards Ca2+, along with the ability to increase the presence of water in the secondary sphere and thus the longitudinal relaxivities (r1) of Gd3+-based CAs, was combined for potential use in sensing the extracellular calcium in the brain, especially at high field magnets. The paramagnetic response of the complexes GdL1-GdL4 was studied by means of relaxometric titrations at different Ca2+ concentrations. The initial relaxivities of the complexes were found to be higher than usually reported for the DO3A type ligands at high field magnets (9.4T). The r1 values of 6.92, 7.43, 6.70 and 5.76 mM-1s-1 were determined for GdL1, GdL2, GdL3, and GdL4 respectively. Interestingly the complexes exhibit unusual properties in the presence of Ca2+. The sensitivity of the complexes towards Ca2+ increases with the extension of the aliphatic side chain. In contrast to previously reported probes r1 decreases upon addition of Ca2+. No changes in r1 of GdL1 were found over the whole span of Ca2+ concentration. In the case of GdL2, a moderate decrease of r1 was observed upon addition of Ca2+, whereas r1 of the GdL3 and GdL4 solutions showed a strong dependency on the calcium concentration resulting in the decrease to 66% and 61% of the initial r1 values, respectively. This is favorable for novel fMRI techniques as it could allow transforming the decrease in extracellular Ca2+ concentration into a positive MR contrast during the neuronal activity. Financial support of the Max-Planck Society, the Hertie Foundation, the Louis-Jeantet Foundation and the Centre National de la Recherche Scientifique (CNRS, France) is gratefully acknowledged. J.H. thanks the Fonds der Chemischen Industrie for a PhD scholarship. This work has been performed within the frame of the European COST Action D38 “Metal-Based Systems for Molecular Imaging Applications”.},
file_url = {/fileadmin/user_upload/files/publications/SMI_2009_IM_Ca_[0].pdf},
web_url = {http://www.wmicmeeting.org/abstracts/data/papers/0612.html},
event_name = {2009 World Molecular Imaging Congress (WMIC)},
event_place = {Montréal, Canada},
state = {published},
author = {Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, Henig J, Angelovski G{goran}{Department Physiology of Cognitive Processes}, T{\'o}th {\'E}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Mayer HA{kama}}
}

@Poster{ 6049,
title = {Visual influences on voice-selective neurons in the anterior superior-temporal plane},
year = {2009},
month = {9},
volume = {3},
pages = {125},
abstract = {For social interaction and survival primates rely
heavily on vocal and facial communication signals
from their conspecifics. To date many studies have
evaluated the unisensory representations of either
vocal or facial information in regions thought to be
voice or face selective. Other studies have directly
evaluated the multisensory interactions of voices
and faces but have focused on posterior auditory
regions closer to the primary auditory cortex. This
work investigates multisensory interactions at the
neuronal level in an auditory region in the anterior
superior temporal plane, which contains one of
the regions important for processing voice-related
information.
Extracellular recordings were obtained from the
auditory cortex of macaque monkeys, targeting
an anterior voice region that we have previously
described with functional magnetic resonance
imaging (fMRI, Fig. 1A). For stimulation we used
movies of vocalizing monkeys and humans which
we matched in their low-level auditory and visual
features. These dynamic face and voice stimuli
allowed us to evaluate how neurons responded
to auditory, visual or audio-visual components of
the stimuli. Our experiments also contained control
conditions consisting of several mismatched audiovisual
stimuli combinations, such as 1) a voice
matched to a face from a different species, 2) adding
a temporal delay in the visual component of the
stimulus, or 3) using an acoustically manipulated
voice with the original facial stimulus.
Our neuronal recordings identified a clustered
population of voice-selective sites in the anterior superior temporal plane, ~5 mm anterior to the
tonotopically organized field RT (Fig. 1B). A significant
visual influence of the dynamic faces on
the corresponding (matched) vocalizations was observed
in both the local-field potential (LFP) and the
spiking activity (analog multiunit activity, AMUA):
38% of the sites showed audiovisual interactions
in the LFP signals, and 60% in the AMUA (Fig.
2). In addition, the multisensory influence was significantly
stronger for the matching voice and face
stimuli than to any of the incongruent (mismatched)
control conditions, confirming the specificity of the
cross-sensory influence on the neuronal activity.
Our results provide evidence for visual influences
in what has been characterized as an auditory
‘voice’ area. This visual modulation was specific for
behaviorally relevant voice-face associations and
demonstrates that the processing of voice-related
information in higher auditory regions is influenced
by multisensory input.},
web_url = {http://www.auditory-cortex.de/assets/pdf/AC2009_Program_End.pdf},
event_name = {3rd International Conference on Auditory Cortex (AC 2009)},
event_place = {Magdeburg, Germany},
state = {published},
author = {Perrodin C{cperrodin}{Department Physiology of Cognitive Processes}, Kayser C{kayser}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Petkov C{chrisp}}
}

@Poster{ 6100,
title = {Encoding of object and face categories by simultaneously recorded local field potentials and single cell activity in the inferior temporal cortex of the macaque monkey},
journal = {Perception},
year = {2009},
month = {8},
volume = {38},
number = {ECVP Abstract Supplement},
pages = {78},
abstract = {We investigate to which extent signals recorded from the inferior temporal (IT) cortex of two macaque monkeys can discriminate between (i) faces vs objects, and (ii) monkey vs human faces. During a fixation task, we simultaneously recorded the local field potential (LFP) and spiking activity of single cells at 202 different sites. On each site we computed (i) visual-evoked potentials (VEP), (ii) single-trial-based instantaneous power and phase for different frequency bands, and (iii) spiking activity of single neurons. Considering the VEPs, specifically the P100 deflection, we found that its onset latency occurred earlier for faces than for objects ( p < 0.01) and for monkey than for human faces ( p < 0.05). In contrast, the P100 amplitude did not systematically differentiate between these categories. In the frequency domain, we found that the amount of phase-locking (across trials in single electrodes) of the theta-band around the P100 discriminated between faces/objects and humans/monkeys. Finally, we found that differences in the amount of phase-locking of the gamma-band around P100 between faces/objects were significantly correlated with faces/objects selectivity of single neurons at those locations. Our findings provide novel insights into the neural mechanisms of object and face recognition.},
web_url = {http://www.perceptionweb.com/abstract.cgi?id=v090792},
event_name = {32nd European Conference on Visual Perception},
event_place = {Regensburg, Germany},
state = {published},
author = {Sigala R{sigala}{Department Physiology of Cognitive Processes}, Veit J{jveit}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ LiebeLR2009,
title = {Selectivity of local field potentials to natural images in primate V4 and prefrontal cortex},
journal = {Perception},
year = {2009},
month = {8},
volume = {38},
number = {ECVP Abstract Supplement},
pages = {37},
abstract = {Both the extrastriate area V4 and the prefrontal cortex (PF) play an important role in the processing of visual information. Their role can be understood by examining single unit activity as well as local field potential responses that are indicators of dendro-somatic events. Here we studied the interaction between luminance- and colour-based structural information in natural images on the tuning properties of local field potential responses in both cortical areas while monkeys were performing a visual recognition task. Our analyses focused on the stimulus-locked LFP waveforms (or visually evoked potential, VEP). In both areas, a majority of sites showed significant VEPs to natural images. In addition, our analysis revealed that VEP amplitudes in V4 were strongly modulated by colour, but not by structural content of the image. In contrast, amplitudes in prefrontal cortex were strongly modulated by image structure, irrespective of colour. These results suggest, that V4 is a highly colour sensitive area as measured by the LFP, whereas the LFP in PF cortex reflects the informational content of natural images.},
web_url = {http://www.perceptionweb.com/abstract.cgi?id=v090969},
event_name = {32nd European Conference on Visual Perception},
event_place = {Regensburg, Germany},
state = {published},
author = {Liebe S{sliebe}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ SeidelWMS2009,
title = {Detection of single trial power coincidence for the identification of distributed cortical processes in a behavioral context},
journal = {BMC Neuroscience},
year = {2009},
month = {7},
volume = {10},
number = {Suppl 1},
pages = {P332},
abstract = {The analysis of neuronal processes distributed across multiple cortical areas aims at the identification of interactions between signals recorded at different sites. Such interactions can be described by measuring the stability of phase angles in the case of oscillatory signals or other forms of signal dependencies for less regular signals. Before, however, any form of interaction can be analyzed at a given time and frequency, it is necessary to assess whether all potentially contributing signals are present.
We have developed a new statistical procedure for the detection of coincident power in multiple simultaneously recorded analog signals, allowing the classification of events as 'non-accidental co-activation'. This method can effectively operate on single trials, each lasting only for a few seconds. Signals need to be transformed into time-frequency space, e.g. by applying a short-time Fourier transformation using a Gaussian window. The discrete wavelet transform (DWT) is used in order to weight the resulting power patterns according to their frequency. Subsequently, the weighted power patterns are binarized via applying a threshold. At this final stage, significant power coincidence is determined across all subgroups of channel combinations for individual frequencies by selecting the maximum ratio between observed and expected duration of co-activation as test statistic. The null hypothesis that the activity in each channel is independent from the activity in every other channel is simulated by independent, random rotation of the respective activity patterns.
We applied this procedure to single trials of multiple simultaneously sampled local field potentials (LFPs) obtained from occipital, parietal, central and precentral areas of three macaque monkeys. Since their task was to use visual cues to perform a precise arm movement, co-activation of numerous cortical sites was expected. In a data set with 17 channels analyzed, up to 13 sites expressed simultaneous power in the range between 5 and 240 Hz. On average, more than 50% of active channels participated at least once in a significant power co-activation pattern (PCP). Because the significance of such PCPs can be evaluated at the level of single trials, we are confident that this procedure is useful to study single trial variability with sufficient accuracy that much of the behavioral variability can be explained by the dynamics of the underlying distributed neuronal processes.},
web_url = {http://www.biomedcentral.com/1471-2202/10/S1/P332},
event_name = {Eighteenth Annual Computational Neuroscience Meeting (CNS*2009)},
event_place = {Berlin, Germany},
state = {published},
DOI = {10.1186/1471-2202-10-S1-P332},
author = {Seidel A, Wibral M, Munk MHJ{munk}{Department Physiology of Cognitive Processes} and Schneider G}
}

@Poster{ 6053,
title = {Effects of TMS on visual evoked potentials in a visual suppression task},
journal = {NeuroImage},
year = {2009},
month = {7},
volume = {47},
number = {Supplement 1},
pages = {S63},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WNP-4X3PHYG-C5-1&_cdi=6968&_user=29041&_pii=S1053811909703131&_orig=search&_coverDate=07%2F31%2F2009&_sk=999529999.8998&view=c&wchp=dGLbVlb-zSkWz&md5=2470e848fa9c4374e77849be08a165d4&ie=/sdarticle.},
event_name = {15th Annual Meeting of the Organization for Human Brain Mapping (HBM 2009)},
event_place = {Melbourne, Australia},
state = {published},
DOI = {10.1016/S1053-8119(09)70313-1},
author = {Thielscher A{thielscher}{Department High-Field Magnetic Resonance}, Reichenbach A{areichen}{Department Human Perception, Cognition and Action}{Department High-Field Magnetic Resonance} and Whittingstall K{kevin}{Department Physiology of Cognitive Processes}}
}

@Poster{ MazzoniBKMLP2009,
title = {Information content and robustness of various types of codes in integrate and fire networks presented with naturalistic stimuli},
journal = {BMC Neuroscience},
year = {2009},
month = {7},
volume = {10},
number = {Suppl 1},
pages = {P95},
abstract = {Several candidate neural codes have been proposed to convey sensory information, from spike count to spike patterns, to the timing of spikes relative to oscillations in the Local Field Potential (LFP). Recent experimental studies compared the information content of different codes in V1 [1] and A1 [2]. A code combining the spike count and the phase of firing relative to the low frequency component of the LFP contained more information than spike count [1,2] and displayed also a higher robustness to noise [2]. Spike patterns also conveyed more information than the spike count over the same window [2].

An interesting question regards the mechanisms underlying the generation of such robust temporal codes. Here, we investigated to which extent randomly and sparsely connected recurrent networks of integrate-and-fire neurons [3] subject to naturalistic external stimulation [4] can generate precise and robust temporal codes. We injected the network with inputs built from multi-unit recordings in the LGN of anesthetized monkeys presented with naturalistic movies [4]. As in [2], we divided the recording time into windows and we computed the information content of i) the window spike count; ii) the window spike count combined with its phase relative to the low frequency component of the LFP; iii) the spike patterns obtained dividing the windows into bins of 4–8 ms; iv) the spike patterns combined with the phase.

We found that spike patterns of 3–4 bins conveyed up to 20% more information than spike count, that adding the phase of firing to the spike count increased information up to 100%, and that the combination of the two codes produced a further increase in the information content. Results are qualitatively similar to what was found in experimental recordings, suggesting that such temporal codes can be generated even in the absence of a particular network architecture. The robustness of these codes was then tested against different kinds of noise. When the inputs were injected with jitters of several ms, the information content of spike patterns decreased sharply while the phase of firing code was more robust than the spike count code. Conversely, spike pattern information was less affected than phase information by increases in the amplitude of the external noise. In recurrent networks, codes involving both spike patterns and phase of firing with respect to low frequency components of the LFP appear therefore to be both significantly more informative than simpler spike count codes and more robust to noise.},
web_url = {http://www.biomedcentral.com/1471-2202/10/S1/P95},
event_name = {Eighteenth Annual Computational Neuroscience Meeting (CNS*2009)},
event_place = {Berlin, Germany},
state = {published},
DOI = {10.1186/1471-2202-10-S1-P95},
author = {Mazzoni A, Brunel N, Kayser C{kayser}{Department Physiology of Cognitive Processes}, Magri C{cmagri}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Poster{ 5886,
title = {Multisensory influences in auditory and superior temporal cortex},
year = {2009},
month = {7},
volume = {10},
number = {814},
pages = {377},
abstract = {Recent results from human imaging and electrophysiology demonstrate that the processing of acoustic information can be influenced by stimulation of other sensory modalities already at early stages in auditory cortex. Here we scrutinize the neuronal basis of these multisensory influences at different stages along the auditory processing streams. To this end we record neuronal responses in different regions of auditory cortex and in the upper bank of the superior temporal sulcus (STS) during stimulation with naturalistic audio-visual stimuli.
In caudal primary or secondary auditory fields only few neurons revealed significant visual influences. However in regions beyond the classical auditory cortex, their fraction increased considerably, and in association regions such as the upper bank STS both bimodal neurons and neurons with significant multisensory interactions were common. In fact, our results demonstrate a spatial topographical layout of modality preferences in the STS, which might provide a neural basis of sensory integration in this region. To characterize the effect of multisensory inputs at each of these processing stages we investigate the importance of stimulus congruency on multisensory interactions. In addition, to distinguish basic response modulation from sensory integration we use methods of information theory to determine whether visual input actually enhances the information encoded by neuronal responses about the stimulus. Altogether, our results provide first insights into how the impact of multisensory influences increases along a sensory processing pathway and start to shed light on where and how the neural representation of the sensory environment benefits from multisensory inputs.},
web_url = {http://imrf.mcmaster.ca/IMRF/ocs/index.php/meetings/2009/paper/view/814},
event_name = {10th International Multisensory Research Forum (IMRF 2009)},
event_place = {New York, NY, USA},
state = {published},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Dahl C{dahl}{Department Physiology of Cognitive Processes}, Panzeri S{stefano} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ PriesemannWM2009,
title = {Neuronal avalanches recorded in the awake and sleeping monkey do not show a power law but can be reproduced by a self-organized critical model},
journal = {BMC Neuroscience},
year = {2009},
month = {7},
volume = {10},
number = {Suppl 1},
pages = {P161},
abstract = {Self-organized critical (SOC) systems are complex dynamical systems that may express cascades of events, called avalanches [1]. The SOC state was proposed to govern brain function, because of its activity fluctuations over many orders of magnitude, its sensitivity to small input and its long term stability [2,3]. In addition, the critical state is optimal for information storage and processing [4]. Both hallmark features of SOC systems, a power law distribution f(s) for the avalanche size s and a branching parameter (bp) of unity, were found for neuronal avalanches recorded in vitro [5]. However, recordings in vivo yielded contradictory results [6]. Electrophysiological recordings in vivo only cover a small fraction of the brain, while criticality analysis assumes that the complete system is sampled. We hypothesized that spatial subsampling might influence the observed avalanche statistics. In addition, SOC models can have different connectivity, but always show a power law for f(s) and bp = 1 when fully sampled. This may not be the case under subsampling, however. Here, we wanted to know whether a state change from awake to asleep could be modeled by changing the connectivity of a SOC model without leaving the critical state.
We simulated a SOC model [1] and calculated f(s) and bp obtained from sampling only the activity of a set of 4 × 4 sites, representing the electrode positions in the cortex. We compared these results with results obtained from multielectrode recordings of local field potentials (LFP) in the cortex of behaving monkeys. We calculated f(s) and bp for the LFP activity recorded while the monkey was either awake or asleep and compared these results to results obtained from two subsampled SOC model with different connectivity.
f(s) and bp were very similar for both the experiments and the subsampled SOC model, but in contrast to the fully sampled model, f(s) did not show a power law and bp was smaller than unity. With increasing the distance between the sampling sites, f(s) changed from "apparently supercritical" to "apparently subcritical" distributions in both the model and the LFP data. f(s) and bp calculated from LFP recorded during awake and asleep differed. These changes could be explained by altering the connectivity in the SOC model.
Our results show that subsampling can prevent the observation of the characteristic power law and bp in SOC systems, and misclassifications of critical systems as sub- or supercritical are possible. In addition, a change in f(s) and bp for different states (awake/asleep) does not necessarily imply a change from criticality to sub- or supercriticality, but can also be explained by a change in the effective connectivity of the network without leaving the critical state.},
web_url = {http://www.biomedcentral.com/1471-2202/10/S1/P161},
event_name = {Eighteenth Annual Computational Neuroscience Meeting (CNS*2009)},
event_place = {Berlin, Germany},
state = {published},
DOI = {10.1186/1471-2202-10-S1-P161},
author = {Priesemann V, Wibral M and Munk MHJ{munk}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5935,
title = {Semi-supervised Analysis of Human fMRI Data},
year = {2009},
month = {7},
abstract = {Kernel Canonical Correlation Analysis (KCCA) is a general technique for subspace learning that incorporates principal
components analysis (PCA) and Fisher linear discriminant analysis (LDA) as special cases. By finding directions
that maximize correlation, CCA learns representations tied more closely to underlying process generating the
the data and can ignore high-variance noise directions. However, for data where acquisition in a given modality is
expensive or otherwise limited, CCA may suffer from small sample effects. We propose to use semisupervised
Laplacian regularization to utilize data that are present in only one modality. This approach is able to find
highly correlated directions that also lie along the data manifold, resulting in a more robust estimate of correlated
subspaces.
Functional magnetic resonance imaging (fMRI) acquired data are naturally amenable to subspace techniques as data
are well aligned. fMRI data of the human brain are a particularly interesting candidate. In this study we implemented
various supervised and semi-supervised versions of CCA on human fMRI data, with regression to single and multivariate
labels (corresponding to video content subjects viewed during the image acquisition). In each variate condition,
the semi-supervised variants of CCA performed better than the supervised variants, including a supervised variant
with Laplacian regularization. We additionally analyze the weights learned by the regression in order to infer brain
regions that are important to different types of visual processing.},
file_url = {/fileadmin/user_upload/files/publications//fileadmin/user_upload/files/publications/pdf1236.pdfchen-b-1_[0].pdf},
web_url = {http://bbci.agilemeetings.com/},
event_name = {Berlin BCI Workshop 2009: Advances in Nanotechnology},
event_place = {Berlin, Germany},
state = {published},
author = {Shelton JA{jshelton}{Department Empirical Inference}, Blaschko MB{blaschko}{Department Empirical Inference}, Lampert CH{chl}{Department Empirical Inference} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6165,
title = {Monkeys Communicate by Drumming},
year = {2009},
month = {6},
abstract = {Drumming is an activity practiced across all human cultures. Its origin, however, remains unknown. Drumming behavior is also displayed by non-human primates, such as chimpanzees and gorillas, suggesting that the underlying neural substrate has propagated through primate evolution. Here we describe a similar behavior in captive macaque monkeys: these animals use artificial objects in their environment to produce loud and repetitive sounds. Although these drumming sounds deviate in their acoustic properties much from typical vocal sounds, behavioral tests demonstrate that they serve as acoustic communication signals. First, in a preferential orienting task, naive subjects orient towards drumming sounds as frequently as to conspecific vocalizations but more than to other environmental sounds. Second, when drumming sounds are accompanied by a video of a conspecific animal, subjects clearly attempt to communicate with this individual, and when passively listening to such sounds individuals often show increased hea
rt rate, suggesting that these sounds evoke emotional responses. Third, on investigating the neural networks underlying the perception of these drumming sounds using fMRI, we find that drumming sounds activate the same networks that are otherwise specialized for processing vocal communication sounds. Together, our results suggest that drumming originated in non-human primates as a form of non-vocal acoustic communication.},
web_url = {http://www.cimec.unitn.it/events/cogevo/09/},
event_name = {1st Workshop on Cognition and Evolution (CogEvo 2009)},
event_place = {Rovereto, Italy},
state = {published},
author = {Remedios R{ryan}{Research Group Physiology of Sensory Integration}, Nikos LK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Poster{ 5733,
title = {A triple-resonant RF coil setup for 1H, 23Na and 39K MR imaging of the rat brain at 9.4T},
year = {2009},
month = {4},
volume = {17},
number = {2471},
abstract = {The measurement of the spatial distribution of pathologically changing ion concentrations of 23Na and 39K could offer a very promising approach in clinical diagnostics. For MR imaging of both elements and the acquisition of anatomical proton images in the same experiment without moving the subject or the RF coil we developped a triple-resonant RF coil setup for the rat head at 9.4T. Two perpendicular Helmholtz pairs for 23Na and 39K delivered a good homogeneity over the sample volume. The flat double-D 1H surface coil showed no signs of coupling with the other coils and good coverage for shimming and anatomical images.},
file_url = {fileadmin/user_upload/files/publications/ISMRM-2009-02471.pdf},
web_url = {http://www.ismrm.org/09/},
event_name = {17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009)},
event_place = {Honolulu, HI, USA},
state = {published},
author = {Augath M{mark}{Department Physiology of Cognitive Processes}, Heiler P, Kirsch S and Schad LR}
}

@Poster{ RoseEMHELLP2009,
title = {A Web-Based Probabilistic Tractography Database},
year = {2009},
month = {4},
volume = {17},
number = {3552},
abstract = {Diffusion tensor imaging (DTI) and probabilistic tractography allow inferences to be made about connectivity in the brain. Tractography results are useful to a range of communities, from those working in MR, through biologists, psychologists and physicians. However, few who stand to benefit have ready access to the requisite MR scanners, sequences and tractography software. This abstract describes a new Internet-based system that allows researchers to obtain anatomical connectivity information—derived from DTI and probabilistic tractography—for a number of human and animal subjects. We provide a web browser-based interface suited to manual browsing, and a programmatic interface suited to batch processing.},
file_url = {fileadmin/user_upload/files/publications/ISMRM-2009-03552.pdf},
web_url = {http://www.ismrm.org/09/},
event_name = {17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009)},
event_place = {Honolulu, HI, USA},
state = {published},
author = {Rose CJ, Ellard D, Morris D, Haroon H, Embleton K, Logothetis NK{nikos}{Department Physiology of Cognitive Processes}, Lambon Ralph MA and Parker GJ}
}

@Poster{ UludagZGL2009,
title = {Calibrating the BOLD signal revisited – Calculation of oxygen metabolism for gradient- and spin-echo sequence up to 16.4T},
year = {2009},
month = {4},
volume = {17},
number = {3701},
abstract = {A BOLD signal model as a function oxygen extraction fraction and CBV was developed in order to determine change in oxidative metabolism from combined BOLD signal and CBF measurements. The new model is an alternative model to the widely used calibrated BOLD approach initally proposed by Davis and colleagues for GRE at 1.5T. The new model, however, takes also intra-vascular MRI signal into account and is developed for both GRE and SE from 1.5T up to 16.4T. In the current study, at 4.7T and 7T using SE and GRE, oxidative metabolism change during visual stimulation was determined in macaque monkeys.},
file_url = {fileadmin/user_upload/files/publications/ISMRM-2009-03701.pdf},
web_url = {http://www.ismrm.org/09/},
event_name = {17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009)},
event_place = {Honolulu, HI, USA},
state = {published},
author = {Uludag K{kuludag}, Zappe A-C{aczappe}{Department Physiology of Cognitive Processes}, Goense J{jozien}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ GoenseML2009,
title = {Comparison of Functional Activation in the Temporal Lobe of Awake and Anesthetized Monkeys},
year = {2009},
month = {4},
volume = {17},
number = {1602},
abstract = {The fMRI response to a movie stimulus was compared in the ventral visual pathway of awake and anesthetized macaques. The ventral visual stream is essential for object recognition and memory, and in awake monkeys large swaths of the pathway are activated. In anesthetized monkeys the temporal lobe also shows large areas of activation, corresponding to the areas in awake monkeys. It is reported difficult to elicit activation beyond early sensory areas, but our results show robust activation high in the visual pathway in areas involved in object recognition. The robust activation seen here is possibly due to the higher CNR at 7T.},
file_url = {fileadmin/user_upload/files/publications/ISMRM-2009-01602.pdf},
web_url = {http://www.ismrm.org/09/},
event_name = {17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009)},
event_place = {Honolulu, HI, USA},
state = {published},
author = {Goense J{jozien}{Department Physiology of Cognitive Processes}, Merkle H{hellmut} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6099,
title = {Neural encoding of face-categories in the macaque temporal cortex},
year = {2009},
month = {4},
web_url = {http://ec.europa.eu/information_society/events/fet/2009/programme/poster_sessions/index_en.htm},
event_name = {European Future Technologies Conference (FET 2009)},
event_place = {Praha, Czech Republic},
state = {published},
author = {Sigala Alanis GR{sigala}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ 6157,
title = {Relaxometric, Thermodynamic and Kinetic Studies of Lanthanide(III) Complexes of DO3A-based Propylphosphonates},
year = {2009},
month = {4},
pages = {212},
abstract = {Development of the responsive probes is one of the most exciting topics in the contrast agent research. Design of the pH sensitive probes, for example, can be an important issue in the early cancer diagnostic and formation of pH maps.[1] This can be reached by introduction of different functional groups such as phosphonates at the fourth nitrogen of the DO3A molecule. [2] Two DO3A-based ligands and their Gd3+ and Eu3+ complexes containing ethyl-protected and unprotected propylphosphonates in the side chain were investigated. Proton relaxometric in vitro studies at 20 MHz and 60 MHz and 37 °C of the Gd3+ complex containing free acid exhibited relative changes of up to 56% in r1 relaxivity when the pH of the medium was changed from 4 to 7. This change is explained by the increase in the number of coordinated water molecules from 1 to 2. Temperature dependent relaxivity and NMRD profiles of Gd3+ complexes showed a slightly increased rotational correlation time, which is characteristic of phosphonate-containing compounds. Thermodynamic and kinetic studies of the Gd3+ and Eu3+ complexes were performed by means of potentiometry and luminescence spectroscopy. The results indicate that the thermodynamic stability and kinetic inertness of these complexes are sufficient for their in vivo application.},
file_url = {/fileadmin/user_upload/files/publications/COST%20D38_Ilgar%20Mamedov_2009_[0].pdf},
web_url = {http://www.cost.eu/domains_actions/cmst/Actions/D38},
event_name = {CMST COST Action D38: Metal-Based Systems for Molecular Imaging Applications},
event_place = {Tübingen, Germany},
state = {published},
author = {Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, T{\'a}borsk{\'y} P, Lubal P, Laurent S, Elst LV, Logothetis N{nikos}{Department Physiology of Cognitive Processes} and Angelovski G{goran}{Department Physiology of Cognitive Processes}}
}

@Poster{ HoffmanTGL2009,
title = {Phase coding of faces and objects in the superior temporal sulcus},
journal = {Frontiers in Systems Neuroscience},
year = {2009},
month = {3},
volume = {Conference Abstract: Computational and Systems Neuroscience 2009},
abstract = {Phase coding - stimulus coding by the timing of spikes with respect to the phase of local oscillations - is an alternative, complementary coding strategy to that of rate coding. One neocortical mechanism for phase coding posits that rhythmic inhibition in the gamma frequency range may interact with stimulus-evoked excitation, producing spikes earlier in an oscillatory cycle for preferred than non-preferred stimuli (Fries et al. 2007). Thus, the enhanced response for preferred stimuli commonly seen in the slowly-evolving rate code may also be coded through differences in spike timing within a single gamma cycle. Theoretically, this would provide a downstream target with a faster readout than would be possible with rate coding. Evidence for phase coding of visual stimuli was demonstrated recently in V1 of the anesthetized macaque (Montemurro et al. 2008), but only for lower frequencies (<12 Hz). Another study of spike-field phase coding in the secondary somatosensory cortex of the awake monkey also failed to find phase coding in the gamma frequency range (Ray et al. 2008).
To address the generality and frequency-dependence of phase coding, we tested whether phase coding would be observed in an object-selective brain region in the awake macaque. Two monkeys passively viewed images of faces, clip-art objects, and computer-generated 'greebles' during broadband recordings from the upper bank superior temporal sulcus (STS; N=13 sessions). For all stimulus-responsive single units, trials were grouped according to the stimulus category presented and spiking was compared to the phase of the frequency components of the local field potential on that trial. For the majority of these cells (N=15), the phase at which firing occurred differed across stimulus categories. The category-selective phase differences were most common in two frequency bands: below 20Hz and in the gamma range (60-80Hz). The phase differences were not sustained throughout the image presentation, but rather were limited to roughly the first 200ms following stimulus onset, with no difference in the time course across frequencies.
These results suggest that the visual category displayed can be extracted from the oscillatory phase when firing occurs. This holds not only for primary cortical areas known for their precise spike timing, but also for cells in association cortex, such as the upper-bank of the STS. Unlike previous studies, we found evidence of phase coding in the gamma frequency range, suggesting that there may be a regional specificity to the coding strategies used. The superior temporal sulcus receives highly-processed signals from multiple modalities, via projections from widespread cortical areas. As such, cells in STS may be less strictly driven by any given sensory input than are cells in early sensory cortical areas. Timing with respect to an internal gamma 'clock' may be one means by which such association areas maintain precise codes, as has been demonstrated previously for other cortical association areas such as the hippocampus (e.g., Buzsaki & Chrobak 1995). The phase coding observed in STS may indicate one role for intrinsic rhythms in the coding of extrinsic - or stimulus-driven - inputs.},
web_url = {http://www.frontiersin.org/10.3389/conf.neuro.06.2009.03.170/event_abstract},
event_name = {Computational and Systems Neuroscience Meeting (COSYNE 2009)},
event_place = {Salt Lake City, UT, USA},
state = {published},
DOI = {10.3389/conf.neuro.06.2009.03.170},
author = {Hoffman K{kari}{Department Physiology of Cognitive Processes}, Turesson H{hjalmar}{Department Physiology of Cognitive Processes}, Ghazanfar AA{asifg}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6177,
title = {SANDBOX, an interactive fMRI data visualization toolbox},
year = {2009},
month = {3},
volume = {2009},
web_url = {http://www2.mrc-lmb.cam.ac.uk/groups/srw/cns/},
event_name = {21st Cambridge Neuroscience Seminar: New Approaches in Neuroscience (CNS 2009)},
event_place = {Cambridge, UK},
state = {published},
author = {Stoewer S{stoewer}{Department Physiology of Cognitive Processes}, Duncan J, Bartels A{abartels}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Sigala N{natasha}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6107,
title = {Evaluating auditory network connectivity with combined microstimulation and functional imaging in the monkey},
year = {2009},
month = {2},
number = {1111},
abstract = {A high-level auditory-cortical region was recently identified with functional magnetic resonance imaging (fMRI) in rhesus monkeys. This brain region shows a close functional correspondence to the so called human-voice region. Both human and monkey ìvoice” regions lie anterior and superior on the temporal lobe and appear to be exquisitely sensitive to certain vocal components in species-specific vocalizations that help to identify other conspecific members of the species. To clarify the in-vivo functional connectivity of the rhesus monkey voice region along with its putative auditory cortical network we used microstimulation in combination with high-resolution fMRI. First we functionally localized the voice region with blood-oxygen-level-dependent (BOLD) fMRI, as previously described. Then we microstimulated this region with glass-coated iridium microelectrodes, using biphasic, cathode leading, 250 to 500 ?A pulses of 200 ?s duration. We used the fMRI BOLD response to evaluate the anterograde targets of the microstimulation site. Microstimulation of the voice region, which lies on the rostral superior-temporal plane (rSTP), elicited a BOLD response from hierarchically earlier auditory areas (feed-back), and the surrounding superior temporal plane (STP), gyrus (STG) and sulcus (STS) of the ipsilateral hemisphere. We next microstimulated an upper-bank STS region that was the target of the voice region. The STS microstimulation seemed to show more robust medial and orbital prefrontal cortex activity in comparison to microstimulation of the voice region on the STP. We are currently comparing these results to those obtained from microstimulating the earlier stages of the auditory cortical pathway and aim to compare our functional connectivity results to anatomical tractography from the analysis of retrograde and anterograde tracers placed in some of the microstimulated regions.},
web_url = {http://www.aro.org/archives/2009/2009_1111_e15f0394.html},
event_name = {32nd Annual Midwinter Meeting of the Association for Research in Otolaryngology (ARO 2009)},
event_place = {Baltimore, MD, USA},
state = {published},
author = {Petkov CI{chrisp}, Kikuchi Y, Augath M{mark}{Department Physiology of Cognitive Processes}, Mishkin M, Rauschecker J and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6142,
title = {Colour, motion and natural vision in the human brain},
year = {2009},
month = {12},
day = {9},
web_url = {http://www.neuroscience-berlin.de/bbd/bbd-archive/article/bbd-program-locations-2009/},
event_name = {Berlin Brain Days},
event_place = {Berlin, Germany},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6141,
title = {The Neurobiology of Love},
year = {2009},
month = {9},
day = {24},
web_url = {http://www.esf.org/activities/exploratory-workshops/humanities-sch/workshops-detail.html?ew=8172},
event_name = {ESF Exploratory Workshop on Neuroesthetics: Where Art and the Brain Collide},
event_place = {Milano, Italy},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6140,
title = {An Introduction to the Visual System},
year = {2009},
month = {9},
day = {11},
event_name = {Lectures on fMRI - European Society for Magnetic Resonance in Medicine and Biology},
event_place = {Tübingen, Germany},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ Logothetis2009_3,
title = {Electrical Microstimulation & fMRI},
journal = {Frontiers in Behavioral Neuroscience},
year = {2009},
month = {9},
volume = {Conference Abstract: 41st European Brain and Behaviour Society Meeting},
abstract = {Electrical stimulation (ES) during fMRI (esfMRI) could provide a unique opportunity to visualize the networks underlying electrostimulation-induced behaviors, to map neuromodulatory systems, or to develop electrotherapy and neural prosthetic devices. Last but not least, esfMRI can offer important insights into the functional neurovascular coupling. In my talk, I shall discuss findings from recent and on-going work on signal propagation during electrical stimulation, as well as our first studies on network plasticity.},
web_url = {http://www.frontiersin.org/10.3389/conf.neuro.08.2009.09.005/event_abstract},
event_name = {41st European Brain and Behaviour Society Meeting},
event_place = {Rhodos, Greece},
state = {published},
DOI = {10.3389/conf.neuro.08.2009.09.005},
author = {Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6173,
title = {Determining neurochemicals from the non-human primate brain by using capillary hydrophilic interaction chromatography-mass spectrometry},
year = {2009},
month = {8},
day = {31},
web_url = {http://www.imsc-bremen-2009.de/},
event_name = {18th International Mass Spectometry Conference (IMSC 2009)},
event_place = {Bremen, Germany},
state = {published},
author = {Zhang XZ{xiaozhe}{Department Physiology of Cognitive Processes}, Rauch A{arauch}{Department Physiology of Cognitive Processes}, Anwesha  B, Li J{juan}{Department Physiology of Cognitive Processes}, Rainer G{gregor} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6042,
title = {Unusual Calcium Sensitivity of Aminobis(methylenephosphonate)-Containing MRI Contrast Agents},
year = {2009},
month = {8},
day = {25},
web_url = {http://www.chemistry-conferences.com/2009/08/23%20-%2027%20Conference%20on%20f-Elements%20%28Cologne%20-%20DE%29.htm},
event_name = {7th International Conference on f-Elements},
event_place = {Köln, Germany},
state = {published},
author = {Angelovski G{goran}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6181,
title = {Dependence of a visual categorisation task on acetylcholine},
journal = {Perception},
year = {2009},
month = {8},
volume = {38},
number = {ECVP Abstract Supplement},
pages = {108},
abstract = {The nervous system is adaptive, so that its neuronal properties can be modified by learning to respond to new categories of stimuli. This is a crucial function of the nervous system not only in children but also in adults and its malfunction can lead to a severely disabling mental disease known as Alzheimer's or senile dementia. Acetylcholine (ACh) is one of the modulators implicated in the brain's adaptive behaviour. Indeed ACh plays an important role in many cognitive functions, including attention (Sarter and Bruno, 2000 Neuroscience 95 933 - 952; Furey et al, 2008 Neuropsychopharmacology 33 913 - 923; Herrero et al, 2008 Nature 454 1110 - 1114), cue detection (Parikh and Sarter, 2008 Annals of the New York Academy of Sciences 1129 225 - 235), learning (Sarter et al, 2003 Neurobiology of Learning & Memory 80 245 - 256), short term-memory (Miller and Desimone, 1993 Neuroreport 4 81 - 84; Thomas et al, 1999 Neuropsychologia 46 2476 - 2484), and long-term memory retrieval (Sarter et al, 2003 Neurobiology of Learning & Memory 80 245 - 256; Rosier et al, 1999 European Journal of Neuroscience 11 3701 - 3714), as well as in Alzheimer's disease. We have examined the effects of scopolamine--an antagonist of muscarinic ACh receptors--on object recognition in macaques. The animal was taught a categorization task, ie to classify stimuli to categories by appropriate behavioural responses. The paradigm involved a fixation task during which an image that belonged to one of the categories was presented. The macaque used levers to categorize the stimulus. Performance of this task was disrupted following injections of scopolamine. When presented with stimuli that belonged to one of these categories but had not been seen before, scopolamine significantly impaired performance in the categorization task. The monkey was still able to carry out the task with a set of familiar stimuli, ie stimuli that it had previously categorized successfully. Performance deteriorated as the stimulus became less salient by increasing the level of visual noise. Scopolamine, however, had no significant or long-lasting effect on performance with familiar stimuli at the different noise levels. In our attempt to localize the effects of ACh we used an analogue of scopolamine that cannot cross the blood brain barrier. The analogue (butyl scopolamine) mimicked the peripheral actions of scopolamine but caused no cognitive deficit. The cognitive changes, therefore, reflect ACh's effect in the brain. The exact site of the effect has not yet been established but is likely to depend on forebrain mechanisms.},
web_url = {http://www.perceptionweb.com/abstract.cgi?id=v090996},
event_name = {32nd European Conference of Visual Perception},
event_place = {Regensburg, Germany},
state = {published},
author = {Aggelopoulos NC{aggelopoulos}{Department Physiology of Cognitive Processes}, Liebe S{sliebe}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Conference{ Logothetis2009_2,
title = {In vivo connectivity: MRI, paramagnetic tracers and electrical stimulation},
journal = {Perception},
year = {2009},
month = {8},
volume = {38},
number = {ECVP Abstract Supplement},
pages = {115},
abstract = {Neuroanatomical cortico-cortical and cortico-subcortical connections have been examined mainly by means of degeneration methods and anterograde and retrograde tracer techniques. Although such studies have demonstrated the value of the information gained from the investigation of the topographic connections between different brain areas, they do require fixed, processed tissue for data analysis and therefore cannot be applied to animals participating in longitudinal studies. Capacities such as plasticity and learning are indeed best studied with non-destructive techniques that can be applied repeatedly and, ideally, combined with neuroimaging or electrophysiology studies. The recent development of MR-visible tracers that can be infused into a specific brain region and are transported anterogradely transsynaptically is one such technique. Simultaneous electrical stimulation (ES) and fMRI (esfMRI) is another. In fact, esfMRI offers a unique opportunity not only to study connectivity, but also to visualize networks underlying electrostimulation-induced behaviors, to map the neuromodulatory systems, or to develop electrotherapy and neural prosthetic devices. In my talk I'll present new data on MR-visible tracers and esfMRI that show the capacity of these methods for the study of connectivity, of cortical microcircuits, and of cortical network reorganization induced by long term potentiation of synapses in subcortical structures, eg in hippocampus.},
web_url = {http://www.perceptionweb.com/abstract.cgi?id=v090743},
event_name = {32nd European Conference on Visual Perception},
event_place = {Regensburg, Germany},
state = {published},
author = {Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ ViswanathanF2009,
title = {Neurometabolic coupling varies with cortical lamina},
journal = {Perception},
year = {2009},
month = {8},
volume = {38},
number = {ECVP Abstract Supplement},
pages = {114},
abstract = {The blood-oxygen-level-dependent (BOLD) signal in functional magnetic resonance imaging (fMRI) is a hemodynamic measurement, which is used to make implications about neural processing. In cerebral cortex, BOLD responses to sensory stimuli are generally averaged across layers. There are clear anatomical and functional differences in laminar cortical organization which imply corresponding variation of BOLD responses. This has been reported in previous visual and somatosensory investigations, but without concurrent measurements of co-localized neural activity. We have modified a multichannel electrode to provide simultaneous measurements of tissue oxygenation and neural activity in different layers of primary visual cortex. We find laminar differences in tissue oxygen response amplitude. In the middle cortical layers, these differences are independent of local variations in neural activation. Our results suggest that neurometabolic coupling differs across cortical lamina.},
web_url = {http://www.perceptionweb.com/abstract.cgi?id=v090874},
event_name = {32nd European Conference on Visual Perception},
event_place = {Regensburg, Germany},
state = {published},
author = {Viswanathan A{ahalya}{Department Physiology of Cognitive Processes} and Freeman RD}
}

@Conference{ Logothetis2009,
title = {Neurovascular coupling: insights from physiology, neuropharmacology and electrical microstimulation},
journal = {Perception},
year = {2009},
month = {8},
volume = {38},
number = {ECVP Abstract Supplement},
pages = {114},
abstract = {In my talk I shall describe our current understanding of the neurophysiological and hemodynamic signals, and of the functional neurovascular coupling in the anesthetized and alert behaving monkey. The neurovascular coupling was studied by means of physiological and fMRI experiments, during neuropharmacological blocking of pyramidal cell activity, and with combined electrical microstimulation and fMRI (esfMRI).},
web_url = {http://www.perceptionweb.com/abstract.cgi?id=v090169},
event_name = {32nd European Conference on Visual Perception},
event_place = {Regensburg, Germany},
state = {published},
author = {Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ 5971,
title = {Die Neurobiologie der Liebe},
year = {2009},
month = {7},
day = {5},
web_url = {http://www.pmu.ac.at/de/1896.htm},
event_name = {Neurobiologie der Psychotherapie, Beziehung und Komplexität},
event_place = {Salzburg, Austria},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ 5962,
title = {Visual influences on voice-selective neurons in the anterior
superior-temporal plane},
year = {2009},
month = {6},
day = {30},
volume = {10},
number = {539},
abstract = {For social interaction and survival primates rely heavily on vocal and facial communication signals from their conspecifics. To date many studies have evaluated the unisensory representations of either vocal or facial information in regions thought to be “voice� or “face� selective. Other studies have directly evaluated the multisensory interactions of voices and faces but have focused on posterior auditory regions closer to the primary auditory cortex. This work investigates multisensory interactions at the neuronal level in an auditory region in the anterior superior temporal plane, which contains one of the important regions for processing “voice�-related information.
Extracellular recordings were obtained from the auditory cortex of macaque monkeys, targeting an anterior “voice� region that we have previously described with functional magnetic resonance imaging (fMRI). For stimulation we used movies of vocalizing monkeys and humans which we matched in their low-level auditory and visual features. These dynamic face and voice stimuli allowed us to evaluate how neurons responded to auditory, visual or audio-visual components of the stimuli. Our experiments also contained control conditions consisting of several mismatched audiovisual stimuli combinations, such as 1) a voice matched to a face from a different species, 2) adding a temporal delay in the visual component of the stimulus, or 3) using an acoustically manipulated voice with the original facial stimulus.
Our neuronal recordings identified a clustered population of voice-selective sites in the anterior superior temporal plane, ~5 mm anterior to field RT. A significant visual influence of the dynamic faces on the corresponding (“matched�) vocalizations was observed in both the local-field potential (LFP) and the spiking activity (analog multiunit activity, AMUA): 38% of the sites showed audiovisual interactions in the LFP signals, and 60% in the AMUA. In addition, the multisensory influence was significantly stronger for the matching voice and face stimuli than to any of the incongruent (“mismatched�) control conditions, confirming the specificity of the cross-sensory influence on the neuronal activity.
Our results provide evidence for visual influences in what has been characterized as an auditory ‘voice’ area. This visual modulation was specific for behaviorally relevant voice-face associations and demonstrates that the processing of voice related information in higher auditory regions can be influenced by multisensory input.},
web_url = {http://imrf.mcmaster.ca/IMRF/ocs/index.php/meetings/2009/paper/view/539},
event_name = {10th International Multisensory Research Forum (IMRF 2009)},
event_place = {New York City, USA},
state = {published},
author = {Perrodin C{cperrodin}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Petkov C{chrisp}}
}

@Conference{ 5970,
title = {The neurobiology of love},
year = {2009},
month = {6},
day = {23},
event_name = {19th World Congress for Sexual Health},
event_place = {Goteborg, Sweden},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ 5969,
title = {Colour, motion and natural vision in the human brain},
year = {2009},
month = {5},
day = {20},
event_name = {Colloques des Neurosciences - Centre Hospitalier Universitaire Vaudois (CHUV)},
event_place = {Lausanne, Switzerland},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ Aggelopoulos2009,
title = {From sensation to perception},
year = {2009},
month = {5},
day = {14},
event_name = {Department of Physiology - University of Ioannina},
event_place = {Ioannina, Greece},
state = {published},
author = {Aggelopoulos N{aggelopoulos}{Department Physiology of Cognitive Processes}}
}

@Conference{ 6180,
title = {Dependence of a cognitive task on acetylcholine},
year = {2009},
month = {5},
abstract = {Information about a stimulus is transmitted within the nervous system by the electrical discharges of neurons. Several different encoding methods have been proposed including a rate‐code, synchrony code and other temporal codes. We have applied information theory to describe the contribution of the different encoding systems in object recognition.
The nervous system not only transmits information but is adaptive so that its neuronal properties can be modified by learning to respond to new categories of stimuli. This is a crucial function of the nervous system not only in children but also in adults and its malfunction can lead to a severely disabling mental disease known as Alzheimer’s or senile dementia.
Acetylcholine is thought to be a chemical transmitter implicated in learning, attention and in Alzheimer’s disease.
In a recent experiment, a macaque monkey was taught a categorization task, in which appropriate behavioral responses assigned stimuli presented on a computer screen to different categories. Performance was disrupted following injections of scopolamine, an antagonist of
muscarinic acetylcholine receptors. When presented with stimuli that belonged to one of these categories but had not been seen before, scopolamine significantly impaired performance in the categorization task. The monkey was still able to carry out the task with a set of familiar stimuli, ie. stimuli that it had previously categorized successfully.
The site of the effect has not been established but it is likely to depend on forebrain mechanisms. An analogue of scopolamine that cannot cross the blood brain barrier mimicked the peripheral actions of scopolamine but caused no cognitive deficit.},
file_url = {/fileadmin/user_upload/files/publications/AIT-Conference-2009-Aggelopoulos_6180[0].pdf},
event_name = {Data Mining in Biomedicine Conference at the Athens Institute of Technology (DMINBIO-09)},
event_place = {Athens, Greece},
state = {published},
author = {Aggelopoulos NC{aggelopoulos}{Department Physiology of Cognitive Processes}, Liebe S{sliebe}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Conference{ 5877,
title = {Gd-DO3A-Ser-Derived Bioresponsive Contrast Agents},
year = {2009},
month = {4},
day = {27},
event_name = {CMST Action D38: Metal-Based Systems for Molecular Imaging Applications, Polatom},
event_place = {Warsaw, Poland},
state = {published},
author = {Dhingra K{kirti}{Department Physiology of Cognitive Processes}}
}

@Conference{ 5768,
title = {The neurobiology of love},
year = {2009},
month = {2},
day = {9},
web_url = {http://www.carls.keio.ac.jp/english/2009/02/the-international-symposium-emotional-animals-sensible-humans-is-held-on-8-9th-february-2009.html},
event_name = {Centre for Advanced Research on Logic and Sensibility (CARLS) Symposium “"Emotional Animals, Sensible Humans”" - Keio University},
event_place = {Tokyo, Japan},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Article{ 5833,
title = {Decoding a bistable percept with integrated time–frequency representation of single-trial local field potential},
journal = {Journal of Neural Engineering},
year = {2008},
month = {12},
volume = {5},
number = {4},
pages = {433-442},
abstract = {Bistable perception emerges when a stimulus under continuous view is perceived as the alternation of two mutually exclusive states. Such a stimulus provides a unique opportunity for understanding the neural basis of visual perception because it dissociates the perception from the visual input. In this paper we analyze the dynamic activity of local field potential (LFP), simultaneously collected from multiple channels in the middle temporal (MT) visual cortex of a macaque monkey, for decoding its bistable structure-from-motion (SFM) perception. Based on the observation that the discriminative information of neuronal population activity evolves and accumulates over time, we propose to select features from the integrated time–frequency representation of LFP using a relaxation (RELAX) algorithm and a sequential forward selection (SFS) algorithm with maximizing the Mahalanobis distance as the criterion function. The integrated-spectrogram based feature selection is much more robust and can achieve significantly better features than the instantaneous-spectrogram based feature selection. We exploit the support vector machines (SVM) classifier and the linear discriminant analysis (LDA) classifier based on the selected features to decode the reported perception on a single trial basis. Our results demonstrate the excellent performance of the integrated-spectrogram based feature selection and suggest that the features in the gamma frequency band (30–100 Hz) of LFP within specific temporal windows carry the most discriminative information for decoding bistable perception. The proposed integrated-spectrogram based feature selection approach may have potential for a myriad of applications involving multivariable time series such as brain–computer interfaces (BCI).},
web_url = {http://www.iop.org/EJ/article/1741-2552/5/4/008/jne8_4_008.pdf},
state = {published},
DOI = {10.1088/1741-2560/5/4/008},
author = {Wang Z, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Liang H}
}

@Article{ 5832,
title = {Encoding of Naturalistic Stimuli by Local Field Potential Spectra in Networks of Excitatory and Inhibitory Neurons},
journal = {PLOS Computational Biology},
year = {2008},
month = {12},
volume = {4},
number = {12},
pages = {1-20},
abstract = {Recordings of local field potentials (LFPs) reveal that the sensory cortex displays rhythmic activity and fluctuations over a wide range of frequencies and amplitudes. Yet, the role of this kind of activity in encoding sensory information remains largely unknown. To understand the rules of translation between the structure of sensory stimuli and the fluctuations of cortical responses, we simulated a sparsely connected network of excitatory and inhibitory neurons modeling a local cortical population, and we determined how the LFPs generated by the network encode information about input stimuli. We first considered simple static and periodic stimuli and then naturalistic input stimuli based on electrophysiological recordings from the thalamus of anesthetized monkeys watching natural movie scenes. We found that the simulated network produced stimulus-related LFP changes that were in striking agreement with the LFPs obtained from the primary visual cortex. Moreover, our results demonstrate that the network encoded static input spike rates into gamma-range oscillations generated by inhibitory–excitatory neural interactions and encoded slow dynamic features of the input into slow LFP fluctuations mediated by stimulus–neural interactions. The model cortical network processed dynamic stimuli with naturalistic temporal structure by using low and high response frequencies as independent communication channels, again in agreement with recent reports from visual cortex responses to naturalistic movies. One potential function of this frequency decomposition into independent information channels operated by the cortical network may be that of enhancing the capacity of the cortical column to encode our complex sensory environment.},
web_url = {http://www.ploscompbiol.org/article/fetchObjectAttachment.action?uri=info%3Adoi%2F10.1371%2Fjournal.pcbi.1000239&representation=PDF},
state = {published},
DOI = {10.1371/journal.pcbi.1000239},
EPUB = {e1000239},
author = {Mazzoni A, Panzeri S{stefano}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Brunel N}
}

@Article{ 5614,
title = {Feature selectivity of the gamma-band of the local field potential in primate primary visual cortex},
journal = {Frontiers in Neuroscience},
year = {2008},
month = {12},
volume = {2},
number = {2},
pages = {199-207},
abstract = {Extra-cellular voltage fluctuations (local field potentials; LFPs) reflecting neural mass action are ubiquitous across species and brain regions. Numerous studies have characterized the properties of LFP signals in the cortex to study sensory and motor computations as well as cognitive processes like attention, perception and memory. In addition, its extracranial counterpart – the electroencelphalogram (EEG) – is widely used in clinical applications. However, the link between LFP signals and the underlying activity of local populations of neurons remains largely elusive. Here, we review recent work elucidating the relationship between spiking activity of local neural populations and LFP signals. We focus on oscillations in the gamma-band (30-90Hz) of the local field potential in the primary visual cortex (V1) of the macaque that dominate during visual stimulation. Given that in area V1 much is known about the properties of single neurons and the cortical architecture, it provides an excellent opportunity to
study the mechanisms underlying the generation of the local field potential.},
web_url = {http://frontiersin.org/neuroscience/paper/10.3389/neuro.01/037.2008/pdf/},
state = {published},
DOI = {10.3389/neuro.01.037.2008},
author = {Berens P{berens}{Research Group Computational Vision and Neuroscience}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Ecker AS{aecker}{Research Group Computational Vision and Neuroscience}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Tolias AS{atolias}{Department Physiology of Cognitive Processes}}
}

@Article{ 5483,
title = {Fine-Scale Spatial Organization of Face and Object Selectivity in the Temporal Lobe: Do Functional Magnetic Resonance Imaging, Optical Imaging, and Electrophysiology Agree?},
journal = {Journal of Neuroscience},
year = {2008},
month = {11},
volume = {28},
number = {46},
pages = {11796-11801},
abstract = {The spatial organization of the brain‘s object and face representations in the temporal lobe is critical for understanding high-level vision and cognition but is poorly understood. Recently, exciting progress has been made using advanced imaging and physiology methods in humans and nonhuman primates, and the combination of such methods may be particularly powerful. Studies applying these methods help us to understand how neuronal activity, optical imaging, and functional magnetic resonance imaging signals are related within the temporal lobe, and to uncover the fine-grained and large-scale spatial organization of object and face representations in the primate brain.},
web_url = {http://www.jneurosci.org/cgi/reprint/28/46/11796},
state = {published},
DOI = {10.1523/JNEUROSCI.3799-08.2008},
author = {Op De Beeck HP, Carlo JJD, Goense J{jozien}{Department Physiology of Cognitive Processes}, Grill-Spector K, Papanastassiou A, Tanifuji M and Tsao DY}
}

@Article{ 4956,
title = {The Influence of Moderate Hypercapnia on Neural Activity in the Anesthetized Nonhuman Primate},
journal = {Cerebral Cortex},
year = {2008},
month = {11},
volume = {18},
number = {11},
pages = {2666-2673},
abstract = {Hypercapnia is often used as vasodilatory challenge in clinical applications and
basic research. In functional magnetic resonance imaging (fMRI), elevated CO2
is applied to derive stimulus-induced changes in the cerebral rate of oxygen
consumption (CMRO2) by measuring cerebral blood flow (CBF) and bloodoxygenation-
level-dependent (BOLD) signal. Such methods, however, assume
that hypercapnia has no direct effect on CMRO2. In this study, we used
combined intracortical recordings and fMRI in the visual cortex of anesthetized
macaque monkeys to show that spontaneous neuronal activity is in fact
significantly reduced by moderate hypercapnia. As expected, measurement of
cerebral blood volume using an exogenous contrast agent and of BOLD signal
showed that both are increased during hypercapnia. In contrast to this,
spontaneous fluctuations of local field potentials in the beta and gamma
frequency range as well as multi-unit activity are reduced by ~15% during
inhalation of 6% CO2 (pCO2 = 56 mmHg). A strong tendency toward a reduction
of neuronal activity was also found at CO2 inhalation of 3% (pCO2 = 45 mmHg).
This suggests that CMRO2 might be reduced during hypercapnia and caution
must be exercised when hypercapnia is applied to calibrate the BOLD signal.},
web_url = {http://cercor.oxfordjournals.org/cgi/reprint/bhn023v2},
state = {published},
DOI = {10.1093/cercor/bhn023},
author = {Zappe A-C{aczappe}{Department Physiology of Cognitive Processes}, Uludag K{kuludag}{Department High-Field Magnetic Resonance}, Oeltermann A{axel}, Ugurbil K and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5591,
title = {Mass spectrometry-based neurochemical analysis: perspectives for primate research},
journal = {Expert Review of Proteomics},
year = {2008},
month = {10},
volume = {5},
number = {5},
pages = {641-652},
abstract = {The analysis of neurochemicals from the brain represents a challenge for current analytical techniques due to a variety of factors, such as compositional complexity, limited amounts of sample and endogenous inferences. Advances in mass spectrometry (MS) provide great opportunities for the sensitive measurement of neurochemicals, offering benefits including simple sample preparation, broad capability for analysis of diverse compounds and rich structural information of analytes. Until recently, however, limited numbers of studies have reported on the analysis of small molecular neurochemicals, such as classical neurotransmitters, in part due to the difficulties in separation of polar molecules by using current chromatography techniques with MS-compatible conditions. By contrast, MS has become an indispensable tool for neuropeptide analysis , offering tremendous potential in the discovery of novel signaling peptides and biomarkers. This review covers recent advances in MS-based neurochemical analysis , including a comparison with related detection techniques, chromatographic separation and neuropeptide discovery. Issues relating to in vivo sample collection and sample preparation are discussed. To provide a wider view of the capability of MS in basic neuroscience and clinical research, we discuss MS-based neurochemical analysis conducted in different animal models and humans. We specifically highlight perspectives for the use of MS for brain functional studies and drug discovery in nonhuman primates.},
web_url = {http://www.expert-reviews.com/doi/pdf/10.1586/14789450.5.5.641},
state = {published},
DOI = {10.1586/14789450.5.5.641},
author = {Zhang X{xiaozhe}{Department Physiology of Cognitive Processes}, Rauch A{arauch}{Department Physiology of Cognitive Processes}, Xiao H{hbxiao}, Rainer G{gregor} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ PanzeriMC2008,
title = {Sampling bias},
journal = {Scholarpedia},
year = {2008},
month = {10},
volume = {3},
number = {9},
pages = {4258},
abstract = {Sampling bias means that the samples of a stochastic variable that are collected to determine its distribution are selected incorrectly and do not represent the true distribution because of non-random reasons. Let us consider a specific example: we might want to predict the outcome of a presidential election by means of an opinion poll. Asking 1000 voters about their voting intentions can give a pretty accurate prediction of the likely winner, but only if our sample of 1000 voters is 'representative' of the electorate as a whole (i.e. unbiased). If we only poll the opinion of, 1000 white middle class college students, then the views of many important parts of the electorate as a whole (ethnic minorities, elderly people, blue-collar workers) are likely to be underrepresented in the sample, and our ability to predict the outcome of the election from that sample is reduced.

In an unbiased sample, differences between the samples taken from a random variable and its true distribution, or differences between the samples of units from a population and the entire population they represent, should result only from chance. If their differences are not only due to chance, then there is a sampling bias. Sampling bias often arises because certain values of the variable are systematically under-represented or over-represented with respect to the true distribution of the variable (like in our opinion poll example above). Because of its consistent nature, sampling bias leads to a systematic distortion of the estimate of the sampled probability distribution. This distortion cannot be eliminated by increasing the number of data samples and must be corrected for by means of appropriate techniques, some of which are discussed below. In other words, polling an additional 1000 white college students will not improve the predictive power of our opinion poll, but polling 1000 individuals chosen at random from the electoral roll would. Obviously, a biased sample may cause problems in the measure of probability functionals (e.g., the variance or the entropy of the distribution), since any statistics computed from that sample has the potential to be consistently erroneous.},
web_url = {http://www.scholarpedia.org/article/Sampling_bias},
state = {published},
DOI = {10.4249/scholarpedia.4258},
author = {Panzeri S{stefano}, Magri C{cmagri}{Department Physiology of Cognitive Processes} and Carraro L}
}

@Article{ 4901,
title = {The microvascular system of the striate and extrastriate visual cortex of the macaque},
journal = {Cerebral Cortex},
year = {2008},
month = {10},
volume = {18},
number = {10},
pages = {2318-2330},
abstract = {In functional neuroimaging, neurovascular coupling is used to generate maps of hemodynamic changes that are assumed to be surrogates of regional neural activation. The aim of this study was to characterize the microvascular system of the primate cortex as a basis for understanding the constraints imposed on a region's hemodynamic response by the vascular architecture, density, as well as area- and layer-specific variations. In the macaque visual cortex, an array of anatomical techniques has been applied, including corrosion casts, immunohistochemistry, and cytochrome oxidase (COX) staining. Detailed measurements of regional vascular length density, volume fraction, and surface density revealed a similar vascularization in different visual areas. Whereas the lower cortical layers showed a positive correlation between the vascular and cell density, this relationship was very weak in the upper layers. Synapse density values taken from the literature also displayed a very moderate correlation with the vascular density. However, the vascular density was strongly correlated with the steady-state metabolic demand as measured by COX activity. This observation suggests that although the number of neurons and synapses determines an upper bound on an area's integrative capacity, its vascularization reflects the neural activity of those subpopulations that represent a “default” mode of brain steady state.},
web_url = {http://cercor.oxfordjournals.org/cgi/reprint/18/10/2318},
state = {published},
DOI = {10.1093/cercor/bhm259},
author = {Weber B{bweber}, Keller AL{akeller}{Department Physiology of Cognitive Processes}, Reichold J{reichold}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 4877,
title = {Comparison of Pattern Recognition Methods in Classifying High-resolution BOLD Signals Obtained at High Magnetic Field in Monkeys},
journal = {Magnetic Resonance Imaging},
year = {2008},
month = {9},
volume = {26},
number = {7},
pages = {1007-1014},
abstract = {Pattern recognition methods have shown that functional magnetic resonance imaging (fMRI) data can reveal significant information about brain activity. For example, in the debate of how object categories are represented in the brain, multivariate analysis has been used to provide evidence of a distributed encoding scheme [Science 293:5539 (2001) 2425–2430]. Many follow-up studies have employed different methods to analyze human fMRI data with varying degrees of success [Nature reviews 7:7 (2006) 523–534]. In this study, we compare four popular pattern recognition methods: correlation analysis, support-vector machines (SVM), linear discriminant analysis (LDA) and Gaussian naïve Bayes (GNB), using data collected at high field (7 Tesla) with higher resolution than usual fMRI studies. We investigate prediction performance on single trials and for averages across varying numbers of stimulus presentations. The performance of the various algorithms depends on the nature of the brain activity being categorized: for
several tasks, many of the methods work well, whereas for others, no method performs above chance level. An important factor in overall classification performance is careful preprocessing of the data, including dimensionality reduction, voxel selection and outlier elimination.},
file_url = {/fileadmin/user_upload/files/publications/sdarticle_4877[0].pdf},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6T9D-4T5BWJY-5-7&amp;_cdi=5112&amp;_user=29041&amp;_orig=browse&amp;_coverDate=09%2F30%2F2008&amp;_sk=999739992&amp;view=c&amp;wchp=dGLbVzz-zSkWb&amp;md5=25e9},
state = {published},
DOI = {http://dx.doi.org/10.1016/j.mri.2008.02.016},
author = {Ku S-P{shihpi}{Department Physiology of Cognitive Processes}, Gretton A{arthur}{Department Empirical Inference}, Macke J{jakob}{Department Empirical Inference} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 4918,
title = {Direct measurement of oxygen extraction with fMRI using 6% CO2 inhalation},
journal = {Magnetic Resonance Imaging},
year = {2008},
month = {9},
volume = {26},
number = {7},
pages = {961-967},
abstract = {The blood oxygenation level-dependent (BOLD) signal is an indirect
hemodynamic signal which is sensitive to cerebral blood flow (CBF), cerebral
blood volume (CBV) and cerebral metabolic rate of oxygen (CMRO2). Therefore,
the BOLD signal amplitude and dynamics cannot be interpreted unambiguously
without additional physiological measurements and, thus, there remains a need
for a functional magnetic resonance imaging (fMRI) signal which is more closely
related to the underlying neuronal activity. In this study, we measured cerebral
blood flow with continuous arterial spin labeling, cerebral blood volume with an
exogenous contrast agent and BOLD combined with intracortical
electrophysiological recording in primary visual cortex of the anesthetized
monkey. During inhalation of 6% CO2, it was observed that CBF and CBV are not
further increased by a visual stimulus, although baseline CBF for 6% CO2 is
below the maximal value of CBF. In contrast, the electrophysiological response
to the stimulation was found to be preserved during hypercapnia. As a
consequence, the simultaneously measured BOLD signal responds negatively to
a visual stimulation for 6% CO2 inhalation in the same voxels responding
positively during normocapnia. These observations suggest that the fMRI
response to a sensory stimulus for 6% CO2 inhalation occurs in the absence of a
hemodynamic response, and it therefore directly reflects the oxygen extraction
into the tissue.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T9D-4SDNK82-1-1&_cdi=5112&_user=29041&_orig=search&_coverDate=09%2F30%2F2008&_sk=999739992&view=c&wchp=dGLzVtb-zSkzS&md5=a68ebcb9c19df1431bbf6ced51eeb30a&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.mri.2008.02.005},
author = {Zappe A-C{aczappe}{Department Physiology of Cognitive Processes}, Uludag K{kuludag}{Department High-Field Magnetic Resonance} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 4909,
title = {Electric stimulation fMRI of the perforant pathway to the rat hippocampus},
journal = {Magnetic Resonance Imaging},
year = {2008},
month = {9},
volume = {26},
number = {7},
pages = {978-986},
abstract = {The hippocampal formation is a brain system that is implicated in learning and memory. The major input to the hippocampus arrives from the entorhinal cortex (EC) to the dentate gyrus (DG) through the perforant path. In the present work, we have investigated the functional properties of this connection by concomitantly applying electrophysiological techniques, deep-brain electric microstimulation and functional magnetic resonance imaging in anesthetized rats. We systematically delivered different current intensities at diverse stimulation frequencies to the perforant path while recording electrophysiological and blood-oxygenation-level-dependent (BOLD) signals. We observed a linear relationship between the current intensity used to stimulate the hippocampal formation and the amplitude and extension of the induced BOLD response. In addition, we found a frequency-dependent spatial pattern of activation. With stimulation protocols and train frequencies used for kindling, the activity strongly spreads ipsilaterall
y through the hippocampus, DG, subiculum and EC.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T9D-4SH1HXR-B-5&_cdi=5112&_user=29041&_orig=search&_coverDate=09%2F30%2F2008&_sk=999739992&view=c&wchp=dGLzVtb-zSkWz&md5=e7e95446b785f4dd0f51d9b02acb372d&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.mri.2008.02.018},
author = {Canals S{canals}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5282,
title = {fMRI and its interpretations: an illustration on directional selectivity in area V5/MT},
journal = {Trends in Neurosciences},
year = {2008},
month = {9},
volume = {31},
number = {9},
pages = {444-453},
abstract = {fMRI is a tool to study brain function noninvasively that can reliably identify sites of neural involvement for a given task. However, to what extent can fMRI signals be related to measures obtained in electrophysiology? Can the blood-oxygen-level-dependent signal be interpreted as spatially pooled spiking activity? Here we combine knowledge from neurovascular coupling, functional imaging and neurophysiology to discuss whether fMRI has succeeded in demonstrating one of the most established functional properties in the visual brain, namely directional selectivity in the motion-processing region V5/MT+. We also discuss differences of fMRI and electrophysiology in their sensitivity to distinct physiological processes. We conclude that fMRI constitutes a complement, not a poor-resolution substitute, to invasive techniques, and that it deserves interpretations that acknowledge its stand as a separate signal.},
web_url = {http://www.sciencedirect.com/science/article/pii/S0166223608001628},
state = {published},
DOI = {doi:10.1016/j.tins.2008.06.004},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Moutoussis K{kmoutou}{Department Physiology of Cognitive Processes}}
}

@Article{ 5684,
title = {fMRI measurements of color in macaque and human},
journal = {Journal of Vision},
year = {2008},
month = {9},
volume = {8},
number = {10:6},
pages = {1-19},
abstract = {We have used fMRI to measure responses to chromatic and achromatic contrast in retinotopically defined regions of macaque and human visual cortex. We make four observations. Firstly, the relative amplitudes of responses to color and luminance stimuli in macaque area V1 are similar to those previously observed in human fMRI experiments. Secondly, the dorsal and ventral subdivisions of macaque area V4 respond in a similar way to opponent (L &#8722; M)-cone chromatic contrast suggesting that they are part of a single functional area. Thirdly, we find that macaque area V4, like area V1, responds preferentially to chromatic contrast compared to luminance contrast and the degree of preference is strongly influenced by the temporal frequency of the stimulus. Finally, we observe that while macaque V4d is a region on the dorsal surface of the macaque visual cortex that responds robustly to chromatic stimuli, human chromatic responses to identical stimuli are largely confined to the ventral surface s
uggesting a fundamental difference in the topographical organization of higher visual areas between humans and macaques.},
file_url = {/fileadmin/user_upload/files/publications/Wade-2008-jov-8-10-6_5684[0].pdf},
web_url = {http://journalofvision.org/8/10/6/Wade-2008-jov-8-10-6.pdf},
state = {published},
DOI = {10.1167/8.10.6},
author = {Wade A, Augath M{mark}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Wandell B}
}

@Article{ 5836,
title = {On the use of information theory for the analysis of the relationship between neural and imaging signals},
journal = {Magnetic Resonance Imaging},
year = {2008},
month = {9},
volume = {26},
number = {7},
pages = {1015-1025},
abstract = {Functional magnetic resonance imaging (fMRI) is a widely used method for studying the neural basis of cognition and of sensory function. A potential problem in the interpretation of fMRI data is that fMRI measures neural activity only indirectly, as a local change of deoxyhemoglobin concentration due to the metabolic demands of neural function. To build correct sensory and cognitive maps in the human brain, it is thus crucial to understand whether fMRI and neural activity convey the same type of information about external correlates. While a substantial experimental effort has been devoted to the simultaneous recordings of hemodynamic and neural signals, so far, the development of analysis methods that elucidate how neural and hemodynamic signals represent sensory information has received less attention. In this article, we critically review why the analytical framework of information theory, the mathematical theory of communication, is ideally suited to this purpose. We review the principles of information theory and explain how they could be applied to the analysis of fMRI and neural signals. We show that a critical advantage of information theory over more traditional analysis paradigms commonly used in the fMRI literature is that it can elucidate, within a single framework, whether an empirically observed correlation between neural and fMRI signals reflects either a similar stimulus tuning or a common source of variability unrelated to the external stimuli. In addition, information theory determines the extent to which these shared sources of stimulus signal and of variability lead fMRI and neural signals to convey similar information about external correlates. We then illustrate the formalism by applying it to the analysis of the information carried by different bands of the local field potential. We conclude by discussing the current methodological challenges that need to be addressed to make the information-theoretic approach more robustly applicable to the simultaneous recordings of neural and imaging data.},
web_url = {http://www.sciencedirect.com/science?_ob=MiamiImageURL&_cid=271222&_user=29041&_pii=S0730725X08001033&_check=y&_origin=&_coverDate=30-Sep-2008&view=c&wchp=dGLzVlV-zSkzS&md5=82dc9bb12260c28314c5ee009ef6de69/1-s2.0-S0730725X08001033-main.pdf},
state = {published},
DOI = {10.1016/j.mri.2008.02.019},
author = {Panzeri S{stefano}, Magri C{cmagri}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ ThielscherRW2008,
title = {Effects of TMS on visual evoked potentials in a visual suppression task},
journal = {Brain Stimulation},
year = {2008},
month = {7},
volume = {1},
number = {3},
pages = {275-276},
abstract = {Method:

In 3 subjects, VEPs were reliably induced by a small checkerboard stimulus briefly presented in the parafoveal lower right quadrant (Fig. 1B). Subjects S1 and S2 had classical VEP patterns, in S3 the P100 was missing. A random quadrant of the checkerboard was shown at reduced contrast. Subjects had to identify and report it by a button-press. TMS was applied to the left occ. pole (MagVenture MagPro X100; MC-B70 coil). The best TMS timing and coil position were determined in pretests. The timing with the strongest suppression corresponded to the N80 (S1&S2) and the missing P100 (S3), respectively.

We tested 3 conditions: Combined “TMS&visual” stimulation, “Visualonly” and “TMSonly”. An experimental run (∼4min) contained trials of all conditions in a randomized order. 5 TMS intensities were tested, ranging from phosphene threshold to the intensity evoking chance level performance (or maximally 85% of max. stimulator output; Fig.1A). The 5 intensities were tested in separate runs in a randomized order. Using several sessions, ∼120 trials were acquired for each condition at each intensity.

EEG was recorded using a BrainAmp MR plus amplifier (Brain Products, Germany; 32 channels; impedances <5 kOhm) and analyzed using EEGLAB 6.01 (Delorme & Makeig, 2004). Pre-processing involved TMS artifact removal using polynomial interpolation, band-pass filtering (cutoff 0.1 & 50 Hz), baseline correction and eye blink rejection. The mean of the TMSonly trials was subtracted from the mean of the TMS&visual trials to determine the TMS effect on the VEPs. Analysis concentrated on a region-of-interest of 7 electrodes (Fig. 1C).
Result:

In S1 and S2, the P100 increased monotonically for the 3 lower TMS intensities (Fig. 1C&D) and leveled off for the 2 highest intensities, at which visual suppression occurred (Fig. 1A). In S3, the N150 increased for the first 4 intensities, and then decreased. Similar modulations occured for the N150 in S1 and S2 and the “P200” in S3 (data not shown).
Conclusion:

The VEP modulation patterns hint towards a saturation effect taking place when TMS is strong enough to induce robust suppression. Future work involves testing a further subject to confirm the modulation effects, and the systematic variation of the TMS SOA.},
web_url = {http://www.sciencedirect.com/science/article/pii/S1935861X08002696},
state = {published},
DOI = {10.1016/j.brs.2008.06.233},
author = {Thielscher A{thielscher}{Department High-Field Magnetic Resonance}, Reichenbach A{areichen}{Department Human Perception, Cognition and Action}{Department High-Field Magnetic Resonance} and Whittingstall K{kevin}{Department Physiology of Cognitive Processes}}
}

@Article{ 5082,
title = {Smart Magnetic Resonance Imaging Agents that Sense Extracellular Calcium Fluctuations},
journal = {ChemBioChem},
year = {2008},
month = {7},
volume = {9},
number = {11},
pages = {1729-1734},
abstract = {Gd3+ chelates linked to a modified EGTA moiety were prepared in order to
respond to extracellular Ca2+ fluctuations in the brain











Gd3+ chelates linked to a
modified EGTA moiety were prepared in order to respond to extracellular Ca2+
fluctuations in the brain. Upon interaction with Ca2+, they exhibit
high and reversible relaxivity changes in buffered solution or in a model of
the brain extracellular medium. These efficient Ca2+ magnetic
resonance imaging sensors might open new perspectives in functional molecular
imaging.},
web_url = {http://www3.interscience.wiley.com/cgi-bin/fulltext/120695271/PDFSTART},
state = {published},
DOI = {10.1002/cbic.200800165},
author = {Angelovski G{goran}{Department Physiology of Cognitive Processes}, Fouskov{\'a} P, Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, Canals S{canals}, T{\'o}th {\'E} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 4903,
title = {Visual modulation of neurons in auditory cortex},
journal = {Cerebral Cortex},
year = {2008},
month = {7},
volume = {18},
number = {7},
pages = {1560-1574},
abstract = {Our brain integrates the information provided by the different
sensory modalities into a coherent percept, and recent studies
suggest that this process is not restricted to higher association
areas. Here we evaluate the hypothesis that auditory cortical fields
are involved in cross-modal processing by probing individual
neurons for audiovisual interactions. We find that visual stimuli
modulate auditory processing both at the level of field potentials
and single-unit activity and already in primary and secondary
auditory fields. These interactions strongly depend on a stimulus’
efficacy in driving the neurons but occur independently of stimulus
category and for naturalistic as well as artificial stimuli. In addition,
interactions are sensitive to the relative timing of audiovisual
stimuli and are strongest when visual stimuli lead by 20--80 msec.
Exploring the underlying mechanisms, we find that enhancement
correlates with the resetting of slow (~10 Hz) oscillations to
a phase angle of optimal excitability. These results demonstrate
that visual stimuli can modulate the firing of neurons in auditory
cortex in a manner that depends on stimulus efficacy and timing.
These neurons thus meet the criteria for sensory integration and
provide the auditory modality with multisensory contextual information
about co-occurring environmental events.},
file_url = {/fileadmin/user_upload/files/publications/Kayser_CerCor_08_[0].pdf},
web_url = {http://cercor.oxfordjournals.org/cgi/reprint/18/7/1560},
state = {published},
DOI = {10.1093/cercor/bhm187},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Petkov CI{chrisp} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5205,
title = {Comparing the feature selectivity of the gamma-band of the local field potential and the underlying spiking activity in primate visual cortex},
journal = {Frontiers in Systems Neuroscience},
year = {2008},
month = {6},
volume = {2},
number = {2},
pages = {1-11},
abstract = {The local field potential (LFP), comprised of low-frequency extra-cellular voltage fluctuations, has been used extensively to study the mechanisms of brain function. In particular, oscillations in the gamma-band (30–90 Hz) are ubiquitous in the cortex of many species during various cognitive processes. Surprisingly little is known about the underlying biophysical processes generating this signal. Here, we examine the relationship of the local field potential to the activity of localized populations of neurons by simultaneously recording spiking activity and LFP from the primary visual cortex (V1) of awake, behaving macaques. The spatial organization of orientation tuning and ocular dominance in this area provides an excellent opportunity to study this question, because orientation tuning is organized at a scale around one order of magnitude finer than the size of ocular dominance columns. While we find a surprisingly weak correlation between the preferred orientation of multi-unit activity and gamma-band LFP
recorded on the same tetrode, there is a strong correlation between the ocular preferences of both signals. Given the spatial arrangement of orientation tuning and ocular dominance, this leads us to conclude that the gamma-band of the LFP seems to sample an area considerably larger than orientation columns. Rather, its spatial resolution lies at the scale of ocular dominance columns.},
web_url = {http://www.frontiersin.org/systemsneuroscience/paper/10.3389/neuro.06/002.2008/pdf/},
state = {published},
DOI = {10.3389/neuro.06.002.2008},
author = {Berens P{berens}{Research Group Computational Vision and Neuroscience}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Ecker AS{aecker}{Research Group Computational Vision and Neuroscience}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Tolias AS{atolias}{Department Physiology of Cognitive Processes}}
}

@Article{ 5128,
title = {Synthesis and Characterization of a Smart Contrast Agent Sensitive to Calcium},
journal = {Chemical Communications},
year = {2008},
month = {6},
volume = {29},
pages = {3444-3446},
abstract = {A novel first-generation Ca2+ sensitive contrast agent, Gd-DOPTRA has been synthesized and characterized. The agent shows 100% relaxivity enhancement upon addition of Ca2+. The agent is selective and sensitive to Ca2+ also in the presence of Mg2+ and Zn2+. The relaxivity studies carried out in physiological fluids prove the prospects of the agent for in vivo measurements.},
web_url = {http://www.rsc.org/ej/CC/2008/b801975d.pdf},
state = {published},
DOI = {10.1039/b801975d},
author = {Dhingra K{kirti}{Department Physiology of Cognitive Processes}, Maier ME, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Angelovski G{goran}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5737,
title = {What we can do and what we cannot do with fMRI},
journal = {Nature},
year = {2008},
month = {6},
volume = {453},
number = {7197},
pages = {869-878},
abstract = {Functional magnetic resonance imaging (fMRI) is currently the mainstay of neuroimaging in cognitive neuroscience. Advances in scanner technology, image acquisition protocols, experimental design, and analysis methods promise to push forward fMRI from mere cartography to the true study of brain organization. However, fundamental questions concerning the interpretation of fMRI data abound, as the conclusions drawn often ignore the actual limitations of the methodology. Here I give an overview of the current state of fMRI, and draw on neuroimaging and physiological data to present the current understanding of the haemodynamic signals and the constraints they impose on neuroimaging data interpretation.},
file_url = {/fileadmin/user_upload/files/publications/NikosNatureJune2008_[0].pdf},
web_url = {http://www.nature.com/nature/journal/v453/n7197/pdf/nature06976.pdf},
state = {published},
DOI = {10.1038/nature06976},
author = {Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5249,
title = {Low-frequency Local Field Potentials and Spikes in Primary Visual Cortex Convey Independent Visual Information},
journal = {Journal of Neuroscience},
year = {2008},
month = {5},
volume = {28},
number = {22},
pages = {5696-5709},
abstract = {Local field potentials (LFPs) reflect subthreshold integrative processes that complement spike train measures. However, little is yet known about the differences between how LFPs and spikes encode rich naturalistic sensory stimuli. We addressed this question by recording LFPs and spikes from the primary visual cortex of anesthetized macaques while presenting a color movie. We then determined how the power of LFPs and spikes at different frequencies represents the visual features in the movie. We found that the most informative LFP frequency ranges were 1&amp;amp;amp;amp;#8211;8 and 60&amp;amp;amp;amp;#8211;100 Hz. LFPs in the range of 12&amp;amp;amp;amp;#8211;40 Hz carried little information about the stimulus, and may primarily reflect neuromodulatory inputs. Spike power was informative only at frequencies &amp;amp;amp;lt;12 Hz. We further quantified "signal correlations" (correlations in the trial-averaged power response to differen
t stimuli) and "
noise correlatio
ns" (trial-by-tr
ial correlations
in the fluctuations around the average) of LFPs and spikes recorded from the same electrode. We found positive signal correlation between high-gamma LFPs (60&amp;amp;amp;amp;#8211;100 Hz) and spikes, as well as strong positive signal correlation within high-gamma LFPs, suggesting that high-gamma LFPs and spikes are generated within the same network. LFPs &amp;amp;amp;lt;24 Hz shared strong positive noise correlations, indicating that they are influenced by a common source, such as a diffuse neuromodulatory input. LFPs &amp;amp;amp;lt;40 Hz showed very little signal and noise correlations with LFPs &amp;amp;amp;gt;40 Hz and with spikes, suggesting that low-frequency LFPs reflect neural processes that in natural conditions are fully decoupled from those giving rise to spikes and to high-gamma LFPs.},
web_url = {http://www.jneurosci.org/cgi/reprint/28/22/5696},
state = {published},
DOI = {10.1523/JNEUROSCI.0009-08.2008},
author = {Belitski A{belitski}{Department Physiology of Cognitive Processes}, Gretton A{arthur}, Magri C{cmagri}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Montemurro MA, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Article{ 4895,
title = {Morphing rhesus monkey vocalizations},
journal = {Journal of Neuroscience Methods},
year = {2008},
month = {5},
volume = {170},
number = {1},
pages = {45-55},
abstract = {The capability to systematically morph between different types of animal vocalizations will give us insights into how the features of vocal sounds are perceived by listening individuals. Following behavioral study, neurophysiological recordings in nonhuman animals, could reveal how neurons support the perception of communication signals. Signal processing algorithms are now available for creating sophisticated morphs between complex sounds, like human speech. However, most morphing approaches have been applied to harmonic sounds whose frequency components
can be readily identified. We show that auditory morphing can be more generally applied by describing a procedure for using the STRAIGHT
signal processing package to gradually morph between: (1) vocalizations from different macaque monkeys, (2) acoustically dissimilar types of monkey vocalizations, such as a ‘coo’ and a ‘grunt’, and (3) monkey and human vocalizations. We then evaluated the quality of the morphs and obtained classification curves from human listeners who seemed to categorize the monkey vocalizations much like the ones produced by humans. The outlined procedures prepare macaque-monkey vocalizations for neuroethological study and the approach establishes basic principles that will assist in creating suitable morphs of other natural sounds and animal vocalizations.},
file_url = {/fileadmin/user_upload/files/publications/Chakladar%20-%20Morphing%20Monkey%20Vocalizations%20-%20JNMethods%20-%202008_4895[0].pdf},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T04-4RM1KNS-2-S&_cdi=4852&_user=29041&_orig=search&_coverDate=05%2F15%2F2008&_sk=998299998&view=c&wchp=dGLbVlz-zSkWW&md5=996e3edcb35ab972100511d15d95b34a&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.jneumeth.2007.12.023},
author = {Chakladar S{chakladar}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Petkov CI{chrisp}}
}

@Article{ 5482,
title = {Neurophysiology of the BOLD fMRI Signal in Awake Monkeys},
journal = {Current Biology},
year = {2008},
month = {5},
volume = {18},
number = {9},
pages = {631-640},
abstract = {Background

Simultaneous intracortical recordings of neural activity and blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) in primary visual cortex of anesthetized monkeys demonstrated varying degrees of correlation between fMRI signals and the different types of neural activity, such as local field potentials (LFPs), multiple-unit activity (MUA), and single-unit activity (SUA). One important question raised by the aforementioned investigation is whether the reported correlations also apply to alert subjects.
Results

Monkeys were trained to perform a fixation task while stimuli within the receptive field of each recording site were used to elicit neural responses followed by a BOLD response. We show – also in alert behaving monkeys – that although both LFP and MUA make significant contributions to the BOLD response, LFPs are better and more reliable predictors of the BOLD signal. Moreover, when MUA responses adapt but LFP remains unaffected, the BOLD signal remains unaltered.
Conclusions

The persistent coupling of the BOLD signal to the field potential when LFP and MUA have different time evolutions suggests that BOLD is primarily determined by the local processing of inputs in a given cortical area. In the alert animal the largest portion of the BOLD signal‘s variance is explained by an LFP range (20–60 Hz) that is most likely related to neuromodulation. Finally, the similarity of the results in alert and anesthetized subjects indicates that at least in V1 anesthesia is not a confounding factor. This enables the comparison of human fMRI results with a plethora of electrophysiological results obtained in alert or anesthetized animals.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6VRT-4SBYX23-1-J&_cdi=6243&_user=29041&_orig=browse&_coverDate=05%2F06%2F2008&_sk=999819990&view=c&wchp=dGLzVlz-zSkWz&md5=cf054af241b9e9e767c907669da26ced&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.cub.2008.03.054},
author = {Goense JBM{jozien}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 6185,
title = {Presynaptic control of transmission through group II muscle afferents in the midlumbar and sacral segments of the spinal cord is independent of corticospinal control},
journal = {Experimental Brain Research},
year = {2008},
month = {5},
volume = {187},
number = {1},
pages = {61-70},
abstract = {Transmission of information from the terminals group II muscle afferents is subject to potent presynaptic modulation by both segmental group II and cutaneous afferents and by descending monoaminergic systems. Currently it is unknown whether descending corticospinal fibres affect this transmission. Here we have examined whether corticospinal tract activation modulates the size of monosynaptic focal synaptic potentials (FSPs) evoked by group II muscle afferents, and the excitability of intraspinal terminals of group II afferents, both of which are indices used to show presynaptic control. Conditioning stimulation of corticospinal pathways had no effects on the sizes of group II evoked FSPs in the midlumbar or sacral segments at either dorsal horn or intermediate zone locations. These stimuli also had no effect on the excitability of single group II afferent terminals in the dorsal horn of the midlumbar segments. As positive controls, we verified that the corticospinal conditioning stimuli used did effectively d
epress FSPs evoked from cutaneous afferents recorded at the same spinal locations as the group II field potentials in all experiments. Corticospinal tract conditioning stimuli did not consistently enhance or reduce the depression of group II FSPs that was evoked by stimulation of ipsilateral segmental group II or cutaneous afferents; in the large majority of cases there was no effect. The results reveal that the control of transmission of information from group II afferents in these regions of the spinal cord is independent of direct corticospinal control.},
web_url = {http://www.springerlink.com/content/95qj7938470405mh/fulltext.pdf},
state = {published},
DOI = {10.1007/s00221-008-1279-y},
author = {Aggelopoulos NC{aggelopoulos}{Department Physiology of Cognitive Processes}, Chakrabarty S and Edgley SA}
}

@Article{ 5176,
title = {The effect of a serotonin-induced dissociation between spiking and perisynaptic activity on BOLD functional MRI},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
year = {2008},
month = {5},
volume = {105},
number = {18},
pages = {6759-6764},
abstract = {The relationship of the blood oxygen-level-dependent (BOLD) signal to its underlying neuronal activity is still poorly understood. Combined physiology and functional MRI experiments suggested that local field potential (LFP) is a better predictor of the BOLD signal than multiunit activity (MUA). To further explore this relationship, we simultaneously recorded BOLD and electrophysiological activity while inducing a dissociation of MUA from LFP activity with injections of the neuromodulator BP554 into the primary visual cortex of anesthetized monkeys. BP554 is a 5-HT1A agonist acting primarily on the membrane of efferent neurons by potassium-induced hyperpolarization. Its infusion in visual cortex reliably reduced MUA without affecting either LFP or BOLD activity. This finding suggests that the efferents of a neuronal network pose relatively little metabolic burden compared with the overall presynaptic and postsynaptic processing of incoming afferents. We discuss implications of this finding for the interpretat
ion of BOLD activity.},
web_url = {http://www.pnas.org/cgi/reprint/105/18/6759},
state = {published},
DOI = {10.1073/pnas.0800312105},
author = {Rauch A{arauch}{Department Physiology of Cognitive Processes}, Rainer G{gregor} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5839,
title = {Facile Synthesis and Relaxation Properties of Novel Bispolyazamacrocyclic Gd3+ Complexes: An Attempt towards Calcium-Sensitive MRI Contrast Agents - Correction},
journal = {Inorganic Chemistry},
year = {2008},
month = {4},
volume = {47},
number = {8},
pages = {3460},
web_url = {http://pubs.acs.org/doi/pdfplus/10.1021/ic800450v},
state = {published},
DOI = {10.1021/ic800450v},
author = {Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Fouskov{\'a} P, Angelovski G{goran}{Department Physiology of Cognitive Processes}, Balogh E, Mishra AK{akmishra}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and T{\'o}th {\'E}}
}

@Article{ 5838,
title = {Interactions between the Superior Temporal Sulcus and Auditory Cortex Mediate Dynamic Face/Voice Integration in Rhesus Monkeys},
journal = {Journal of Neuroscience},
year = {2008},
month = {4},
volume = {28},
number = {17},
pages = {4457-4469},
web_url = {http://www.jneurosci.org/cgi/reprint/28/17/4457},
state = {published},
DOI = {10.1523/JNEUROSCI.0541-08.2008},
author = {Ghanzafar AA{asifg}{Department Physiology of Cognitive Processes}, Chandrasekaran C{chand} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 4894,
title = {Magnetic Resonance Imaging of Cortical Connectivity in vivo},
journal = {Neuroimage},
year = {2008},
month = {4},
volume = {40},
number = {2},
pages = {458-472},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WNP-4RC6R7X-4-S&_cdi=6968&_user=29041&_orig=search&_coverDate=04%2F01%2F2008&_sk=999599997&view=c&wchp=dGLbVtz-zSkzS&md5=dabfb44094d1137121dd895184e159cc&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.neuroimage.2007.12.007},
author = {Canals S{canals}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Keller AL{akeller}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 4951,
title = {Pharmacological MRI combined with electrophysiology in non-human primates: Effects of Lidocaine on primary visual cortex},
journal = {Neuroimage},
year = {2008},
month = {4},
volume = {40},
number = {2},
pages = {590-600},
abstract = {Pharmacological magnetic resonance imaging (phMRI) is a current direction in biomedical imaging, whose goal is the non-invasive monitoring of pharmacological manipulations on brain processes. We have developed techniques combining phMRI with simultaneous monitoring of electrophysiological activity during local injections of pharmacological agents into defined brain regions. We have studied effects of the local anesthetic Lidocaine on BOLD activity in primary visual cortex (V1) of non-human primates. Using independent component analysis (ICA), we describe and quantify the pharmacodynamics and spatial distribution of Lidocaine effects on visually evoked V1 BOLD signal in a dose-dependent manner. We relate these findings to effects of Lidocaine on neural activity as estimated by multi unit activity (MUA) and the local field potential (LFP). Our results open the way for specific fMRI-based investigations regarding the impact of pharmacological agents on the BOLD signal and its coupling to the underlying neuronal
activity.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WNP-4RC6R7X-6-S&_cdi=6968&_user=29041&_orig=search&_coverDate=04%2F01%2F2008&_sk=999599997&view=c&wchp=dGLbVtb-zSkWb&md5=adf47eeb2d65fc8d3b28e4cb66bfd411&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.neuroimage.2007.12.009},
author = {Rauch A{arauch}{Department Physiology of Cognitive Processes}, Rainer G{gregor}, Augath M{mark}{Department Physiology of Cognitive Processes}, Oeltermann A{axel} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5196,
title = {Sustained increase in hippocampal sharp-wave ripple activity during slow-wave sleep after learning},
journal = {Learning and Memory},
year = {2008},
month = {4},
volume = {15},
number = {4},
pages = {222-228},
abstract = {High-frequency oscillations, known as sharp-wave/ripple (SPW-R) complexes occurring in hippocampus during slow-wave sleep (SWS), have been proposed to promote synaptic plasticity necessary for memory consolidation. We recorded sleep for 3 h after rats were trained on an odor-reward association task. Learning resulted in an increased number SPW-Rs during the first hour of post-learning SWS. The magnitude of ripple events and their duration were also elevated for up to 2 h after the newly formed memory. Rats that did not learn the discrimination during the training session did not show any change in SPW-Rs. Successful retrieval from remote memory was likewise accompanied by an increase in SPW-R density and magnitude, relative to the previously recorded baseline, but the effects were much shorter lasting and did not include increases in ripple duration and amplitude. A short-lasting increase of ripple activity was also observed when rats were rewarded for performing a motor component of the task only. There were
no increases in ripple activity after habituation to the experimental environment. These experiments show that the characteristics of hippocampal high-frequency oscillations during SWS are affected by prior behavioral experience. Associative learning induces robust and sustained (up to 2 h) changes in several SPW-R characteristics, while after retrieval from remote memory or performance of a well-trained procedural aspect of the task, only transient changes in ripple density were induced.},
file_url = {/fileadmin/user_upload/files/publications/Learn%20&amp;amp;amp;%20Mem%202008_[0].pdf},
web_url = {http://learnmem.cshlp.org/cgi/reprint/15/4/222},
state = {published},
DOI = {10.1101/lm.726008},
author = {Eschenko O{oeschenko}{Department Physiology of Cognitive Processes}, Ramadan W, M\"olle M, Born J and Sara SJ}
}

@Article{ 4896,
title = {A voice region in the monkey brain},
journal = {Nature Neuroscience},
year = {2008},
month = {3},
volume = {11},
number = {3},
pages = {367-374},
abstract = {For vocal animals, recognizing species-specific vocalizations is important for survival and social interactions. In humans, a voice region has been identified that is sensitive to human voices and vocalizations. As this region also strongly responds to speech, it is unclear whether it is tightly associated with linguistic processing and is thus unique to humans. Using functional magnetic resonance imaging of macaque monkeys (Old World primates, Macaca mulatta) we discovered a high-level auditory region that prefers species-specific vocalizations over other vocalizations and sounds. This region not only showed sensitivity to the &amp;amp;lsquo;voice&amp;amp;lsquo; of the species, but also to the vocal identify of conspecific individuals. The monkey voice region is located on the superior-temporal plane and belongs to an anterior auditory what pathway. These results establish functional relationships with the human voice region and support the notion tha
t, for different primate species, the anterior temporal regions of the brain are adapted for recognizing communication signals from conspecifics.},
file_url = {/fileadmin/user_upload/files/publications/Petkov%20-%20Voice%20Area%20-%20NatureNeuro%20-%202008_4896[0].pdf},
web_url = {http://www.nature.com/neuro/journal/v11/n3/pdf/nn2043.pdf},
state = {published},
DOI = {10.1038/nn2043},
author = {Petkov CI{chrisp}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Steudel T{steudel}{Department Physiology of Cognitive Processes}, Whittingstall K{kevin}{Department Physiology of Cognitive Processes}, Augath M{mark}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5837,
title = {Category-specific responses to faces and objects in primate auditory cortex},
journal = {Frontiers in Systems Neuroscience},
year = {2008},
month = {3},
volume = {1},
number = {2},
pages = {1-8},
abstract = {Auditory and visual signals often occur together, and the two sensory channels are known to infl uence each other to facilitate perception. The neural basis of this integration is not well understood, although other forms of multisensory infl uences have been shown to occur at surprisingly early stages of processing in cortex. Primary visual cortex neurons can show frequency-tuning to auditory stimuli, and auditory cortex responds selectively to certain somatosensory stimuli, supporting the possibility that complex visual signals may modulate early stages of auditory processing. To elucidate which auditory regions, if any, are responsive to complex visual stimuli, we recorded from auditory cortex and the superior temporal sulcus while presenting visual stimuli consisting of various objects, neutral faces, and facial expressions generated during vocalization. Both objects and conspecifi c faces elicited robust fi eld potential responses in auditory cortex sites, but the responses varied by category: both neutral and vocalizing faces had a highly consistent negative component (N100) followed by a broader positive component (P180) whereas object responses were more variable in time and shape, but could be discriminated consistently from the responses to faces. The face response did not vary within the face category, i.e., for expressive vs. neutral face stimuli. The presence of responses for both objects and neutral faces suggests that auditory cortex receives highly informative visual input that is not restricted to those stimuli associated with auditory components. These results reveal selectivity for complex visual stimuli in a brain region conventionally described as non-visual “unisensory” cortex.},
web_url = {http://www.frontiersin.org/systemsneuroscience/paper/10.3389/neuro.06/002.2007/pdf/},
state = {published},
DOI = {10.3389/neuro.06.002.2007},
author = {Hoffman KL{kari}{Department Physiology of Cognitive Processes}, Ghanzafar AA{asifg}{Department Physiology of Cognitive Processes}, Gauthier I and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 4946,
title = {Inferring Spike Trains From Local Field Potentials},
journal = {Journal of Neurophysiology},
year = {2008},
month = {3},
volume = {99},
number = {3},
pages = {1461-1476},
abstract = {We investigated whether it is possible to
infer spike trains solely on the basis of the underlying local field
potentials (LFPs). Using support vector machines and linear regression
models, we found that in the primary visual cortex (V1) of
monkeys, spikes can indeed be inferred from LFPs, at least with
moderate success. Although there is a considerable degree of variation
across electrodes, the low-frequency structure in spike trains (in the
100-ms range) can be inferred with reasonable accuracy, whereas
exact spike positions are not reliably predicted. Two kinds of features
of the LFP are exploited for prediction: the frequency power of bands
in the high  gamma-range (40&amp;amp;amp;amp;amp;#8211;90 Hz) and information contained in lowfrequency
oscillations ( 10 Hz), where both phase and power modulations
are informative. Information analysis revealed that both
features code (mainly) independent aspects of the spike-to-LFP relationship,
with the low-frequency LFP phase coding for temporally
clustered spiking activity. Although both features and prediction
quality are similar during seminatural movie stimuli and spontaneous
activity, prediction performance during spontaneous activity degrades
much more slowly with increasing electrode distance. The general
trend of data obtained with anesthetized animals is qualitatively
mirrored in that of a more limited data set recorded in V1 of non-anesthetized
monkeys. In contrast to the cortical field potentials, thalamic LFPs
(e.g., LFPs derived from recordings in the dorsal lateral geniculate
nucleus) hold no useful information for predicting spiking activity.},
web_url = {http://jn.physiology.org/cgi/reprint/99/3/1461},
state = {published},
DOI = {doi:10.1152/jn.00919.2007},
author = {Rasch MJ{rasch}{Department Physiology of Cognitive Processes}, Gretton A{arthur}{Department Empirical Inference}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Maass W and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 4494,
title = {Natural vision reveals regional specialization to local motion and to contrast-invariant, global flow in the human brain.},
journal = {Cerebral Cortex},
year = {2008},
month = {3},
volume = {18},
number = {3},
pages = {705-717},
abstract = {Visual changes in feature movies, like in real-live, can be
partitioned into global flow due to self/camera motion, local/
differential flow due to object motion, and residuals, for example,
due to illumination changes. We correlated these measures with
brain responses of human volunteers viewing movies in an fMRI
scanner. Early visual areas responded only to residual changes,
thus lacking responses to equally large motion-induced changes,
consistent with predictive coding. Motion activated V51 (MT1),
V3A, medial posterior parietal cortex (mPPC) and, weakly, lateral
occipital cortex (LOC). V51 responded to local/differential motion
and depended on visual contrast, whereas mPPC responded to
global flow spanning the whole visual field and was contrast
independent. mPPC thus codes for flow compatible with unbiased
heading estimation in natural scenes and for the comparison of
visual flow with nonretinal, multimodal motion cues in it or
downstream. mPPC was functionally connected to anterior portions
of V51, whereas laterally neighboring putative homologue of
lateral intraparietal area (LIP) connected with frontal eye fields.
Our results demonstrate a progression of selectivity from local and
contrast-dependent motion processing in V51 toward global and
contrast-independent motion processing in mPPC. The function,
connectivity, and anatomical neighborhood of mPPC imply several
parallels to monkey ventral intraparietal area (VIP).},
web_url = {http://cercor.oxfordjournals.org/cgi/reprint/18/3/705},
state = {published},
DOI = {10.1093/cercor/bhm107},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}, Zeki S and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5115,
title = {Phase-of-Firing Coding of Natural Visual Stimuli in Primary Visual Cortex},
journal = {Current Biology},
year = {2008},
month = {3},
volume = {18},
number = {5},
pages = {375-380},
abstract = {We investigated the hypothesis that neurons encode rich naturalistic stimuli in terms of their spike times relative to the phase of ongoing network fluctuations rather than only in terms of their spike count. We recorded local field potentials (LFPs) and multiunit spikes from the primary visual cortex of anaesthetized macaques while binocularly presenting a color movie. We found that both the spike counts and the low-frequency LFP phase were reliably modulated by the movie and thus conveyed information about it. Moreover, movie periods eliciting higher firing rates also elicited a higher reliability of LFP phase across trials. To establish whether the LFP phase at which spikes were emitted conveyed visual information that could not be extracted by spike rates alone, we compared the Shannon information about the movie carried by spike counts to that carried by the phase of firing. We found that at low LFP frequencies, the phase of firing conveyed 54% additional information beyond that conveyed by spike counts.
The extra information available in the phase of firing was crucial for the disambiguation between stimuli eliciting high spike rates of similar magnitude. Thus, phase coding may allow primary cortical neurons to represent several effective stimuli in an easily decodable format.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6VRT-4S0GXTD-7-B&_cdi=6243&_user=29041&_orig=search&_coverDate=03%2F11%2F2008&_sk=999819994&view=c&wchp=dGLzVlz-zSkzk&md5=cb1a6bb2099bc83600ddc8cc9656be3b&ie=/sdarticle.pdf},
state = {published},
DOI = {http://dx.doi.org/10.1016/j.cub.2008.02.023},
author = {Montemurro MA, Rasch MJ{rasch}{Department Physiology of Cognitive Processes}, Murayama Y{yusuke}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Article{ 5834,
title = {Single-Trial Classification of Bistable Perception by Integrating Empirical Mode Decomposition, Clustering, and  Support Vector Machine},
journal = {EURASIP Journal on Advances in Signal Processing},
year = {2008},
month = {3},
volume = {2008},
number = {592742},
pages = {1-8},
abstract = {We propose an empirical mode decomposition (EMD-) based method to extract features from the multichannel recordings of local field potential (LFP), collected from the middle temporal (MT) visual cortex in a macaque monkey, for decoding its bistable structure-from-motion (SFM) perception. The feature extraction approach consists of three stages. First, we employ EMD to decompose nonstationary single-trial time series into narrowband components called intrinsic mode functions (IMFs) with time scales dependent on the data. Second, we adopt unsupervised K-means clustering to group the IMFs and residues into several clusters across all trials and channels. Third, we use the supervised common spatial patterns (CSP) approach to design spatial filters for the clustered spatiotemporal signals. We exploit the support vector machine (SVM) classifier on the extracted features to decode the reported perception on a single-trial basis. We demonstrate that the CSP feature of the cluster in the gamma frequency band outperforms the features in other frequency bands and leads to the best decoding performance. We also show that the EMD-based feature extraction can be useful for evoked potential estimation. Our proposed feature extraction approach may have potential for many applications involving nonstationary multivariable time series such as brain-computer interfaces (BCI).},
web_url = {http://www.hindawi.com/GetPDF.aspx?doi=10.1155/2008/592742},
state = {published},
DOI = {10.1155/2008/592742},
author = {Wang Z, Maier A{amaier}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Liang H}
}

@Article{ 5835,
title = {Single-Trial Decoding of Bistable Perception  Based on Sparse Nonnegative Tensor Decomposition},
journal = {Computational Intelligence and Neuroscience},
year = {2008},
month = {3},
volume = {2008},
number = {642387},
pages = {1-10},
abstract = {The study of the neuronal correlates of the spontaneous alternation in perception elicited by bistable visual stimuli is promising for understanding the mechanism of neural information processing and the neural basis of visual perception and perceptual decision-making. In this paper, we develop a sparse nonnegative tensor factorization-(NTF)-based method to extract features from the local field potential (LFP), collected from the middle temporal (MT) visual cortex in a macaque monkey, for decoding its bistable structure-from-motion (SFM) perception. We apply the feature extraction approach to the multichannel time-frequency representation of the intracortical LFP data. The advantages of the sparse NTF-based feature extraction approach lies in its capability to yield components common across the space, time, and frequency domains yet discriminative across different conditions without prior knowledge of the discriminating frequency bands and temporal windows for a specific subject. We employ the support vector machines (SVMs) classifier based on the features of the NTF components for single-trial decoding the reported perception. Our results suggest that although other bands also have certain discriminability, the gamma band feature carries the most discriminative information for bistable perception, and that imposing the sparseness constraints on the nonnegative tensor factorization improves extraction of this feature.},
web_url = {http://www.hindawi.com/GetPDF.aspx?doi=10.1155/2008/642387},
state = {published},
DOI = {10.1155/2008/642387},
author = {Wang Z, Maier A{amaier}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Liang H}
}

@Article{ 4808,
title = {The effect of labeling parameters on perfusion-based fMRI in nonhuman primates},
journal = {Journal of Cerebral Blood Flow and Metabolism},
year = {2008},
month = {3},
volume = {28},
number = {3},
pages = {640-652},
web_url = {http://www.nature.com/jcbfm/journal/v28/n3/pdf/9600564a.pdf},
state = {published},
DOI = {10.1038/sj.jcbfm.9600564},
author = {Zappe A-C{aczappe}{Department Physiology of Cognitive Processes}, Pfeuffer J{josef}{Department Physiology of Cognitive Processes}, Merkle H{hellmut}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Goense JBM{jozien}{Department Physiology of Cognitive Processes}}
}

@Article{ 4762,
title = {Facile Synthesis and Relaxation Properties of Novel Bis-polyazamacrocyclic Gd3+ Complexes: an Attempt towards Calcium Sensitive MRI Contrast Agents},
journal = {Inorganic Chemistry},
year = {2008},
month = {2},
volume = {47},
number = {4},
pages = {1370-1381},
abstract = {Three novel GdDO3A-type bismacrocyclic complexes, conjugated to Ca2+ chelating moieties like ethylenediaminetetraacetic acid and diethylenetriamine pentaacetic acid bisamides, were synthesized as potential “smart” magnetic resonance imaging contrast agents. Their sensitivity toward Ca2+ was studied by relaxometric titrations. A maximum relaxivity increase of 15, 6, and 32% was observed upon Ca2+ binding for Gd2L1, Gd2L2, and Gd2L3, respectively (L1 = N,N-bis{1-[{[({1-[1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane-10-yl]eth-
-yl}amino)carbonyl]methyl}-(carboxymethyl)amino]eth-2-yl}aminoacetic acid; L2 = N,N-bis[1-({[({α-[1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane-10-yl]-p-tolylamino}carbonyl)methyl]-(carboxymethyl)}amino)eth-2-yl]aminoacetic acid; L3 = 1,2-bis[{[({1-[1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane-10-yl]eth-2-yl}amino)carbonyl]methyl}(carboxymethyl)amino]ethane). The apparent association constants are log KA = 3.6 ± 0.1 for Gd2L1 and log KA = 3.4 ± 0.1 for Gd2L3. For the interaction between Mg2+ and Gd2L1, log KA = 2.7 ± 0.1 has been determined, while no relaxivity change was detected with Gd2L3. Luminescence lifetime measurements on the Eu3+ complexes in the absence of Ca2+ gave hydration numbers of q = 0.9 (Eu2L1), 0.7 (Eu2L2), and 1.3 (Eu2L3). The parameters influencing proton relaxivity of the Gd3+ complexes were assessed by a combined nuclear magnetic relaxation dispersion (NMRD) and 17O NMR study. Water exchange is relatively slow on Gd2L1 and Gd2L2 (kex298 = 0.5 and 0.8 × 106 s−1), while it is faster on Gd2L3 (kex298 = 80 × 106 s−1); in any case, it is not sensitive to the presence of Ca2+. The rotational correlation time, τR298, differs for the three complexes and reflects their rigidity. Due to the benzene linker, the Gd2L2 complex is remarkably rigid, with a correspondingly high relaxivity despite the low hydration number (r1 = 10.2 mM−1s−1 at 60 MHz, 298 K). On the basis of all available experimental data from luminescence, 17O NMR, and NMRD studies on the Eu3+ and Gd3+ complexes of L1 and L3 in the absence and in the presence of Ca2+, we conclude that the relaxivity increase observed upon Ca2+ addition can be mainly ascribed to the increase in the hydration number, and, to a smaller extent, to the Ca2+-induced rigidification of the complex.},
web_url = {http://pubs.acs.org/cgi-bin/article.cgi/inocaj/2008/47/i04/pdf/ic7017456.pdf},
state = {published},
DOI = {10.1021/ic7017456},
author = {Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Fouskov{\'a} P, Angelovski G{goran}{Department Physiology of Cognitive Processes}, Balogh E, Mishra AK{akmishra}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and T{\'o}th {\'E}}
}

@Article{ 4824,
title = {fMRI of the temporal lobe of the awake monkey at 7 T},
journal = {NeuroImage},
year = {2008},
month = {2},
volume = {39},
number = {3},
pages = {1081-1093},
abstract = {Increasingly 7 T scanners are used for fMRI of humans and non-human primates, promising improvements in signal-to-noise, spatial resolution and specificity. A disadvantage of fMRI at 7 T, but already at 3 T, is that susceptibility artifacts from air-filled cavities like the ear canal and nasal cavity cause signal loss and distortion. This limits the applicability of fMRI in these areas, thereby limiting study of these areas, but it also limits study of processes that span large-scale cortical networks or the entire brain. Our goal is to study the inferior temporal (IT) lobe in awake monkeys because of its importance in object perception and recognition, but the functional signal is degraded by strong susceptibility gradients. To allow fMRI of this region, we used an optimized SE-EPI, which recovers signal lost with GE-EPI and we corrected for susceptibility-induced image distortion. SE-EPI has the added advantage that, in contrast to GE-EPI, where the functional signal derives to a large extent from veins, th
e SE-EPI signal arises from the microvasculature, and hence it better represents the neural activation. We show fMRI at 7 T of the entire visual pathway in the awake primate with robust and widespread activation in all ventral areas of the brain, including areas adjacent to the ear canal. This allows fMRI of areas that normally suffer from artifact and thus more reliable whole-brain studies.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WNP-4PT2960-1-S&_cdi=6968&_user=29041&_orig=search&_coverDate=10%2F01%2F2007&_sk=999999999&view=c&wchp=dGLbVzb-zSkWA&md5=f951a759c6655f02492ab5f09f1a9e42&ie=},
state = {published},
DOI = {10.1016/j.neuroimage.2007.09.038},
author = {Goense JBM{jozien}{Department Physiology of Cognitive Processes}, Ku S-P{shihpi}{Department Physiology of Cognitive Processes}, Merkle H{hellmut}, Tolias AS{atolias}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Article{ 5067,
title = {Localizing cortical computations during visual selection},
journal = {Neuron},
year = {2008},
month = {2},
volume = {57},
number = {4},
pages = {480-481},
abstract = {Local field potentials (LFPs) and spikes are two signals that can be recorded from the brain using extracellular microelectrodes. A study by Monosov et al. in this issue of Neuron using timing relations between these signals suggests that selection of a target from an array of distractors is a computational operation performed specifically and locally in the frontal eye field (FEF).},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WSS-4RXTNW3-3-1&_cdi=7054&_user=29041&_orig=search&_coverDate=02%2F28%2F2008&_sk=999429995&view=c&wchp=dGLbVzz-zSkzS&md5=aa4468ee7b1103cd8f34cdaffd30ee89&ie=},
state = {published},
DOI = {10.1016/j.neuron.2008.02.002},
author = {Rainer G{gregor}}
}

@Article{ 5008,
title = {Neuroanatomy},
journal = {Scholarpedia},
year = {2008},
month = {2},
volume = {3},
number = {3},
pages = {3158},
abstract = {All nervous systems consist of astonishingly similar elements, the nerve cells or neurons. Despite this fact, nervous systems of different animal classes can be organized in strikingly different ways, and in individual brains different anatomical structures can be made out that are obviously related to different functions. In some of these brain parts, one can easily draw conclusions from their particular structure onto the particular kind of information processing in them.},
web_url = {http://www.scholarpedia.org/article/Neuroanatomy},
booktitle = {Scholarpedia},
state = {published},
DOI = {10.4249/scholarpedia.3158},
author = {Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}}
}

@Article{ 4796,
title = {Object features used by humans and monkeys to identify rotated shapes},
journal = {Journal of Vision},
year = {2008},
month = {2},
volume = {8},
number = {2:9},
pages = {1-15},
abstract = {Humans and rhesus monkeys can identify shapes that have been rotated in the picture plane. Recognition of rotated shapes can be as efficient as recognition of upright shapes. Here we investigate whether subjects showing view-invariant performance use the same object features to identify upright and rotated versions of a shape. We find marked differences between humans and monkeys. While humans tend to use the same features independent of shape orientation, monkeys use unique features for each orientation. Humans are able to generalize to a greater degree across orientation changes than rhesus monkey observers, who tend to relearn separate problems at each orientation rather than flexibly apply previously learned knowledge to novel problems.},
web_url = {http://journalofvision.org/8/2/9/Nielsen-2008-jov-8-2-9.pdf},
state = {published},
DOI = {10.1167/8.2.9},
author = {Nielsen KJ{kristina}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Article{ 4695,
title = {Towards extracellular Ca2+ sensing by MRI: synthesis and calcium-dependent 1H and 17O relaxation studies of two novel bismacrocyclic Gd3+ complexes.},
journal = {Journal of Biological Inorganic Chemistry},
year = {2008},
month = {1},
volume = {13},
number = {1},
pages = {35-46},
abstract = {Two new bismacrocyclic Gd3+ chelates containing a specific Ca2+ binding site were synthesized as potential MRI contrast agents for the detection of Ca2+ concentration changes at the millimolar level in the extracellular space. In the ligands, the Ca2+-sensitive BAPTA-bisamide central part is separated from the DO3A macrocycles either by an ethylene (L1) or by a propylene (L2) unit [H4BAPTA is 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid; H3DO3A is 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid]. The sensitivity of the Gd3+ complexes towards Ca2+ and Mg2+ was studied by 1H relaxometric titrations. A maximum relaxivity increase of 15 and 10% was observed upon Ca2+ binding to Gd2L1 and Gd2L2, respectively, with a distinct selectivity of Gd2L1 towards Ca2+ compared with Mg2+. For Ca2+ binding, association constants of log K = 1.9 (Gd2L1) and log K = 2.7 (Gd2L2) were determined by relaxometry. Luminescence lifetime measurements and UV–vis spectrophotometry on the corresponding Eu3+ analogues proved that the complexes exist in the form of monohydrated and nonhydrated species; Ca2+ binding in the central part of the ligand induces the formation of the monohydrated state. The increasing hydration number accounts for the relaxivity increase observed on Ca2+ addition. A 1H nuclear magnetic relaxation dispersion and 17O NMR study on Gd2L1 in the absence and in the presence of Ca2+ was performed to assess the microscopic parameters influencing relaxivity. On Ca2+ binding, the water exchange is slightly accelerated, which is likely related to the increased steric demand of the central part leading to a destabilization of the Ln–water binding interaction.},
web_url = {http://www.springerlink.com/content/x6710238n520p152/fulltext.pdf},
state = {published},
DOI = {10.1007/s00775-007-0296-9},
author = {Dhingra K{kirti}{Department Physiology of Cognitive Processes}, Fouskov{\'a} P, Angelovski G{goran}{Department Physiology of Cognitive Processes}, Maier ME, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and T{\'o}th {\'E}}
}

@Inproceedings{ 5040,
title = {Gesichtswahrnehmung: interdisziplinäre Einsichten},
year = {2008},
month = {3},
pages = {63-66},
web_url = {http://www.teap.de/index.php/teap/marburg2008},
editor = {Khader, P. , K. Jost, H. Lachnit, F. Röster},
publisher = {Pabst Science Publ.},
address = {Lengerich, Germany},
event_name = {50. Tagung Experimentell Arbeitender Psychologen (TeaP 2008)},
event_place = {Marburg, Germany},
state = {published},
ISBN = {978-3-89967-457-6},
author = {Dahl CD{dahl}{Department Physiology of Cognitive Processes}, M\"oller S, Veres-Injac B and Wallraven C{walli}}
}

@Inbook{ 4317,
title = {Using spikes and local field potentials to reveal computational networks in monkey cortex},
year = {2008},
month = {11},
pages = {350-362},
abstract = {Traditionally, neurophysiological investigations in awake non-human primates have largely focused on the study of single-unit activity (SUA), recorded extracellularly in behaving animals using microelectrodes. The general aim of these studies has been to uncover the neural basis of cognition and action by elucidating the relation between brain activity and behavior. This is true for studies in sensory systems such as the visual system, where investigators are interested in how SUA covaries with aspects of visually presented stimuli, as well as for studies in the motor system where SUA covariation with movement targets and dynamics are investigated. In addition to these SUA studies, there has been increasing interest in the local field potential (LFP), a signal that reflects aggregate activity across populations of neurons near the tip of the microelectrode. In this chapter, we will describe recent progress in our understanding of brain function in awake behaving monkeys using LFP recordings. We will show that the combination of recording the activity of single neurons and local populations simultaneously offers a particularly promising way to gain insight into cortical brain mechanisms underlying cognition and memory.},
web_url = {http://ebooks.cambridge.org/chapter.jsf?bid=CBO9780511541650&cid=CBO9780511541650A024},
editor = {Hölscher, C. , M. Munk},
publisher = {Oxford University Press},
address = {Oxford, England},
booktitle = {Information processing by neuronal populations},
state = {published},
ISBN = {978-0-521-87303-1},
DOI = {10.1017/CBO9780511541650.014},
author = {Nielsen KJ{kristina}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Inbook{ 4646,
title = {Lost without a map: Pursuing primate homologies with functional imaging},
year = {2008},
pages = {175-194},
web_url = {https://www.novapublishers.com/catalog/product_info.php?cPath=23_131_104&products_id=6193&osCsid=2fd62a5ac914cbc0483f60dc36c7e958},
editor = {Liang, Y.},
publisher = {Nova Science Publ.},
address = {New York, NY, USA},
series = {Nova Biomedical},
booktitle = {Research topics on brain mapping},
state = {published},
ISBN = {978-1-60456-001-5},
author = {Petkov CI{chrisp}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5695,
title = {A comparison of the information about rich naturalistic stimuli carried by phase and power of LFP recordings},
year = {2008},
month = {11},
volume = {38},
number = {397.7},
abstract = {Local field potentials (LFPs) reflect sub-threshold integrative processes that complement spike train measures. Here we investigate how LFPs encode rich naturalistic sensory stimuli. We addressed this question by recording LFPs from the primary visual cortex of anesthetized macaques with an array of electrodes while presenting binocularly a color movie. The electrodes were arranged in a 4 by 4 matrix and interelectrode spacing varied from 1 to 2.5 mm. We decomposed the LFP into narrow frequency bands (1-4Hz, 4-8Hz, 8-12Hz and up to 100Hz in 4-Hz wide non-overlapping frequency intervals by using standard bandpassing techniques. We then computed the amount of information about the movie that is carried by the phase or by the instantaneous power of the bandpassed LFP obtained from each individual electrode. When considering the information in LFP power, we found that the instantaneous power was most informative in the low frequency range (< 8 Hz) and in the high gamma frequency range (60-100 Hz). When considering the LFP phase, we found that only the phase of low frequency LFPs (< 12 Hz) was informative about the movie. We found that phase was more informative about the movie than power was. On average across all recording sites and experimental animals, the maximum across LFP frequencies of information about the movie that could be extracted from LFP phase was approximately 0.4 bits, whereas the maximum across LFP frequencies of information about the movie that could be extracted from LFP power was approximately 0.2 bits. We finally investigated whether the phase or power or LFPs recorded from different electrodes convey similar or different information about the movie. Our preliminary results suggest that the informative parts of the LFP signal, i.e. low frequency phases, low frequency power and high gamma power have stimulus selectivity that remains largely similar (though not identical) across the range of distances covered by the electrode grid. Currently we are investigating how phase and power of LFPs encodes stimuli in auditory cortex.},
web_url = {http://www.sfn.org/am2008/},
event_name = {38th Annual Meeting of the Society for Neuroscience (Neuroscience 2008)},
event_place = {Washington, DC, USA},
state = {published},
author = {Belitski A{belitski}{Department Physiology of Cognitive Processes}, Montemurro M, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Panzeri S{stefano}}
}

@Poster{ WehrhahnD2008,
title = {Color AND motion are what the eye sees best},
year = {2008},
month = {11},
volume = {38},
number = {459.14},
abstract = {Watson, Barlow and Robson (1983) argued that the visual stimulus which humans detect best specifies the spatio-temporal structure of the receptive field of the most sensitive visual neurons in the human brain. To investigate 'what the eye sees best' they used various achromatic stimuli (squares, spots and gratings) and found that drifting grating patches were seen best by their observers.
A decade later Chaparro, Stromeyer, Huang, Kronauer and Eskew (1993) reexamined this idea using flashed circular spots whose spectral content could be changed. Their best chromatic stimulus was seen 5 - 9 fold better than their best luminance spot and 3-8-fold better than Watson's best stimulus.
Here we report experiments with a rectangular stimulus containing two vertically oriented edges of 20 min of arc height. Chromaticity of the edges was chosen from a set of 16 equally detectable colors which covered the whole gamut of color available on a video monitor. For each observer, these colors were adjusted to be equiluminant with respect to the grey background using flicker fusion photometry. Observers fixated a spot in the center of the stimulus such that the two vertical edges were seen at about 1 deg. eccentricity to the left and to the right. After initial fixation of 0.5 sec, the stimulus was presented in one of the 16 colors. After .5 s., at random, one of the vertical edges (left or right) jumped to the left or right and stayed there for another .5 s. Subjects were instructed to report (1) on which side relative to the fixation spot the edge had moved, irrespective of its direction and (2) its direction of motion.
For all observers 16 colors were found, for which they correctly reported the direction of motion of the edge, while failing to reliably detect the location of motion irrespective of its direction. Quantitatively, we found that contrast thresholds for identification of the direction of motion were about half of those for detecting the side at which motion was presented or for flashed stimuli of the same chromatic content.
As a control we also ran experiments where achromatic edges of various contrasts were presented on the same grey background to the same observers. Now all subjects performed equally well in both tasks.
Thus, the high sensitivity for the direction of motion of an edge found in our experiments is due to both the chromatic contents of the stimuli, as well as the spatio-temporal interactions extracting the direction of motion. Comparable results of experiments where the moving edge was presented to the central fovea were described by Kremers, Wachtler, Wehrhahn, Lee & Zrenner (1993). We conclude that the stimulus that the eye sees (so far) best, is the direction of a chromatic moving edge.},
web_url = {http://www.sfn.org/am2008/},
event_name = {38th Annual Meeting of the Society for Neuroscience (Neuroscience 2008)},
event_place = {Washington, DC, USA},
state = {published},
author = {Wehrhahn CF{wehrhahn}{Department Physiology of Cognitive Processes} and Dillenburger B{babs}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5293,
title = {Neural correlates of visual self-motion cues and visual pursuit investigated using fMRI},
year = {2008},
month = {11},
volume = {38},
number = {461.19},
abstract = {For the successful estimation of self-motion based on visual cues it is necessary to take self-induced motion signals into account, such as those induced by eye-movements. In this fMRI study we used stimulus conditions that allowed us to differentiate neural responses to (a) retinal motion, (b) eye-movements (visual pursuit) and (c) objective motion. Responses to these three motion cues were measured in context of two types of visual stimuli, namely moving 2D dot-sheets and 3D-expanding flow fields. An additional localizer experiment segregated responses to contra- and ipsi-lateral stimulation as well as to full field coherent expansion as opposed to trajectory matched scrambled random motion. We found that MT/V5 and MST responded primarily to retinal motion and to eye-movements. More parietal regions such as V7 and IPS (intra-parietal sulcus) and a region recently implicated in self-motion processing, the cingulate sulcus visual area (CSv), seem to be driven by all three motion cues. The localizer experiment revealed that all of these regions responded almost exclusively to coherent motion types, while MT+/V5+ also responded, but less strongly, to the matched random motion display. CSv differed from all other regions in that it favored 2D translational coherent motion over 3D expanding flow fields, and in that its responses to ipsi- and contralateral flow were indistinguishable. It thus appears to be a strong candidate for integrating translational motion signals of retinal and non-retinal origin. Area V3A/B differed from most other motion processing regions in that it was primarily affected by objective motion, and also, but less, by visual pursuit. Furthermore, in the localizer it responded equally to coherent 3D flow and to the random motion stimulus. This suggests that V3A/B processes differential rather than coherent or self-induced motion. Our results lead us to suggest that there is a clear functional segregation among higher level motion processing regions in context of self-motion processing cues. It remains to be resolved to which extent the distinct regions inter-operate in a hierarchical or rather in a parallel fashion.},
web_url = {http://www.sfn.org/am2008/},
event_name = {38th Annual Meeting of the Society for Neuroscience (Neuroscience 2008)},
event_place = {Washington, DC, USA},
state = {published},
author = {Fischer E{efischer}{Department Physiology of Cognitive Processes}, B\"ulthoff HH{hhb}{Department Human Perception, Cognition and Action}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5602,
title = {Tetrode recording of local neuronal ensembles provides insight into coding mechanisms of short-term memory in macaque prefrontal cortex},
year = {2008},
month = {11},
volume = {38},
number = {296.5},
abstract = {As most cortical neurons are broadly tuned to various stimulus parameters, it is inevitable that individual neurons participate in the representation of more than one visual object. Vice versa, accurate representations of individual objects for example in short-term memory that can support reliable decisions require the participation of large neuronal populations. To provide evidence in favor of population codes, we have recently analyzed simultaneously recorded multi- and single-unit signals derived from arrays of single-ended microelectrodes (Waizel et al., SfN 2007). Multi-contact electrodes like tetrodes (tts) which have a real 3D-structure provide signals that allow for estimating the position of the recorded neurons by triangulation. Here we set out to study whether recording from 3D-tts would improve the quality of sorting and hence allow for the extraction of more information about the stimulus. Based on single trial firing rate values, we calculated one-way ANOVAs at 1% significance thresholds and performed subsequent posthoc comparison (Scheffé) in order to detect stimulus selectivity and determine stimulus specificity for the activity at each single site, respectively. In order to investigate the coding of distributed neuronal ensembles, we computed binary activity patterns for all active electrodes in the array and determined their stimulus selectivity and specificity. Compared to what we found previously in single microelectrode recordings, the number of object selective or even specific recording sites increased up to 3 times which provides highly specific sites in 3 out of 4 sessions (3000 trials, 13.5 million spikes). Given that our monkeys always performed the memory task with a set of twenty visual stimuli, we found highly specific sites coding for only one object which revealed up to 18 of 19 possible pairwise comparisons. According to the proposal that single neurons participate in more than one specific object representation we also found bi- or even tri-object-dependant sites (average 27 significant pairwise comparisons per session) and never non-systematic object specificity. As clusters of triangulation-reconstructed spikes tend to have inter-cluster regions with smooth transitions which could potentially reflect synchronous spikes, we wanted to know how much information could be carried by these signals. After removing spikes between clusters, we found object specificity highly decreased (in one session only 6 out of previous 38 significant pairwise comparisons remained). These results suggest that the use of tetrodes with a real 3D-structure provides more information about neuronal object representations.},
web_url = {http://www.sfn.org/am2008/},
event_name = {38th Annual Meeting of the Society for Neuroscience (Neuroscience 2008)},
event_place = {Washington, DC, USA},
state = {published},
author = {Waizel M{waizel}{Department Physiology of Cognitive Processes}, Staedtler E, Pipa G, Chen N-H and Munk MJH{munk}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6098,
title = {Timing of local field potential (LFP) responses in primate inferior temporal (IT) cortex distinguishes between monkey faces, human faces and objects},
year = {2008},
month = {11},
volume = {38},
number = {261.14},
abstract = {It is well established that the inferior temporal (IT) cortex of the macaque monkey contains cells that respond selectively to faces. How information about faces is represented and organized at the network level remains largely unknown. Here we simultaneously recorded local field potentials (LFPs) and spiking activity in the IT cortex of two monkeys fixating at realistic human, monkey faces and objects, to investigate the neural representation of these stimulus classes. Our previous results indicate that spike information recorded from single neurons clearly differentiates between these three classes of stimuli. Here we investigate whether LFPs also contain information about these three types of stimuli. From the visual evoked potentials (VEP), we reliably and automatically extracted (in 44/65 sites in monkey M1 and in 20/68 sites in monkey 20) different features that convey time or amplitude information about stimulus class. Specifically, we focused on the timing and amplitude of the so called “N70” (negative deflection after about 70 ms of stimulus presentation), “P100” (positive deflection at about 100 ms) and “N170” (positive deflection at about 170 ms) components of the VEP. We grouped the VEPs into three classes according to the stimulus: humans, monkeys and objects VEPs. We found in both monkeys that the onset time of the face VEPs was significantly faster compared to the object VEPs (ttests, P<0.01) for all three deflections. Moreover, the onset of these deflections was faster for the monkey face VEPs compared to the human face VEPs (ttests, P<0.05). By contrast, the amplitude of these deflections did not systematically vary between stimulus classes. These results suggest that timing information in the LFPs can be used to reliably discriminate between human and monkey face stimuli. Furthermore, activation evoked by monkey faces reaches IT cortex earlier than the one evoked by human faces. These findings suggest a privileged role for processing of own species faces in the macaque brain.},
web_url = {http://www.sfn.org/am2008/},
event_name = {38th Annual Meeting of the Society for Neuroscience (Neuroscience 2008)},
event_place = {Washington, DC, USA},
state = {published},
author = {Sigala Alanis GR{sigala}{Department Physiology of Cognitive Processes}, Veit J{jveit}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ 6109,
title = {Voice Region Connectivity in the Monkey Assessed with Microstimulation and Functional Imaging},
year = {2008},
month = {11},
volume = {38},
number = {850.2},
abstract = {A “voice” region has recently been identified in the monkey auditory cortex with functional magnetic resonance imaging (fMRI) and electrophysiology, which shows a close functional correspondence to the known human-voice region. Both human and monkey voice regions lie anterior and superior on the temporal lobe and strongly prefer species-specific vocalizations over other categories of sounds and acoustical controls. The human and monkey voice regions are also sensitive to vocal differences among individuals and appear to be important centers for vocal sound processing within a network that is poorly understood. To clarify the in-vivo functional connectivity of the voice region in the rhesus monkey we used microstimulation in combination with high-resolution fMRI. First we functionally localized the voice region with blood-oxygen-level-dependent (BOLD) fMRI, as previously described. Then we microstimulated the voice region with glass-coated iridium microelectrodes, using biphasic, cathode leading, 250 to 500 μA pulses of 200 μs duration. We used the BOLD response to evaluate the anterograde targets of the microstimulation site. Microstimulation of the monkey voice region, which lies on the rostral superior-temporal plane (rSTP), elicited a BOLD response from hierarchically earlier auditory areas (feed-back), and the surrounding superior-temporal-plane (STP), -gyrus (STG) and -sulcus (STS) of the ipsilateral hemisphere. We observed no direct targets in the prefrontal cortex from voice region microstimulation, so we hypothesized that voice information might reach the frontal cortex indirectly. To test this idea we microstimulated a region in the upper bank of the STS that was one of the direct targets of the voice region, which resulted in medial and orbital prefrontal cortex activity, and neighboring regions on the STP, STG, STS and temporal pole. Our initial observations suggest that acoustical information from the voice region reaches the frontal cortex indirectly via other rostro-temporal regions such as the STS. Since the primate STS receives multisensory input and is known to contain face-recognition regions, we propose that voice information is paired with face information in the anterior temporal lobe before being transmitted to the prefrontal cortex.},
web_url = {http://www.sfn.org/am2008/},
event_name = {38th Annual Meeting of the Society for Neuroscience (Neuroscience 2008)},
event_place = {Washington, DC, USA},
state = {published},
author = {Kikuchi Y, Rauschecker JP, Mishkin M, Augath M{mark}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Petkov CI{chrisp}}
}

@Poster{ 5484,
title = {A 200 MHz flexible receive phased array for (f)MRI of macaques in a vertical scanner},
journal = {Magnetic Resonance Materials in Physics, Biology and Medicine},
year = {2008},
month = {10},
volume = {21},
number = {Supplement 1},
pages = {654-655},
abstract = {Introduction: Since high SNR is necessary for high-resolution FMRI it is
advantageous to place the coils close against the monkey’s head whenever
possible. To this end, we designed a flexible 4-channel receive-only phased
array that can be used on monkeys of different sizes as well as for different
cortical areas. In addition, the preamplifiers including control electronics are detachable and can serve a variety of prefabricated and phase-matched fourelement
arrays of different configurations.
Methods: A linear array of 4 circular coils of ~23 mm diameter with gaps of
~11 mm was sutured onto a soft plastic strip (Figure 1). The assembly having
in-line connectors was attached to phase-matched coaxial cables to modified
commercial high reflection coefficient preamplifiers (Stark Contrast
Inc., Erlangen, Germany) via cable traps. Detuning of the individual coils
during RF transmission was achieved using DC currents within the coaxial
cables and pin diode controlled notch filters within the array elements.
Experiments were done on anesthetized monkeys on a vertical 4.7T Bruker
Biospec running ParaVision 5. The array was positioned over the occipital
pole. RF transmission was done with a de-tunable ‘type D’ partial volume
coil. We obtained high-resolution FLASH (Figure 2) and FMRI data using
EPI with and without acceleration (GRAPPA). The stimulus was a full-field
rotating checkerboard. FLASH: resolution 100x100x1000 μm, TE 23 ms, TR
2000 ms, 1 average; FMRI: GE-EPI, resolution 500x500x2000 μm, TE 21 ms,
TR 750 ms, 8 segments with R = 1, or 4 segments with R = 2.
Results: The high-resolution FLASH anatomical images show intracortical
veins and the Gennari line in entire V1, including peripheral V1, which is located
deep in the brain. Using a dual-coil setup, it is only possible to observe
these features in parts of V1 that are close to the surface. The functional map
proofs that the increased coverage allows us to obtain activation in V1-V5 in
both hemispheres at high resolution (Figure 3). SNR was sufficient to also
allow accelerated FMRI at the same resolution.
Discussion: Compared to a dual-coil setup the phased array provides improved
SNR and coverage, which allows for high resolution anatomical imaging
and FMRI of the entire early visual cortex, including better performance
in deep brain areas.},
web_url = {http://www.esmrmb.org/index.php?id=/en/esmrmb_congress_2008.htm},
event_name = {ESMRMB 2008 Congress: 25th Annual Meeting},
event_place = {Valencia, Spain},
state = {published},
DOI = {10.1007/s10334-008-0126-2},
author = {Merkle H{hellmut}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Goense JBM{jozien}{Department Physiology of Cognitive Processes}}
}

@Poster{ KostenGBK2008,
title = {Going to temporal superresolution for AP detection in two{photon calcium imaging in vivo by using an explicit datamodel},
year = {2008},
month = {10},
volume = {9},
number = {12},
abstract = {Two{photon calcium imaging in vivo allows for the simultaneous imaging of activity in
populations of cortical neurons. This approach has been shown to achieve both single
action{potential (AP) and single{cell resolution, an important requirement when measuring
neural activity. However, there still remains room for improvement in both data
acquisition and data analysis. Imaging calcium transients across time allows the inference
of electrical spiking activity, but since the calcium signals are an order of magnitude slower
than the spiking activity which produces them, temporal accuracy can be lost. Here we
describe a possible approach to increase the temporal resolution of such data. We present
an approach that explicitly models signal and noise in the data, and complements the
output of a previous spike detection algorithm. Instead of averaging the signal over 96 ms
(a full frame), we employ higher resolution that averages over 1.5 ms periods, corresponding
to the individual laser scan lines that compose a single image frame. The dierence
between theoretical and observed 
uorescence measurements is modeled as a multivariate
Gaussian distribution with zero mean, yielding a likelihood value for each possible spike
time over a two frame window. Taking into account the prior distribution of timing errors
in the output of our AP detection algorithm, we estimate the detected spike's most likely
position. This approach improves temporal resolution signicantly compared to previous
methods. We discuss the future development of this approach, its limitations, and the
crucial role of an accurate estimation of baseline 
uorescence.},
web_url = {http://www.neuroschool-tuebingen-nena.de/index.php?id=284},
event_name = {9th Conference of the Junior Neuroscientists of Tübingen (NeNa 2008)},
event_place = {Ellwangen, Germany},
state = {published},
author = {Kosten J{jkosten}{Department High-Field Magnetic Resonance}, Greenberg D{david}{Research Group Neural Population Imaging}, Bethge M{mbethge}{Research Group Computational Vision and Neuroscience} and Kerr J{jkerr}{Research Group Neural Population Imaging}}
}

@Poster{ PerrodinKLP2008,
title = {Multisensory integration of dynamic voices and faces in the monkey brain},
year = {2008},
month = {10},
volume = {9},
number = {8},
abstract = {Primates are social animals whose communication is based on their conspecics' vocalizations
and facial expressions. Although a lot of work to date has studied the unimodal
representation of vocal or facial information, little is known about the way the nervous
system supports the processing of communication signals from dierent sensory modalities
to combine them into a coherent audiovisual percept. It is thought that the brains
of human and nonhuman primates evaluate vocal expressions and facial information separately
in specialized 'voice' and 'face' brain regions but we wondered if cross{sensory
interactions were already evident at the neuronal level in these typically unimodal brain
regions.
Using movies of vocalizing humans and monkeys as stimuli, we recorded extracellularly
from the auditory cortex of a macaque monkey, targeting his 'voice' region in the right
hemisphere. Within a multi{factorial design we evaluated how these auditory neurons responded
to dierent sensory modalities (auditory or visual) or combinations of modalities
(audiovisual). We also analyzed the responses for species{specic eects (human/ monkey
speaker), call type specicity (coo/ grunt), as well as speaker familiarity, size and identity.
Following the approach in the original fMRI study localizing the monkey voice region,
our recordings identied a voice area 'cluster' in this animal. Within this auditory cluster
of sites, we observed a signicant visual in
uence on both the local{eld potential (LFP)
and the spiking activity (AMUA), and found that 30% of the sites showed audiovisual
interactions in the LFP signals, and 38% in the AMUA. Grunts were especially eective
stimuli for this region and rather than a specialization for monkey vocalizations, human
vocalizations also elicited strong responses.
Our results provide evidence for visual in
uences in what has been characterized as an
auditory 'voice' area suggesting that at least the 'voice' regions are in
uenced by the
visual modality. Voices and faces seem to already interact at traditionally unisensory
brain areas, rather than cross{sensory information being combined only in higher-level,
associative or multisensory regions of the brain.},
web_url = {http://www.neuroschool-tuebingen-nena.de/index.php?id=284},
event_name = {9th Conference of the Junior Neuroscientists of Tübingen (NeNa 2008)},
event_place = {Ellwangen, Germany},
state = {published},
author = {Perrodin C{cperrodin}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Petkov CI{chrisp}}
}

@Poster{ FischerBLB2008,
title = {Neural correlates of visual self-motion cues and visual pursuit investigated using fMRI},
year = {2008},
month = {10},
volume = {9},
number = {5},
abstract = {For the successful estimation of self-motion based on visual cues it is necessary to take self-induced motion signals into account, such as those induced by eye-movements. In this fMRI study we used stimulus conditions that allowed us to differentiate neural responses to (a) retinal motion, (b) eye-movements (visual pursuit) and (c) objective motion. Responses to these three motion cues were measured in context of two types of visual stimuli, namely moving 2D dot-sheets and 3D-expanding ow fields. An additional localizer experiment segregated responses to contra- and ipsi-lateral stimulation as well as to full field coherent expansion as opposed to trajectory matched scrambled random motion. We found that MT/V5 and MST responded primarily to retinal motion and to eye-movements. More parietal regions such as V7 and IPS 
(intra-parietal sulcus) and a region recently implicated in self-motion processing, the cingulate sulcus visual area (CSv), seem to be driven by all three motion cues. The 
localizer experiment revealed that all of these regions responded almost exclusively to coherent motion types, while MT+/V5+ also responded, but less strongly, to the 
matched random motion display. CSv differed from all other regions in that it favored 2D translational coherent motion over 3D expanding  ow fields. Also, its responses to 
ipsi and contralateral ow were indistinguishable. It thus appears to be a strong candidate for integrating translational motion signals of retinal and non-retinal origin. Area V3A/B differed from most other motion processing regions in that it was primarily affected by objective motion, and also, but less, by visual pursuit. Furthermore, in the localizer it responded equally to coherent 3D now and to the random motion stimulus. This suggests that V3A/B processes differential rather than coherent or self-induced motion. Our results lead us to suggest that there is a clear functional segregation among higher level motion processing regions in context of self-motion processing cues. It remains to be resolved to which extent the distinct regions inter-operate in a hierarchical or rather in a parallel fashion.},
web_url = {http://www.neuroschool-tuebingen-nena.de/index.php?id=284},
event_name = {9th Conference of the Junior Neuroscientists of Tübingen (NeNa 2008)},
event_place = {Ellwangen, Germany},
state = {published},
author = {Fischer E{efischer}{Department Physiology of Cognitive Processes}, B\"ulthoff HH{hhb}{Department Human Perception, Cognition and Action}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5544,
title = {Decoding the perceptual boundary of human/monkey face categories from a population of neurons in the Inferior-Temporal (IT) cortex of the macaque monkey brain},
journal = {Frontiers in Neuroinformatics},
year = {2008},
month = {9},
number = {Conference Abstract: Neuroinformatics 2008},
abstract = {Faces have been intensively used in human and monkey subjects to study visual perception. However, due to the different approaches scientists have had to follow given the implicit differences in these two types of observers, there are few studies comparing face perception in both species, especially perceptual effects in humans and single cell recordings in behaving monkeys. Using a new computer vision algorithm based on Support Vector Machines (SVMs) we created realistic morphs by linearly interpolating three-dimensional information of human and monkey faces. We asked human observers to categorize these morphs as humans or monkeys and we found that they draw the category boundary closer to their own species (at approximately 60%human/40%monkey). We looked for the neural correlates of this effect recording the single-unit-activity (SUA) of neurons (194 in monkey M1 and 220 in monkey M2) in the IT cortex of two macaque monkeys while they fixate at those faces. Considering all recorded neurons, 85% in monkey M1 and 62% in monkey M2 were visually selective, 14% in monkey M1 and 4% in monkey M2 were face-selective and 8% in monkey M1 and 2% in monkey M2, were category-selective. To find out how these morphs are represented at the level of the population of all recorded neurons, we first reduced the dimensionality of the data applying the Principal Component Analysis (PCA) and using the best 10% of the principal components ranked according to the variance they explained. We used a pattern classifier (Support Vector Machine or SVM) to learn this new representation (form by the principal components) of the responses to human and monkey faces and classify the responses to ambiguous morphs into one of both categories. We found that in both cases (using the neural responses recorded in monkeys M1 and M2), and symmetric to the findings in humans, the classifier drew the category boundary closer to the monkey category (at approximately 40%human/60% monkey). These findings suggest an ‘own species’ advantage in the encoding of face stimuli by human and monkey observers. Our findings also indicate that this species-specific advantage is represented by a large fraction of neurons in the inferior temporal (IT) cortex of the monkey brain.},
web_url = {http://frontiersin.org/conferences/individual_abstract_listing.php?conferid=2&pap=418&ind_abs=1&pg=1},
event_name = {1st INCF Congress of Neuroinformatics: Databasing and Modeling the Brain},
event_place = {Stockholm, Sweden},
state = {published},
DOI = {10.3389/conf.neuro.11.2008.01.102},
author = {Sigala RA{sigala}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ 5311,
title = {Novel Calcium Sensitive MRI Contrast Agent: A Potential Agent for in vivo testing},
year = {2008},
month = {9},
number = {1502},
abstract = {Ca2+ plays an important dual role as a carrier of electrical current and as a second messenger in the brain. Its effects are much more diverse than of other second messengers such as cAMP (3',5'-cyclic adenosine monophosphate) and DAG (Diacylglycerol) as its actions are mediated by large array of proteins including protein kinases. Optical imaging with the help of fluorescent dyes has revealed the important role played by Ca2+; however it is limited by depth penetration and photobleaching side product. Magnetic Resonance Imaging (MRI), owing to its noninvasive characteristics together with its high spatial and temporal resolution doesn’t possess such limitations. In order to exploit these characteristics of MRI, Li. et al. (JACS comm. 1999) have proposed a smart contrast agent based on the high affinity chelator BAPTA, showing sensitivity to Ca2+ concentration in the range of 0.1 to 10 µM with an apparent dissociation constant of 0.96 µM. Contrast agents with such a strong affinity Ca2+ chelator are likely to be saturated once the Ca2+ concentration exceeds 1µM. We report here the synthesis of a Ca2+ sensitive smart contrast agent based on a low affinity chelator APTRA (o-aminophenol-N,N,O-triacetate). The agent showed 100% relaxivity enhancement in presence of Ca2+. Besides its excellent sensitivity, the agent was found Ca2+ selective in the presence of Mg2+ and Zn2+. Its relaxivity response in physiological media such as artificial cerebro-spinal fluid (ACSF) and artificial extracellular matrix (AECM) was found to be 37 % and 27 % respectively. CSF is the fluid that occupies the subarachnoid space and ventricular system around and inside the brain while ECM materials are mostly present in intercellular spaces between neurons and glia. The observed relaxivity changes in these physiological media prove the prospects of the agent for in vivo tests.},
web_url = {http://www.abstractsonline.com/viewer/viewAbstract.asp?CKey={D8AE58D9-C2EA-4152-BA98-1137F8656F49}&MKey={B47BAE74-CCA9-4C27-80FB-0005AFC9E5C0}&AKey={A4C6DD8F-4BF2-400D-97ED-20C14381CDBB}&SKey={EB48FD2C-03BC-414B-8733-3C12AFA98531}},
event_name = {2008 World Molecular Imaging Congress (WMIC)},
event_place = {Nice, France},
state = {published},
author = {Dhingra K{kirti}{Department Physiology of Cognitive Processes}, Maier ME, Beyerlein M{bayo}{Department Physiology of Cognitive Processes}, Angelovski G{goran}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5258,
title = {Novel Gd-Based Neuroanatomical Tract Tracers for Optical and Magnetic Resonance Imaging},
year = {2008},
month = {9},
number = {1917},
abstract = {The advance of axonal tract-tracing has revolutionized neuroscience in the past three decades1. The elementary purpose of neuronal tract-tracing is to chart anatomical connections within the nervous system providing useful information on afferent and efferent connectivity in the brain. Biocytin is a classical neuroanatomical tract-tracer that is taken up by neurons and transported in both antero- and retrograde directions. Our aim was to develop non-toxic, efficient neuronal tracers that allow both, in vivo brain connectivity studies by means of MRI and postmortem-microscopic investigation in fixed tissue, in the same experimental animal.
We have designed five novel biocytin-based neuroanatomical tract-tracers (L1-L5). In newly modified-biocytin (L1), propylamine is linked to amide of biocytin to make it tert-amide, which is stable to biotinidase degradation. The propylamine of L1was used as a linker to link, FITC as a fluorescent moiety (L2) or Gd-DOTA as MR detectable part (L3). L4 has an amide linkage between amine of GdDO3A-EA and carboxylate of biocytin while L5 consists of a novel precursor based on serine containing Gd-DO3A. This precursor has an amine and a carboxylate group available for coupling of biotin and l-lysine.
In vivo histological experiments with L1 demonstrated an increased molecular stability compared with biocytin and excellent neuronal tract-tracing capabilities. In vitro efficiency of cell internalization of L2 into N18 neuroblastoma cells was demonstrated by fluorescence microscopy. In vitro MRI of L3-L5 with increasing concentrations of avidin were performed at 7T. The increase in R2 for L3-L5 (300%-100% respectively) demonstrated strong binding of all tracers in the pocket of tetrameric avidin through biotin.
The above studies and preliminary results reveal a new strategy for neuroanatomical tract-tracing, which combines the powerful spatial resolution of the conventional microscopic techniques with the whole brain tri-dimensional coverage and in vivo applicability of MRI.},
web_url = {http://www.abstractsonline.com/viewer/viewAbstract.asp?CKey={9BE99CAE-EE89-4877-B998-50CE3C202694}&MKey={B47BAE74-CCA9-4C27-80FB-0005AFC9E5C0}&AKey={A4C6DD8F-4BF2-400D-97ED-20C14381CDBB}&SKey={16320777-E163-45F2-A6CB-BA79432F62F0}},
event_name = {2008 World Molecular Imaging Congress (WMIC)},
event_place = {Nice, France},
state = {published},
author = {Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Dhingra K{kirti}{Department Physiology of Cognitive Processes}, Mishra R{ritu}, Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Canals S{canals}}
}

@Poster{ 5468,
title = {Smart MRI Agents Sensing Extracellular Calcium Fluctuations},
year = {2008},
month = {9},
number = {1938},
abstract = {Functional Magnetic Resonance Imaging (fMRI) is currently the main tool used for the study of function and dysfunction of the human brain. The current mainstay of fMRI, the so-called Blood-Oxygen-Level-Dependent (BOLD) contrast, capitalizes on the detection of changes in cerebral blood flow, volume and oxygenation, but cannot directly report neural activity, as it suffers from poor spatiotemporal resolution and specificity compared to the actual neural events. An alternative methodology could be that relying on the responsive, ‘smart’ contrast agents whose relaxivity depends on the concentration of substances directly related to neuronal activity.
Ca2+ is an excellent marker closely linked to brain activation and is preferred target for various imaging methods. We report two Gd3+ chelates linked to a modified EGTA moiety that have a relaxivity response to extracellular Ca2+ fluctuations in the brain. The proton relaxivity of both Gd3+ complexes is sensitive to the variation of Ca2+ concentration. They are selective to Ca2+ with respect to the main competitor cation Mg2+. Upon interaction with Ca2+, the complexes exhibit high and reversible relaxivity changes; the relaxivity response of one complex upon addition of Ca2+ exceeds 80%. Moreover, the relaxivity changes remain remarkable (>50%) even in the medium mimicking the brain extracellular fluid, exhibiting a ~10% relaxivity change in the physiologically relevant Ca2+ concentration range (changes induced during the neural activity).
These agents have great potential to be applied as functional MR markers and be used for the visualization of the neural processes. They can substantially increase the specificity and spatial resolution of the MR-detected signals and open new perspectives in fMRI.},
web_url = {http://www.abstractsonline.com/viewer/viewAbstract.asp?CKey={097A637B-5B8D-45E7-B130-C68B245FC717}&MKey={B47BAE74-CCA9-4C27-80FB-0005AFC9E5C0}&AKey={A4C6DD8F-4BF2-400D-97ED-20C14381CDBB}&SKey={16320777-E163-45F2-A6CB-BA79432F62F0}},
event_name = {2008 World Molecular Imaging Congress (WMIC)},
event_place = {Nice, France},
state = {published},
author = {Angelovski G{goran}{Department Physiology of Cognitive Processes}, Fouskov{\'a} P, Mamedov I{ilgar}{Department Physiology of Cognitive Processes}, Canals S{canals}, T{\'o}th {\'E} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5289,
title = {On the neural mechanisms of binocular rivalry},
journal = {Perception},
year = {2008},
month = {8},
volume = {37},
number = {ECVP Abstract Supplement},
pages = {128},
abstract = {We will discuss our attempts to study neural correlates of the perceptual alternations experienced upon viewing of ambiguous figures, and relate them to new psychophysical evidence offering a new twist in the eye-versus-percept debate. Our studies over the last decade indicated that perception-responsive cells are concentrated in cortical areas near the top of the processing hierarchy, but that they can be found all along the visual pathway. Similarly, psychophysics has shown that both, monocular as well as binocular, percept based neural representations contribute to perceptual dominance. Our new psychophysical evidence suggests a time-dependence of eye and percept contributions in binocular rivalry: initially a given monocular channel has greater influence on dominance, regardless of the percept. Over time, this reverses, with percept-related (ie eye-independent) processes increasingly 'urging' for a perceptual switch. We suggest this may reflect a single process, where monocular as well as binocular neural stages affect each other in a feedback-loop that evolves over time. Understanding rivalry thus calls for the study of networks rather than single neurons.},
web_url = {http://www.perceptionweb.com/abstract.cgi?id=v080459},
event_name = {31st European Conference on Visual Perception},
event_place = {Utrecht, Netherlands},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes} and Logothetis N{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ RemediosLK2008,
title = {Auditory representations in the insula cortex},
year = {2008},
month = {7},
volume = {6},
number = {188.21},
abstract = {Cortical auditory system organization comprises a number of responsive areas that span a region in the primate forebrain extending from the temporal lobe to the frontal lobe. These areas collaborate in structured networks where sensory information is distributed into several processing streams. In this context, human imaging studies provide preliminary evidence to suggest a role for the insula cortex in auditory processing, especially in processing speech and language. In this study we electrophysiologically characterize the primate insula cortex in terms of its auditory capabilities. To facilitate the interpretation of our findings, we systematically compare the response properties of insular neurons to those of neurons in the primary and secondary auditory cortices.
Our findings identify an acoustically responsive region in the posterior insula cortex that is activated by both simplistic as well as naturalistic sounds. Although these insular neurons exhibit response properties similar to neurons in auditory cortex such as responsiveness to simple stimuli and tuning to sound frequency, they also differ from auditory cortical neurons in that they express longer latencies and that they do not sensitively represent the sound envelope. Individual stimuli are encoded sparsely across the population of neurons within the insula, yet these neurons are more selective to particular natural sounds than auditory cortical neurons. Interestingly, primate insular neurons demonstrate a preference for conspecific vocalizations. Furthermore, we are also able to identify a differential response to different vocalization types. Our findings thus suggest a role for the insula cortex in processing and representing auditory information preferentially vocalizations.},
web_url = {http://fens2008.neurosciences.asso.fr/},
event_name = {6th Forum of European Neuroscience (FENS 2008)},
event_place = {Geneva, Switzerland},
state = {published},
author = {Remedios R{ryan}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Poster{ 5478,
title = {Cross-modal influences on information processing in auditory cortex},
year = {2008},
month = {7},
volume = {9},
number = {450},
pages = {114},
abstract = {Recent results from human imaging and electrophysiology promote the view that processing within auditory cortex can be influenced by crossmodal stimulation of other sensory modalities. Here we scrutinize the neuronal basis of these sensory interactions and ask whether they increase the information about the sensory environment available in neuronal responses. Recording field potentials and single unit responses in regions of the monkey auditory cortex we characterized the modulatory influence of visual stimuli on the responses to acoustic stimuli. While slow field
potentials showed widespread visual modulations, only few individual neurons exhibited significant multisensory interactions, such as response enhancement or suppression. The visual modulation occurred only for a narrow time window of stimulus onset asynchronies and was independent
of the particular kind of stimulus used. Using information theoretic analysis, we found that visual stimuli do not change the information in neuronal firing rates about the acoustic stimulus. However, visual modulation increased
the information available in slow field potentials and in the phase of firing of individual neurons. Our results let us conclude that cross-modal input enhances the information available in auditory cortex about the environment and that this information is available not in the response
strength of individual neurons but in a temporal neural code.},
web_url = {http://imrf.mcmaster.ca/IMRF/2008/pdf/FullProgramIMRF08.pdf},
event_name = {9th International Multisensory Research Forum (IMRF 2008)},
event_place = {Hamburg, Germany},
state = {published},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Poster{ 5148,
title = {Development of biocytin-based contrast agents for molecular imaging: an approach towards new in vivo neuroanatomical tracers},
year = {2008},
month = {7},
volume = {6},
number = {096.17},
abstract = {Biocytin is a widely used anterograde and retrograde neuroanatomical tracer. Due to its high affinity towards avidin, it can be visualized by using a host of avidin-conjugated markers at the electron microscopic level. Here we report the synthesis of the multimodal neuronal tracers that can be visualized by electron microscopy as well as by magnetic resonance imaging (MRI) in living animals, thus allowing longitudinal brain connectivity studies in vivo, followed by postmortem subcellular investigations.
We have designed and synthesized three novel and structurally different gadolinium (Gd3+) containing biocytin-based neuroanatomical tracers (L1-L3). L1 contained amide linkage between amine of GdDO3A-EA and carboxylate of biocytin. L2 consist of a novel precursor based on serine containing Gd-DO3A which has 1° amino group as well as a carboxylate group available for binding. 1° amino group has been used to form amide bond with acid group of biotin while its carboxylate group has been linked to alpha amino group of l-lysine via amide bond. Newly developed modified biocytin (MB) consisted of propylamine linked to the amide bond in biocytin. L3 is derived from newly developed MB where propylamine is linked to amide of biocytin giving the possibility to couple Gd-DOTA as MRI marker.
In vitro MR experiments with increasing concentrations of avidin were performed at 7T. The r2 for L1-L3 (300%, 80% and 100% respectively) demonstrated strong binding of all tracers in the pocket of tetrameric avidin through biotin. By replacing Gd-DOTA with FITC in L3, the efficiency of cell internalization was demonstrated microscopically with fluorescence methods. In vivo experiments with L3 demonstrated an increased molecular stability compared with regular biocytin and excellent neuronal tract-tracing capabilities.
Our results suggest that the class of biocytin-based and Gd-containing molecules described here, represents a new and powerful strategy for neuroanatomical.},
file_url = {/fileadmin/user_upload/files/publications/FENS_[0].pdf},
web_url = {http://fens2008.neurosciences.asso.fr/},
event_name = {6th Forum of European Neuroscience (FENS 2008)},
event_place = {Geneva, Switzerland},
state = {published},
author = {Mishra A{anuragrk}{Department Physiology of Cognitive Processes}, Sch\"uz A{schuez}{Department Physiology of Cognitive Processes}, Dhingra K{kirti}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Canals S{canals}}
}

@Poster{ CanalsBL2008,
title = {Functional magnetic resonance imaging (fMRI) of synaptic plasticity},
year = {2008},
month = {7},
volume = {6},
number = {079.4},
abstract = {Repetitive stimulation of hippocampal neurons induce a fast and prolonged increase in local synaptic strength, which is known as LTP (long-term potentiation). LTP is currently considered as being the cellular model of associative learning and memory. Despite the relevance of such phenomenon in the healthy and diseased brain, and all valuable information gained in the study of its cellular and molecular mechanisms, little is known about its role in whole-brain functional connectivity. The lack of a better understanding of the context-dependent network organization most likely reflects the fact that most current methodologies are not really suited for the study of mass action. In an attempt to overcome this limitation, we previously combined electrophysiological techniques and electrical microstimulation of the rat perforant path with functional magnetic resonance imaging (fMRI) (Canals et al. 2008, in press) and showed that the fMRI signal (BOLD) in this model is a good surrogate of the neuronal activity as measured electrophysiologically. Here, we investigate the functional patterns produced as a result of long-term potentiation of synaptic transmission in the rat hippocampus. FMRI maps of the entire brain were obtained before, during and after the induction of LTP, demonstrating changes in functional connectivity due to synaptic potentiation. Furthermore, our results demonstrate that the magnitude of the potentiation is heterogeneously distributed across different hippocampal areas, and that interhemispheric communication is also potentiated after LTP induction. The present model (BOLD-LTP) represents the first demonstration of synaptic plasticity using fMRI and will allow us to further study the information transfer between the hippocampus, the cerebral cortex and subcortical structures, providing new data for the understanding of memory and learning processes.},
web_url = {http://fens2008.neurosciences.asso.fr/},
event_name = {6th Forum of European Neuroscience (FENS 2008)},
event_place = {Geneva, Switzerland},
state = {published},
author = {Canals S{canals}, Beyerlein M{bayo}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5887,
title = {How visual context influences the acoustical processing in and around auditory cortex},
year = {2008},
month = {7},
volume = {6},
number = {020.10},
abstract = {Recent results from human imaging and electrophysiological studies promote the view that processing within auditory cortex can be influenced by cross-modal stimulation of other sensory modalities. Here we scrutinize the neuronal basis of these sensory interactions by probing regions in the monkey auditory pathway for multisensory influences using combinations of functional imaging (fMRI) and electrophysiology.
Using functional imaging, we previously found that caudal fields of the auditory cortex show enhanced fMRI-BOLD responses when auditory stimuli were complemented by simultaneous visual or touch stimulation [see Kayser et al. Neuron 48, 2005 and J. Neurosci. 27(8), 2007]. This sensory interaction was much enhanced in the superior temporal regions but was less evident in anterior auditory fields and the insula. To validate these results at the level of individual neurons, we now record field potentials and single unit activity from these regions. We find that within caudal auditory cortex, only 12% of the neurons show cross-modal influences, such as response enhancement or suppression. This visual modulation occurs only for a narrow time window of stimulus onset asynchronies and is independent of the particular kind of stimulus used. In the acoustically responsive region of the insula a similar proportion of neurons show such kind of audio-visual interaction, while in the superior temporal region visual, auditory and multisensory neurons are spatially intermingled and occur in equal proportions.
Our findings reveal how the presence of visual input increases along the auditory processing stream and demonstrate that already early auditory cortices are susceptible to cross-modal influences. As a consequence we conclude that the processing at these stages not only reflects acoustical stimuli but is also dependent on their visual context.},
web_url = {http://fens2008.neurosciences.asso.fr/},
event_name = {6th Forum of European Neuroscience (FENS 2008)},
event_place = {Geneva, Switzerland},
state = {published},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Petkov C{chrisp}, Remedios R{ryan}{Research Group Physiology of Sensory Integration}, Dahl CD{dahl}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ SimanovaCEL2008,
title = {Imaging of learning-associated brain activity in freely behaving rats using manganese-enhanced MRI (MEMRI)},
year = {2008},
month = {7},
volume = {6},
number = {225.21},
abstract = {MEMRI was applied for mapping brain activity in rats subjected to spatial learning. MnCl2 was used as a T1-shortening contrast agent that increases the signal intensity at the locations where Mn2+ ions accumulate. Mn2+ enter the cells via voltage-gated calcium channels and its accumulation in the brain is proportional to neural activity. Rats were implanted (IP) with Mn-loaded osmotic pumps (0.5mmol/kg/200microL) that provided a constant and slow release of Mn (1microL/h) over 14 days, and they were subjected to three experimental conditions. The first group was trained to perform a T-maze delayed alternation task. During the sample trial the two maze arms (start and reward) were available and the side of reward location varied randomly across ten daily trials. During the choice trial all three maze arms were open and the reward was available on the alternative maze arm only. There was a 30-sec delay between the sample and the choice trials. On average, after 10 days of training, the rats reached an asymptotic performance with 90% correct choices. Two other groups of rats served as controls. Sedentary rats were kept in the home cage for the entire duration of training. Pseudo-trained rats were subjected to the identical procedure on the maze except for the alternation rule. Rats received the reward regardless of their choice of a particular maze arm. After 14 days all rats were scanned in 7T magnet under isoflurane anesthesia. Statistical maps of the functional brain activation were generated from group paired comparisons using t-test. Exposure to the maze resulted in elevated accumulation of Mn2+ in hippocampus. Rats, trained to perform the alternation task, showed additional activation of primary sensory areas (visual, auditory, and somatosensory). MEMRI allowed visualizing learning-related brain activity in freely behaving animals. This technique can be used for tracking the dynamic reorganization of neural networks at multiple time points in the same animal.},
web_url = {http://fens2008.neurosciences.asso.fr/},
event_name = {6th Forum of European Neuroscience (FENS 2008)},
event_place = {Geneva, Switzerland},
state = {published},
author = {Simanova I, Canals S{canals}, Eschenko O{oeschenko}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5336,
title = {Investigating the relationship between pharmacological MRI and electrophysiology using Canonical Correlation Analysis},
year = {2008},
month = {7},
volume = {6},
number = {123.3},
abstract = {Pharmacological MRI (phMRI) is a rapidly advancing field whose goal it is to map the modulatory effects of pharmacological agents on the large-scale brain networks that underlie cognition. However, the relation between these effects on functional imaging signals and the underlying neural activity is unclear. We have combined phMRI with electrophysiological recordings of neural activity to link effects at the level of imaging signals to those observed in electrical recordings from neuronal populations. During fMRI acquisition, we recorded the broad-band comprehensive neuronal signal, and extract from it time courses of four relevant frequency bands: low (1-12Hz), medium (12-24Hz) gamma (24-90) and multi-unit-activity (400-3000Hz). At the same time we registered BOLD activity in a region of interest around the electrode tip, placed in the primary visual cortex. Scans were about 40 minutes long, during which we delivered a visual stimulus for periods of 30 seconds followed by blank periods of equal length. During visual stimulation we then locally applied either an inhibitory neurotransmitter (GABA), an excitatory neuromodulator (ACh) or just saline solution. We used a recently proposed algorithm for performing Canonical Correlation Analysis (CCA) between fMRI data and electrophysiological activity. Preliminary results show, that CCA robustly finds dependencies between groups of voxels in the fMRI data and frequency bands in the electrophysiological data. For example, a component dominated by the MUA signal was associated with voxels that tended to cluster near the injector and showed inhibitory effects for GABA injection and excitatory effects for ACh injection. These findings suggest that CCA is a promising candidate for revealing relations between neural activity and the fMRI signal during pharmacological manipulations.},
web_url = {http://fens2008.neurosciences.asso.fr/},
event_name = {6th Forum of European Neuroscience (FENS 2008)},
event_place = {Geneva, Switzerland},
state = {published},
author = {Biessmann F{fbiessma}{Department Physiology of Cognitive Processes}, Rauch A{arauch}{Department Physiology of Cognitive Processes}, Meinecke F, Zhang X{xiaozhe}{Department Physiology of Cognitive Processes}, Rainer G{gregor}, M\"uller K-R{klaus} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ MackeBEOTB2008,
title = {Modeling populations of spiking neurons with the Dichotomized Gaussian distribution},
year = {2008},
month = {7},
web_url = {http://www.theswartzfoundation.org/summer-meeting-2008.asp},
event_name = {Annual Meeting 2008 of Sloan-Swartz Centers for Theoretical Neurobiology},
event_place = {Princeton, NJ, USA},
state = {published},
author = {Macke JH{jakob}, Berens P{berens}{Research Group Computational Vision and Neuroscience}, Ecker AS{aecker}{Research Group Computational Vision and Neuroscience}, Opper M, Tolias AS{atolias}{Department Physiology of Cognitive Processes} and Bethge M{mbethge}{Research Group Computational Vision and Neuroscience}}
}

@Poster{ 5443,
title = {Neurophysiological substrates of visual awareness in the macaque prefrontal cortex},
year = {2008},
month = {7},
volume = {6},
number = {220.12},
abstract = {Human fMRI studies during binocular rivalry have demonstrated an involvement of prefrontal cortex (PFC) in the processing of subjective visual perception. In this study we used binocular flash suppression, a version of binocular rivalry that permits the robust induction of a visual percept, to study the neuronal correlates of visual awareness in the macaque prefrontal cortex (PFC) and specifically in the inferior prefrontal convexity. We found that the firing rate of almost 70% of the visually selective neurons closely followed the induced visual percept. This percentage is significantly higher than the respective percentage of perceptually modulated cells found in the striate and extrastriate visual cortex (V1, V2 and V4) but smaller than that found in the inferior temporal cortex (IT) (almost 90%). Interestingly, we observed that the neuronal responses following a perceptual alternation were transient, similar to the transient BOLD response observed during perceptual transitions in the human binocular rivalry fMRI studies. Our finding provides further evidence in support of a role of higher brain areas in processing an explicit perceptual representation during ambiguous visual stimulation. In addition, it points to a potential neuronal network consisting of perceptually modulated cells in IT and PFC that process an explicit representation of a visual percept. The existence of such a network is not surprising since area TE of inferior temporal cortex is anatomically connected to the inferior convexity (areas 12/45) through feedforward and feedback pathways.
Finally, in an effort to explore whether the perceptual modulation observed in primary visual cortex (V1) is influenced by a feedback signal from PFC we will also present data from simultaneous PFC and V1 neurophysiological recordings during binocular flash suppression.},
web_url = {http://fens2008.neurosciences.asso.fr/},
event_name = {6th Forum of European Neuroscience (FENS 2008)},
event_place = {Geneva, Switzerland},
state = {published},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Tolias A{atolias}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ RauchZRL2008,
title = {Quantifying the impact of serotonin on brain function using pharmacological MRI and electrophysiology in the non-human primate},
year = {2008},
month = {7},
volume = {6},
number = {018.20},
abstract = {Serotonin is one of the major neuromodulators with a broad range of pharmacological actions and has been implicated in several neurological disorders including schizophrenia. Here we investigate neuronal and metabolic effects induced by the local application of serotonin receptor 1A agonist BP554 in cortex of the non-human primate. We focused on the primary visual cortex, allowing us to robustly induce activation using the presentation of a visual stimulus. We performed electrical recordings of neural activity in conjunction with simultaneous monitoring of the blood oxygenation level dependent (BOLD) signal before, during and after the local application of BP554. Neural activity was analyzed both at the level of the local field potential (LFP) and multi unit activity (MUA). We performed a total of 17 experiments in three subjects. Our main finding was that BOLD activity was largely unaffected by the injection of BP554 (no significant changes in activity, t-test, P = 0.64). Similarly, the application had little effect on LFP activity (no significant changes in activity, t-test, P = 0.56). By contrast, MUA was robustly reduced following the injection of BP554. (Reduction of activity by 34%, t-test, P < 0.05). Because LFP as well as BOLD activity are largely related to synaptic activity, our findings suggest that BP554 had little effect on the average level of local processing. The output of the local network, as estimated by MUA activity, is by contrast strongly affected by BP554. This suggests that serotonin may leave local information processing intact, but block the results of the local computations from being transmitted to other brain regions. This network behaviour may contribute to disorders associated with serotonin dysfunction.},
web_url = {http://fens2008.neurosciences.asso.fr/},
event_name = {6th Forum of European Neuroscience (FENS 2008)},
event_place = {Geneva, Switzerland},
state = {published},
author = {Rauch A{arauch}{Department Physiology of Cognitive Processes}, Zhang X{xiaozhe}{Department Physiology of Cognitive Processes}, Rainer G{gregor} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5481,
title = {Sensory interactions in the claustrum and insula cortex},
year = {2008},
month = {7},
volume = {9},
number = {307},
pages = {271},
abstract = {Once considered to be components of the same structure, the claustrum and the overlying insula cortex are intricately connected to several sensory areas and are therefore presumptive sites for multisensory integration. We test this hypothesis using a combination of visual and acoustical stimuli while recording from the claustrum and insula cortex of awake non-human primates.
Our study revealed that the claustrum was parcellated into sensory zones, one of which was predominantly acoustical while another was predominantly visual. However, within each of these zones, we were not only able to identify neurons that responded to the other modality, but also identify some neurons that were multimodal. Within the posterior insula cortex, on the other hand, sensory representations were preferentially acoustical in nature, and although a third of the neurons were in fact modulated by visual activity, only a fraction of these were actually responsive to both modalities. Using natural sounds we uncovered an insular preference towards conspecific vocalizations wherein neurons here could distinguish between vocalizations themselves, based on the sound’s temporal character.
Our findings suggest that although various sensory modalities may converge onto a structure, modality dominant zones can still exist within, with multisensory neurons intermingled among them.},
web_url = {http://imrf.mcmaster.ca/IMRF/2008/pdf/FullProgramIMRF08.pdf},
event_name = {9th International Multisensory Research Forum (IMRF 2008)},
event_place = {Hamburg, Germany},
state = {published},
author = {Remedios R{ryan}{Research Group Physiology of Sensory Integration}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Poster{ 6170,
title = {Systematic Investigation of Vascular Corrosion Casts of the Macaque Monkey Brain},
year = {2008},
month = {7},
volume = {6},
number = {130.8},
abstract = {Introduction: In the past, the structural properties of the cerebral microvasculature have been analyzed using a wide range of anatomical methods, each revealing differential aspects of this system. Here, we used the corrosion cast technique to characterize the arrangement and organization of the blood vessels and the ratio of arteries and veins in different parts of the macaque’s brain.
Methods: Following standard perfusion with saline, two adult monkeys (Macaca nemestrina) were injected with Batson’s #17 resin. After polymerization the brains were extracted, deep-frozen and serial 5 mm thick slabs were cut coronally or horizontally with a dedicated tissue knife. The cut surface was matched with the monkey brain atlas (Saleem, 2006). The slabs were then macerated using 5% KOH until all tissue was removed, frozen in distilled water and trimmed with a sliding microtome to obtain an even surface. After complete drying, anatomical areas were identified and cut from the slabs, sputter coated with gold and imaged with the use of a scanning electron microscope.
Results: The general vascular organization was found to be very similar to that of the human brain as described by Duvernoy (1981). The same classes of vessels (depending on penetration depth and branching points) could be identified. The mean ratio of cortical arteries and veins was found to be 1: ~1.6, with arteries being the more numerous vessel type. The average irrigation volume of a large penetrating artery was estimated to be 0.44 mm*, whereas the draining volume of a large cortical vein was found to be 0.70 mm*. Different subcortical regions (e. g. LGN) could be identified solely on the basis of the arrangement of blood vessels that clearly followed the shape of the structure.
Discussion: The applied method allows for a qualitative description of the general organization principles of the brain’s vasculature, as well as for the estimation of the ratio between arterial and venous vessels.},
file_url = {/fileadmin/user_upload/files/publications/fens2008_[0].pdf},
web_url = {http://fens2008.neurosciences.asso.fr/},
event_name = {6th Forum of European Neuroscience (FENS 2008)},
event_place = {Geneva, Switzerland},
state = {published},
author = {Keller AL{akeller}{Department Physiology of Cognitive Processes}, Weber B{bweber} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5288,
title = {The coding of colour, motion and their conjunction revisited using fMRI pattern classifier analysis},
year = {2008},
month = {7},
event_name = {Asia-Pacific Conference on Vision (APCV 2008)},
event_place = {Brisbane, Australia},
state = {published},
author = {Seymour K{seymour}{Department Physiology of Cognitive Processes}, Clifford C, Logothetis N{nikos}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5511,
title = {The Role of Primary Visual Cortex (V1) in Perceptual Suppression},
year = {2008},
month = {7},
volume = {6},
number = {220.8},
abstract = {When two incongruent stimuli are presented simultaneously at corresponding retinal locations in the two eyes, one typically experiences a perceptual alternation of the two stimuli; a phenomenon known as binocular rivalry. Binocular flash suppression (BFS) is a variant of binocular rivalry and refers to the sudden and persistent perceptual suppression resulting when two rivalrous patterns are presented dichoptically and asynchronously to the two eyes. Under these conditions, the latter pattern dominates perceptually over the first. The binocular flash suppression paradigm ensures excellent control over the subject’s perceptual state without the need for subjective reports which involve decision making, action preparation and action execution. The role of primary visual cortex (V1) in perceptual suppression remains controversial. In this study, we assessed quantitatively the effects of perceptual suppression on neural activity in V1 of the macaque using BFS. We have analyzed both the spiking activity of a large number of single neurons (SUA) and different frequency bands of the local field potentials (LFPs). The main result for SUA was that only a small minority (~20%) modulates in consonance with the perceptual suppression of static orientation gratings. Furthermore, the magnitude of the perceptual effect was small (~15%) in comparison to the sensory preference of the neurons. LFPs showed comparable percentages. The amplitude of LFP modulations was independent of frequency although gamma frequencies showed greater selectivity during physical alternation of the stimuli. Our results provide evidence against the hypothesis that competition is happening at the level of monocular neurons at the input layers of primary visual cortex.},
web_url = {http://fens2008.neurosciences.asso.fr/},
event_name = {6th Forum of European Neuroscience (FENS 2008)},
event_place = {Geneva, Switzerland},
state = {published},
author = {Keliris GA{george}{Department Physiology of Cognitive Processes}, Tolias AS{atolias}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5857,
title = {Analysis of Pattern Recognition Methods in Classifying Bold Signals in Monkeys at 7-Tesla},
year = {2008},
month = {6},
pages = {67},
abstract = {Pattern recognition methods have shown that fMRI data can reveal significant information
about brain activity. For example, in the debate of how object-categories are represented in
the brain, multivariate analysis has been used to provide evidence of distributed encoding
schemes. Many follow-up studies have employed different methods to analyze human fMRI
data with varying degrees of success. In this study we compare four popular pattern recognition
methods: correlation analysis, support-vector machines (SVM), linear discriminant analysis
and Gaussian naïve Bayes (GNB), using data collected at high field (7T) with higher resolution
than usual fMRI studies. We investigate prediction performance on single trials and for averages
across varying numbers of stimulus presentations. The performance of the various algorithms
depends on the nature of the brain activity being categorized: for several tasks,
many of the methods work well, whereas for others, no methods perform above chance level.
An important factor in overall classification performance is careful preprocessing of the data,
including dimensionality reduction, voxel selection, and outlier elimination.},
web_url = {http://www.areadne.org/2008/home.html},
event_name = {AREADNE 2008: Research in Encoding and Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Ku S-P{shihpi}{Department Physiology of Cognitive Processes}, Gretton A{arthur}{Department Empirical Inference}, Macke J{jakob}{Department Empirical Inference}, Tolias AT{atolias}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5860,
title = {Imaging the Oxygen Extraction Fraction with fMRI Using Moderate Hypercapnia},
year = {2008},
month = {6},
pages = {104},
web_url = {http://www.areadne.org/2008/home.html},
event_name = {AREADNE 2008: Research in Encoding and Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Zappe A-C{aczappe}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5859,
title = {Prediction od Behavioral Choice and Reaction Time from Local Field Potential in Macaque Prefrontal Cortex},
year = {2008},
month = {6},
pages = {70},
web_url = {http://www.areadne.org/2008/home.html},
event_name = {AREADNE 2008: Research in Encoding and Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Liebe S{sliebe}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Poster{ 5442,
title = {Single units reflect visual awareness in the macaque prefrontal cortex},
year = {2008},
month = {6},
pages = {80},
web_url = {http://www.areadne.org/2008/home.html},
event_name = {AREADNE 2008: Research in Encoding and Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Panagiotaropoulos T{theofanis}{Department Physiology of Cognitive Processes}, Kapoor V{vishal}{Department Physiology of Cognitive Processes}, Keliris GA{george}{Department Physiology of Cognitive Processes}, Tolias A{atolias}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5287,
title = {The coding of colour, motion and their conjunction revisited using fMRI pattern classifier analysis},
journal = {NeuroImage},
year = {2008},
month = {6},
volume = {41},
number = {Supplement 1},
pages = {S147},
event_name = {14th Annual Meeting of the Organisation for Human Brain Mapping (HBM 2008)},
event_place = {Melbourne, Australia},
state = {published},
author = {Seymour K{seymour}{Department Physiology of Cognitive Processes}, Clifford C, Logothetis N{nikos}{Department Physiology of Cognitive Processes} and Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5510,
title = {The Role of Primary Visual Cortex in Perceptual Awareness},
year = {2008},
month = {6},
pages = {61},
abstract = {Under certain stimulus conditions a single interpretation of the external world cannot be
unambiguously designated. When the brain is presented with such stimuli typically only one
possible interpretation is perceived and after a few seconds the percept switches abruptly to
another. Notably such perceptual alternations happen while the sensory input is kept
constant, offering thus a clear dissociation of sensory stimulation and subjective awareness.
A celebrated example of such a perceptual phenomenon is binocular rivalry (BR). It involves
alternations of visual perception between two different images presented dichoptically at corresponding
retinal locations. Based on many psychophysical studies over decades the primary
visual cortex (V1) was implicated as an important candidate for the site of perceptual suppression.
However, the first neurophysiological evidence performed in monkeys did not corroborate
this but instead found only a small percentage of neurons modulating their activity with
the subjective awareness reported by the animals. On the contrary, studies using human functional
magnetic resonance imaging (fMRI), have found V1 to be modulating to a large extent,
creating an apparent controversy. Therefore, the role of primary visual cortex (V1) in subjective
perception remains controversial.
In this study, we studied the effects of perceptual suppression on neural activity in V1 of the
macaque. We have used the binocular flash suppression (BFS) paradigm, a variant of BR
which ensures excellent control over the subject’s perceptual state. We have recorded the
spiking activity of a large number of well isolated single units (SUA) and acquired simultaneous
local field potentials (LFPs) during the dichoptic presentation of orthogonal orientation
gratings. Our design enabled us to determine a) which neurons and LFP bands are correlated
with the percept and b) how this is related to their orientation and ocularity preferences.
We find that only a small minority of about 20% of the single units modulate in consonance
with the perceptual suppression. Furthermore, the magnitude of the perceptual effect was
small (~15%) in comparison to the sensory preference of the neurons. Results of the LFPs
were very similar to the single units showing a similar percentage of sites modulating with
perception. Analysis of the orientation and ocularity preference of neurons did not show a particular
class of cells to be having a greater probability to show perceptual modulations.},
web_url = {http://www.areadne.org/2008/home.html},
event_name = {AREADNE 2008: Research in Encoding and Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Keliris GA{george}{Department Physiology of Cognitive Processes}, Tolias AS{atolias}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 6183,
title = {The sparseness of stimulus encoding by single neurons and by populations of neurons in the inferior temporal cortex},
year = {2008},
month = {6},
pages = {42},
abstract = {low stimulus selectivity with a sparseness of 1.0 indicating a neuron that is non-selective to
the set of stimuli. The sparseness of the encoding of stimuli by single neurons and by populations
of neurons is fundamental to understanding the efficiency and capacity of representations
in the brain.
The sparseness of the responses of single neurons in the primate inferior temporal visual cortex
(the single neuron sparseness as) was measured to a set of 20 visual stimuli including
objects and faces in macaques performing a visual fixation task. Neurons included for analysis
had significant firing rate increases from baseline in response to some of the stimuli. The firing
rate distribution of 36% of the neurons was exponential. Twenty-nine percent of the neurons
had too few low rates to be fitted by an exponential distribution, and were fitted by a gamma
distribution. The sparseness as of the representation of the set of 20 stimuli provided by each
of these neurons had an average across all neurons of 0.77, indicating a rather distributed
representation.
The sparseness of the representation of a given stimulus by the whole population of neurons
(the population sparseness ap) also had an average value of 0.77. Ergodicity is the ability to
predict the distribution of the responses of the system at any one time (the population level)
from the distribution of the responses of a component of the system across time. Considering
this in neuronal terms, for the average sparseness of a population of neurons over multiple
stimulus inputs to be ergodic, it must equal the average sparseness to the stimuli of the single
neurons within the population, provided that the responses of the neurons are uncorrelated
(Foldiak 2003). As there is little or no correlation in the response profiles of inferior temporal
cortex neurons (Rolls et al, 2004), the similarity of the average single neuron sparseness as
and population sparseness for any one stimulus taken at any one time ap shows that the neural
representation of visual stimuli such as objects and faces is essentially ergodic.},
file_url = {/fileadmin/user_upload/files/publications/Abstract%20C32%20AREADNE2008_[0].pdf},
web_url = {http://www.areadne.org/2008/home.html},
event_name = {AREADNE 2008: Research in Encoding and Decoding of Neural Ensembles},
event_place = {Santorini, Greece},
state = {published},
author = {Aggelopoulos NC{aggelopoulos}{Department Physiology of Cognitive Processes}, Franco L, Jerez JM and Rolls ET}
}

@Poster{ HaroonMKALP2008,
title = {Comparing Corticocortical Interconnection Information from Tracer Studies and Probabilistic Tractography in the Postmortem Macaque Brain},
year = {2008},
month = {5},
volume = {16},
number = {3369},
pages = {543},
abstract = {We present a study attempting to validate the corticocortical connection information obtainable from diffusion-weighted MR data. We have implemented
probabilistic tractography in data acquired in a macaque model and compared this with connection information in a database of invasive tracer studies in the same model. The nature of the corticocortical interconnection information gained from probabilistic tractography is different to that gained from invasive studies, the latter also being sparse. Our results using the LVE00a parcellation scheme indicate that probabilistic tractography is able to give statistically comparable information on corticocortical interconnections to invasive tracer studies.},
file_url = {fileadmin/user_upload/files/publications/ISMRM-2008-03369.pdf},
web_url = {http://www.ismrm.org/08/},
event_name = {16th Scientific Meeting and Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM 2008)},
event_place = {Toronto, Canada},
state = {published},
author = {Haroon HA, Morris DM, Kaiser A{akaiser}{Department Physiology of Cognitive Processes}, Augath M{mark}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Parker GJM}
}

@Poster{ ZappeUL2008,
title = {Negative BOLD Signal Under 6% Hypercapnia Reflects Solely Oxygen Extraction from the Blood},
year = {2008},
month = {5},
volume = {16},
number = {850},
pages = {166},
abstract = {The BOLD signal is sensitive to cerebral blood flow (CBF), blood volume (CBV) and oxygen extraction. In the anesthetized monkey, we observe a vasodilatory ceiling effect during inhalation of 6% CO2 where CBF or CBV are not further increased by visual stimulation. In contrast, simultaneously measured local field potential responds to the stimulation as strong as during normocapnia. As a consequence, the stimulus-induced fMRI response during
6% hypercapnia has been found to be negative reflecting only the oxygen extraction from the blood. With this method, oxygen extraction can be imaged by means of fMRI without injection of an exogenous drug.},
file_url = {fileadmin/user_upload/files/publications/ISMRM-2008-00850.pdf},
web_url = {http://www.ismrm.org/08/},
event_name = {16th Scientific Meeting and Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM 2008)},
event_place = {Toronto, Canada},
state = {published},
author = {Zappe A-C{aczappe}{Department Physiology of Cognitive Processes}, Uludag K{kuludag} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5485,
title = {Positive and negative BOLD-signals from blood vessels in monkey visual cortex},
year = {2008},
month = {5},
volume = {16},
number = {153},
pages = {27},
abstract = {High-resolution fMRI can aid in determining to what extent the BOLD signal arises from capillaries or larger vessels. In high-resolution functional activation maps both positive and negative BOLD signals associated with vessels were observed; this was seen for both GE- and SE-BOLD. Because of its higher specificity, the SE-BOLD signal was used to investigate the origin of these vessel signals. The location of the SE-BOLD signal from veins changed when the direction of the gradients was changed. This is in contrast to the peak SE-BOLD occurring in layer IV which arises from capillaries, and was insensitive to gradient reversal.},
file_url = {fileadmin/user_upload/files/publications/ISMRM-2008-00153.pdf},
web_url = {http://www.ismrm.org/08/},
event_name = {16th Scientific Meeting and Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM 2008)},
event_place = {Toronto, Canada},
state = {published},
author = {Goense JBM{jozien}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5130,
title = {Whose voice is that? In pursuit of an animal model of vocal recognition},
year = {2008},
month = {4},
web_url = {http://www.ccg.unam.mx/en/news/days_molecular_medicine_2008},
event_name = {Days of Molecular Medicine 2008},
event_place = {Stockholm, Sweden},
state = {published},
author = {Petkov C{chrisp}, Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}, Patterson R, Ghazanfar AA{asifg}{Department Physiology of Cognitive Processes} and Logothetis N{nikos}{Department Physiology of Cognitive Processes}}
}

@Poster{ 5512,
title = {Binocular Flash Suppression in area V1 of the macaque},
year = {2008},
month = {2},
event_name = {First Annual inter-Science of Learning Center (iSLC): Student and Postdoc Conference},
event_place = {Pittsburgh, PA, USA},
state = {published},
author = {Keliris GA{george}{Department Physiology of Cognitive Processes}, Tolias AS{atolias}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Thesis{ 5260,
title = {Analysis of neural signals: Interdependence, information coding, and relation to network models},
year = {2008},
month = {6},
day = {3},
file_url = {/fileadmin/user_upload/files/publications/RASCH_thesis_5260[0].pdf},
state = {published},
type = {PhD},
author = {Rasch MJ{rasch}{Department Physiology of Cognitive Processes}}
}

@Thesis{ 4948,
title = {Design, Synthesis and Characterization of Novel Exogenous Smart/Bioresponsive Contrast Agents for Magnetic Resonance and Optical Imaging},
year = {2008},
month = {1},
day = {1},
abstract = {Magnetic Resonance Imaging (MRI) is a valuable and versatile technique for
visualizing internal structures first described in 19781. It is an extension of Nuclear
Magnetic Resonance (NMR) spectroscopy used in chemistry. Molecular imaging
using magnetic resonance techniques is a rapidly growing field in diagnostic medicine
and basic neuroscience. The high spatial resolution and the undisputed capacity of
differentiating soft tissues have highly contributed to the widespread use of this
imaging modality. MRI offers the potential of realistic three dimensional imaging of
biological structures, where the signal is based upon the resonance of water protons.
With the advent of improved variety of technologies both in terms of
hardware/software and the versatile techniques, it is possible to obtain detailed
anatomical, physiological and metabolic/functional information with carefully
designed experiments, which could address various intriguing questions concerning
neural mechanisms of cognitive functions in the primate, which is the thrust area of
our research.},
state = {published},
type = {PhD},
author = {Mishra A{anuragrk}{Department Physiology of Cognitive Processes}}
}

@Conference{ 5623,
title = {Colour, motion, connectivity and natural vision in the primate brain},
year = {2008},
month = {12},
day = {19},
event_name = {Neurocolloquium},
event_place = {Zürich, Switzerland},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ 5769,
title = {Colour, motion and natural vision in the primate brain},
year = {2008},
month = {12},
day = {18},
web_url = {http://www.cin.uni-tuebingen.de/events/past-events/2008-events.php},
event_name = {Junior Research Group Selection Symposium 5: Werner Reichardt Centre for Integrative Neuroscience},
event_place = {Tübingen, Germany},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ 5622,
title = {fMRI of the primate brain: functional mapping, connectivity, and motion processing},
year = {2008},
month = {12},
day = {15},
event_name = {Neurowissenschaftliches Kolloquium},
event_place = {Mannheim, Germany},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ KuGML2008,
title = {Pattern recognition methods in classifying fMRI data},
year = {2008},
month = {10},
volume = {9},
number = {11},
abstract = {Pattern recognition methods have shown that fMRI data can reveal signicant information
about brain activity. For example, in the debate of how object{categories are represented
in the brain, multivariate analysis has been used to provide evidence of a distributed
encoding scheme. Many follow{up studies have employed dierent methods to analyze
human fMRI data with varying degrees of success. In this presentation I would like
to discuss and compare four popular pattern recognition methods: correlation analysis,
support{vector machines (SVM), linear discriminant analysis and Gaussian nave Bayes
(GNB), using data collected at high eld (7T) with higher resolution than usual fMRI
studies. We investigate prediction performance on single trials and for averages across
varying numbers of stimulus presentations. The performance of the various algorithms
depends on the nature of the brain activity being categorized: for several tasks, many of
the methods work well, whereas for others, no methods perform above chance level. An
important factor in overall classication performance is careful preprocessing of the data,
including dimensionality reduction, voxel selection, and outlier elimination.},
web_url = {http://www.neuroschool-tuebingen-nena.de/index.php?id=284},
event_name = {9th Conference of the Junior Neuroscientists of Tübingen (NeNa 2008)},
event_place = {Ellwangen, Germany},
state = {published},
author = {Ku S-P{shipi}, Gretton A{arthur}{Department Empirical Inference}, Macke J{jakob}{Department Empirical Inference} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

@Conference{ RauchMBMLR2008,
title = {The effect of a serotonine agonist on neural activity and BOLD activity in monkey primary visual cortex, a pharmacological fMRI (PhMRI) study},
journal = {Frontiers in Computational Neuroscience},
year = {2008},
month = {10},
volume = {Conference Abstract: Bernstein Symposium 2008},
abstract = {Functional magnetic resonance imaging (fMRI) offers great diagnostic potential for monitoring brain activity due to its non-invasiveness. However the neurophysiological basis of BOLD contrast mechanisms in fMRI is not fully understood. Pharmacological functional magnetic resonance imaging (PhMRI) is a promising new direction in biomedical imaging, which allows for monitoring drug related effects on brain processes. When using drugs with known pharmacodynamics (drug effects on the brain), PhMRI offers great possibilities to get a better understanding of the neuronal basis of the BOLD signal. It can provide the link between drug induced biomolecular changes and their corresponding BOLD response. To take full advantage of PhMRI we are developing an integrated software and hardware platform to record in real-time mode simultaneously neurophysiological and BOLD signals to follow drug induced changes in both signals. Real-time mode allows for controlling drug induced effects tightly and offers the possibility to online modify application parameters of the drug. We started to test pharmacological agents and investigated the effect of the neuromodulator BP554 in the primary visual cortex (V1), of anesthetized monkeys. BP554 is a 5-HT1A agonist acting primarily on the membrane of efferent neurons by potassium-induced hyperpolarization. Combined electrophysiology and (fMRI) experiments suggested that local field activity (LFP) is a better predictor of the BOLD signal than multi-unit activity (MUA). This is particularly true because BOLD responses remain undiminished in cases where spiking might be entirely absent despite clear, strong stimulus-induced modulation of the field potentials. To further test this hypothesis we induced the dissociation of MUA from LFP activity with injections of BP554 into primary visual cortex. Neuroimaging was performed in a 4.7 Tesla Scanner (Bruker, Germany). Recorded were spiking activity and local field potentials. V1 was stimulated by rotating polar checkerboard stimulus (blocks by 30 sec stimulus, 30 sec blank, 37 repetitions). 300 microm to the recording electrode we injected BP554 (100 microM solution). The infusion of BP554 in visual cortex reliably reduced MUA without affecting LFP and BOLD activity. This finding suggests that the efferents of a neuronal network pose little metabolic burden compared to the overall pre- and postsynaptic processing of incoming afferents. These results show how powerful PhMRI can be in approaching the still open issue of the coupling between neuronal activity and the BOLD signal, when appropriate hardware and software achievements are incorporated.},
web_url = {http://www.frontiersin.org/10.3389/conf.neuro.10.2008.01.013/event_abstract},
event_name = {Bernstein Symposium 2008},
event_place = {München, Germany},
state = {published},
DOI = {10.3389/conf.neuro.10.2008.01.013},
author = {Rauch A{arauch}{Department Physiology of Cognitive Processes}, Meinec FC, Biessmann F{fbiessma}{Department Physiology of Cognitive Processes}, M\"uller K-R{klaus}{Department Empirical Inference}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Rainer G{gregor}}
}

@Conference{ 5291,
title = {Natural vision in the primate brain: functional mapping, connectivity, and motion processing},
year = {2008},
month = {9},
day = {16},
web_url = {http://nguyendangbinh.org/Proceedings/FG08/proceedings/content/workshops.htm},
event_name = {Workshop on Psychology of Face and Gesture Recognition},
event_place = {Amsterdam, Netherlands},
state = {published},
author = {Bartels A{abartels}{Department Physiology of Cognitive Processes}}
}

@Conference{ 5290,
title = {On the neural mechanisms of binocular rivalry},
journal = {Frontiers in Human Neuroscience},
year = {2008},
month = {9},
day = {4},
volume = {Conference Abstract: 10th International Conference on Cognitive Neuroscience},
abstract = {Binocular rivalry is scientifically attractive because it allows the study of an entirely subjective experience using objective measurements: During rivalry the visual percept changes dramatically – from one image to another – while the two stimuli presented to the eyes remain constant. There are at least two aspects whose neural origin would be worthwhile understanding: 1. The mechanisms that lead to the stochastic, spontaneous, and sometimes abrupt alternations of the percept from one stimulus to the other; 2. The mechanisms that keep one stimulus dominant, perceived, and the other suppressed. Previous psychophysical studies have elegantly demonstrated that both monocular and binocular sites contribute to perceptual alternations and to perceptual dominance. Recordings from single neurons, from monocular cells in V1 to cells in the prefrontal cortex show signals representing both the suppressed as well as the dominant stimuli. The proportion of neurons exhibiting percept-modulated responses rises from V1, through V4/V5, IT to prefrontal cortex. Additionally, some studies have reported that certain bands of local field potentials in V1 contain more information about the percept than spikes, while fMRI results in the human brain even show perceptual modulations in the LGN. Like psychophysics, physiology points toward a potentially complex interaction of several neural sites involved in rivalry. We will present the latest recordings from hundreds of neurons in V1, as well as initial recordings from prefrontal cortex. We will mainly focus however, on new psychophysical results shedding light on the eye-versus-percept debate. These results suggest a time-dependence of eye and percept contributions in binocular rivalry. During a dominance period, it appears that it is initially a given monocular channel that has major influence on dominance, regardless of the percept. Over time, this reverses, with image-related, eye-independent processes increasingly controlling any perceptual switch. Our results lead us to suggest that monocular effects – as observed here and in previous studies – may directly depend on higher-level effects and vice versa, because monocular as well as higher-level perceptual influences on dominance vary in parallel but with opposite signs over time. Therefore, the monocular and binocular effects observed in binocular rivalry may reflect different ends of a single process affecting several neural stages. A potential model could be that an initially strong stimulus representation is stabilized by a reinforcing, noise-reducing loop between binocular and monocular stages. As the stability of this process weakens, both the monocular channel loses influence, and the binocular stimulus representation weakens, increasingly favoring a perceptual switch.},
web_url = {http://www.frontiersin.or