% % This file was created by the Typo3 extension % sevenpack version 0.7.14 % % --- Timezone: CEST % Creation date: 2017-05-23 % Creation time: 12-50-06 % --- Number of references % 116 % @Article { AzadbakhtPHALdDP2015, title = {Validation of High-Resolution Tractography Against In Vivo Tracing in the Macaque Visual Cortex}, journal = {Cerebral Cortex}, year = {2015}, month = {11}, volume = {25}, number = {11}, pages = {4299-4309}, abstract = {Diffusion magnetic resonance imaging (MRI) allows for the noninvasive in vivo examination of anatomical connections in the human brain, which has an important role in understanding brain function. Validation of this technique is vital, but has proved difficult due to the lack of an adequate gold standard. In this work, the macaque visual system was used as a model as an extensive body of literature of in vivo and postmortem tracer studies has established a detailed understanding of the underlying connections. We performed probabilistic tractography on high angular resolution diffusion imaging data of 2 ex vivo, in vitro macaque brains. Comparisons were made between identified connections at different thresholds of probabilistic connection “strength,” and with various tracking optimization strategies previously proposed in the literature, and known connections from the detailed visual system wiring map described by Felleman and Van Essen (1991; FVE91). On average, 74\% of connections that were identified by FVE91 were reproduced by performing the most successfully optimized probabilistic diffusion MRI tractography. Further comparison with the results of a more recent tracer study (Markov et al. 2012) suggests that the fidelity of tractography in estimating the presence or absence of interareal connections may be greater than this.}, department = {Department Logothetis}, web_url = {http://cercor.oxfordjournals.org/content/25/11/4299.full.pdf+html}, DOI = {10.1093/cercor/bhu326}, author = {Azadbakht, H and Parkes, LM and Haroon, HA and Augath, M and Logothetis, NK and de Crespigny, E and D'Arceuil, HE and Parker, GJM} } @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.}, department = {Department Logothetis}, web_url = {http://www.nature.com/nature/journal/v491/n7425/full/nature11618.html}, DOI = {10.1038/nature11618}, author = {Logothetis, NK and Eschenko, O and Murayama, Y and Augath, M and Steudel, T and Evrard, HC and Besserve, M and Oeltermann, A} } @Article { SultanAHMORT2017, title = {Unravelling cerebellar pathways with high temporal precision targeting motor and extensive sensory and parietal networks}, journal = {Nature Communications}, year = {2012}, month = {6}, volume = {3}, number = {924}, pages = {1-10}, abstract = {Increasing evidence has implicated the cerebellum in providing forward models of motor plants predicting the sensory consequences of actions. Assuming that cerebellar input to the cerebral cortex contributes to the cerebro-cortical processing by adding forward model signals, we would expect to find projections emphasising motor and sensory cortical areas. However, this expectation is only partially met by studies of cerebello–cerebral connections. Here we show that by electrically stimulating the cerebellar output and imaging responses with functional magnetic resonance imaging, evoked blood oxygen level-dependant activity is observed not only in the classical cerebellar projection target, the primary motor cortex, but also in a number of additional areas in insular, parietal and occipital cortex, including sensory cortical representations. Further probing of the responses reveals a projection system that has been optimized to mediate fast and temporarily precise information. In conclusion, both the topography of the stimulation effects and its emphasis on temporal precision are in full accordance with the concept of cerebellar forward model information modulating cerebro-cortical processing.}, department = {Department Logothetis}, web_url = {http://www.nature.com/articles/ncomms1912.pdf}, DOI = {10.1038/ncomms1912}, author = {Sultan, F and Augath, M and Hamodeh, S and Murayama, Y and Oeltermann, A and Rauch, A and Thier, P} } @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.}, department = {Department Logothetis}, 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}, DOI = {10.1016/j.mri.2011.08.002}, author = {Murayama, Y and Augath, M and Logothetis, NK} } @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.}, department = {Department Logothetis}, web_url = {http://cercor.oxfordjournals.org/cgi/reprint/bhq058v1}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1093/cercor/bhq058}, author = {Itturia-Medina, Y and Fernandez, AP and Morris, DM and Canales-Rodriguez, EJ and Haroon, HA and Penton, LG and Augath, M and Garcia, LG and Logothetis, NK and Parker, GJM and Melie-Garcia, L} } @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 \(\gamma\) 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.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science?_ob=MImg\&_imagekey=B6T9D-4Y6T7WF-2-C\&_cdi=5112\&_user=29041\&_pii=S0730725X09003087\&_orig=search\&_coverDate=01\%2F21\%2F2010\&_sk=999999999\&view=c\&wchp}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.mri.2009.12.016}, author = {Murayama, Y and Biessmann, F and Meinecke, FC and M{\"u}ller, K-R and Augath, M and Oeltermann, A and Logothetis, NK} } @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.}, department = {Department Logothetis}, web_url = {http://www.nature.com/neuro/journal/v13/n10/pdf/nn.2631.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1038/nn.2631}, author = {Logothetis, NK and Augath, M and Murayama, Y and Rauch, A and Sultan, F and Goense, J and Oeltermann, A and Merkle, H} } @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.}, department = {Department Logothetis}, web_url = {http://onlinelibrary.wiley.com/doi/10.1002/nbm.1500/pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1002/nbm.1500}, author = {Kirsch, S and Augath, M and Seiffge, D and Schilling, L and Schad, LR} } @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.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/Petkov\%20-\%20Sparse\%20vs\%20Continuous\%20MRI\%20-\%20MRI\%20-\%2009_5826[0].pdf}, department = {Department Logothetis}, department2 = {Research Group Kayser}, 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=}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.mri.2009.01.018}, author = {Petkov, CI and Kayser, C and Augath, M and Logothetis, NK} } @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.}, department = {Department Logothetis}, 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}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.jmr.2009.05.005}, author = {Augath, M and Heiler, P and Kirsch, S and Schad, LR} } @Article { 5874, title = {How not to study spontaneous activity}, journal = {NeuroImage}, year = {2009}, month = {5}, volume = {45}, number = {4}, pages = {1080-1089}, department = {Department Logothetis}, 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=}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.neuroimage.2009.01.010}, author = {Logothetis, NK and Murayama, Y and Augath, M and Steffen, T and Werner, J and Oeltermann, A} } @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 \verb=~=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.}, department = {Department Logothetis}, web_url = {http://www.plosone.org/article/fetchObjectAttachment.action;jsessionid=0A5232F6405DC5F1482FC1AB5827A3AD?uri=info\%3Adoi\%2F10.1371\%2Fjournal.pone.0005527\&representation=PDF}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1371/journal.pone.0005527}, EPUB = {e5527}, author = {Schmid, MC and Panagiotaropoulos, T and Augath, MA and Logothetis, NK and Smirnakis, SM} } @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.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/Wade-2008-jov-8-10-6_5684[0].pdf}, department = {Department Logothetis}, web_url = {http://journalofvision.org/8/10/6/Wade-2008-jov-8-10-6.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1167/8.10.6}, author = {Wade, A and Augath, M and Logothetis, NK and Wandell, B} } @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.}, department = {Department Logothetis}, 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}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.neuroimage.2007.12.009}, author = {Rauch, A and Rainer, G and Augath, M and Oeltermann, A and Logothetis, NK} } @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;lsquo;voice\&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.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/Petkov\%20-\%20Voice\%20Area\%20-\%20NatureNeuro\%20-\%202008_4896[0].pdf}, department = {Department Logothetis}, department2 = {Research Group Kayser}, web_url = {http://www.nature.com/neuro/journal/v11/n3/pdf/nn2043.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1038/nn2043}, author = {Petkov, CI and Kayser, C and Steudel, T and Whittingstall, K and Augath, M and Logothetis, NK} } @Article { 5723, title = {BOLD sensitivity to cortical activation induced by microstimulation: comparison to visual stimulation}, journal = {Magnetic Resonance Imaging}, year = {2007}, month = {7}, volume = {25}, number = {6}, pages = {754-759}, abstract = {Electrical microstimulation via intracortical electrodes is a widely used method for deducing functions of the brain. In this study, we compared the spatial extent and amplitude of BOLD responses evoked by intracortical electrical stimulation in primary visual cortex with BOLD activations evoked by visual stimulation. The experiments were performed in anesthetized rhesus monkeys. Visual stimulation yielded activities larger than predicted from the well-established visual magnification factor. However, electrical microstimulation yielded an even greater spread of the BOLD response. Our results confirm that the effects of electrical microstimulation extend beyond the brain region expected to be excited by direct current spread.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science/article/pii/S0730725X07002111}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.mri.2007.03.014}, author = {Sultan, F and Augath, M and Logothetis, NK} } @Article { 4670, title = {Simultaneous recording of neuronal signals and functional NMR imaging}, journal = {Magnetic Resonance Imaging}, year = {2007}, month = {7}, volume = {25}, number = {6}, pages = {760-774}, abstract = {We recently directly examined the relationship between blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signals and neural activity by simultaneously acquiring electrophysiological and fMRI data from monkeys in a 4.7-T vertical scanner (Logothetis NK, Pauls J, Augath MA, Trinath T, Oeltermann A. Neurophysiological investigation of the basis of the fMRI signal. Nature 2001;412:150–157). Acquisition of electrical signals in the microvolt range required extensive development of new recording hardware, including electrodes, microdrives, signal conditioning and interference compensation devices. Here, we provide a detailed description of the interference compensation system that can be used to record field and action potentials intracortically within a high-field scanner.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science?_ob=MImg\&_imagekey=B6T9D-4NMV01F-1-1\&_cdi=5112\&_user=29041\&_orig=browse\&_coverDate=07\%2F31\%2F2007\&_sk=999749993\&view=c\&wchp=dGLbVtb-zSkWz\&md5=ac3178304240a357f9979f7e804047a4\&ie=/sdarticle.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.mri.2007.03.015}, author = {Oeltermann, A and Augath, MA and Logothetis, NK} } @Article { 4282, title = {Functional imaging reveals visual modulation of specific fields in auditory cortex}, journal = {Journal of Neuroscience}, year = {2007}, month = {2}, volume = {27}, number = {8}, pages = {1824-1835}, abstract = {Merging information from different senses is essential for successfully interacting with real world situations. Indeed, sensory integration can reduce perceptual ambiguity, speed reactions or change the qualitative sensory experience. It is widely held that integration occurs at later processing stages and mostly in higher association cortices. However, recent studies suggest that sensory convergence can already occur in primary sensory cortex. A good model for early convergence proved to be the auditory cortex, which can be modulated by visual and tactile stimulation. However, given the large number and small size of auditory fields, neither microelectrode recordings, nor human imaging have systematically identified which fields are susceptible to multisensory influences. To reconcile findings from human imaging with anatomical knowledge from non-human primates, we exploited high-resolution imaging (fMRI) of the macaque monkey to study the modulation of auditory processing by visual stimulation. Using a func tional parcellation of auditory cortex, we localized modulations to individual fields. Our results demonstrate that both primary (core) and non-primary auditory fields (belt) can be activated by mere presentation of visual scenes. Audio-visual convergence was restricted to caudal fields (prominently core field: A1, and belt fields CM, CL and MM) and continued in the auditory parabelt and the superior temporal sulcus. The same fields exhibited enhancement of auditory activation by visual stimulation and showed stronger enhancement for less effective stimuli, two characteristics of sensory integration. Altogether, these findings reveal multisensory modulation of auditory processing prominently in caudal fields but also at the lowest stages of auditory cortical processing.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/Kayser_JNeurosci_07_4282[0].pdf}, department = {Department Logothetis}, web_url = {http://www.jneurosci.org/cgi/reprint/27/8/1824}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1523/JNEUROSCI.4737-06.2007}, author = {Kayser, C and Petkov, CI and Augath, M and Logothetis, NK} } @Article { 3827, title = {Spatial specificity of BOLD versus cerebral blood volume fMRI for mapping cortical organization}, journal = {Journal of Cerebral Blood Flow and Metabolism}, year = {2007}, month = {1}, volume = {27}, number = {6}, pages = {1248-1261}, abstract = {Intravascular contrast agents are used in functional magnetic resonance imaging to obtain cerebral blood volume (CBV) maps of cortical activity. Cerebral blood volume imaging with MION (monocrystalline-iron-oxide-nanoparticles) increases the sensitivity of functional imaging compared with the blood oxygenation level-dependent (BOLD) signal (Leite et al, 2002; Mandeville et al, 1998; Vanduffel et al, 2001). It therefore represents an attractive method for obtaining detailed maps of cortical organization (Vanduffel et al, 2001; Zhao et al, 2005). However, it remains to be determined how the spatial profile of CBV maps of cortical activity derived with MION compares with the profile of BOLD activation maps under a variety of different stimulation conditions. We used several stimulation paradigms to compare the spatial specificity of CBV versus BOLD activation maps in macaque area V1 at 4.7 T. We observed that: (1) CBV modulation is relatively stronger in deep cortical layers compared with BOLD, in agreement with studies in cats (Harel et al, 2006) and rodents (Lu et al, 2004; Mandeville and Marota, 1999) and (2) surprisingly, under large surround stimulation conditions, CBV maps extend along the cortical surface to cover large (\&gt;10 mm) regions of the cortex that are devoid of significant BOLD modulation. We conclude that the spatial profiles of BOLD and CBV activity maps do not coregister across all stimulus conditions, and therefore do not necessarily represent equivalent transforms of the neural response. Cerebral blood volume maps should be interpreted with care, in the context of the particular experimental paradigm applied.}, department = {Department Logothetis}, web_url = {http://www.nature.com/jcbfm/journal/v27/n6/pdf/9600434a.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1038/sj.jcbfm.9600434}, author = {Smirnakis, SM and Schmid, MC and Weber, B and Tolias, AS and Augath, M and Logothetis, NK} } @Article { 3967, title = {Functional Imaging Reveals Numerous Fields in the Monkey Auditory Cortex}, journal = {PLoS Biology}, year = {2006}, month = {7}, volume = {4}, number = {7}, pages = {1213-1226}, abstract = {Anatomical studies propose that the primate auditory cortex contains more fields than have actually been functionally confirmed or described. Spatially resolved functional magnetic resonance imaging (fMRI) with carefully designed acoustical stimulation could be ideally suited to extend our understanding of the processing within these fields. However, after numerous experiments in humans, many auditory fields remain poorly characterized. Imaging the macaque monkey is of particular interest as these species have a richer set of anatomical and neurophysiological data to clarify the source of the imaged activity. We functionally mapped the auditory cortex of behaving and of anesthetized macaque monkeys with high resolution fMRI. By optimizing our imaging and stimulation procedures, we obtained robust activity throughout auditory cortex using tonal and band-passed noise sounds. Then, by varying the frequency content of the sounds, spatially specific activity patterns were observed over this region. As a result, the activity patterns could be assigned to many auditory cortical fields, including those whose functional properties were previously undescribed. The results provide an extensive functional tessellation of the macaque auditory cortex and suggest that 11 fields contain neurons tuned for the frequency of sounds. This study provides functional support for a model where three fields in primary auditory cortex are surrounded by eight neighboring “belt” fields in non-primary auditory cortex. The findings can now guide neurophysiological recordings in the monkey to expand our understanding of the processing within these fields. Additionally, this work will improve fMRI investigations of the human auditory cortex.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/Petkov_PLOS_06_3967[0].pdf}, department = {Department Logothetis}, web_url = {http://biology.plosjournals.org/archive/1545-7885/4/7/pdf/10.1371_journal.pbio.0040215-S.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1371/journal.pbio.0040215}, EPUB = {e215}, author = {Petkov, C and Kayser, C and Augath, M and Logothetis, N} } @Article { 3987, title = {Development of visually evoked cortical activity in infant macaque monkeys studied longitudinally with fMRI}, journal = {Magnetic Resonance Imaging}, year = {2006}, month = {3}, volume = {24}, number = {4}, pages = {359-366}, abstract = {We studied the development of visual activation longitudinally in two infant monkeys aged 103–561 days using the BOLD fMRI technique under opiate anesthesia and compared the results with those obtained in three adult animals studied under identical conditions. Visual activation in primary visual cortex, V1, was strong and reliable in monkeys of the youngest and oldest ages, showing that functional imaging techniques give qualitatively similar results in infants and adults. Visual activation in extrastriate areas involved in processing motion (MT/V5) and form (V4) was not evident in the younger animals, but became more adult-like in the older animals. This delayed onset of measurable BOLD responses in extrastriate visual cortex may reflect delayed development of visual responses in these areas, although at this stage it is not possible to rule out either effects of anesthesia or of changes in cerebral vascular response mechanisms as the cause. The demonstration of visually evoked BOLD responses in young monkeys shows that the BOLD fMRI technique can usefully be employed to address functional questions of brain development.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science?_ob=MImg\&_imagekey=B6T9D-4JFHF31-2-K\&_cdi=5112\&_user=29041\&_orig=browse\&_coverDate=05\%2F31\%2F2006\&_sk=999759995\&view=c\&wchp=dGLbVtz-zSkzS\&md5=cf0082d56e93d81632c0262821036d50\&ie=/sdarticle.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.mri.2005.12.025}, author = {Kourtzi, Z and Augath, M and Logothetis, NK and Movshon, A and Kiorpes, L} } @Article { 3922, title = {Negative functional MRI response correlates with decreases in neuronal activity in monkey visual area V1}, journal = {Nature Neuroscience}, year = {2006}, month = {3}, volume = {9}, number = {4}, pages = {569-577}, abstract = {Most functional brain imaging studies use task-induced hemodynamic responses to infer underlying changes in neuronal activity. In addition to increases in cerebral blood flow and blood oxygenation level–dependent (BOLD) signals, sustained negative responses are pervasive in functional imaging. The origin of negative responses and their relationship to neural activity remain poorly understood. Through simultaneous functional magnetic resonance imaging and electrophysiological recording, we demonstrate a negative BOLD response (NBR) beyond the stimulated regions of visual cortex, associated with local decreases in neuronal activity below spontaneous activity, detected 7.15 +- 3.14 mm away from the closest positively responding region in V1. Trial-by-trial amplitude fluctuations revealed tight coupling between the NBR and neuronal activity decreases. The NBR was associated with comparable decreases in local field potentials and multiunit activity. Our findings indicate that a significant component of the NBR or iginates in neuronal activity decreases.}, department = {Department Logothetis}, web_url = {http://www.nature.com/neuro/journal/v9/n4/pdf/nn1675.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1038/nn1675}, author = {Shmuel, A and Augath, M and Oeltermann, A and Logothetis, NK} } @Article { 3986, title = {Tracing neural circuits in vivo with Mn-enhanced MRI}, journal = {Magnetic Resonance Imaging}, year = {2006}, month = {3}, volume = {24}, number = {4}, pages = {349-358}, abstract = {The application of MRI-visible paramagnetic tracers to reveal in vivo connectivity can provide important subject-specific information for multisite, multielectrode intracortical recordings in combined behavioral and physiology experiments. To establish the use of such tracers in the nonhuman primate, we recently compared the specificity of the anterograde tracer Mn2+ with that of wheat-germ-agglutinin conjugated to horseradish peroxidase (WGA-HRP) in experiments tracing the neuronal connections of the basal ganglia of the monkey. It was shown that Mn2+ and WGA-HRP yield the same projection patterns and that the former tracer crosses at least two synapses, for it could be found in thalamus following injections into the striatum. Here we provide evidence that Mn2+ reaches the cortex following striatum injections and, thus, is transferred even further than previously shown. In other words, used as a paramagnetic MRI tracer, Mn2+ can permit the visualization of neural networks covering at least four processing st ages. Moreover, unilateral intravitreal injections show that Mn2+ is sufficiently synapse specific to permit visualization of the lamina of the dorsal lateral geniculate nucleus (dLGN). Interestingly, the transfer rate of the substance reflected the well-known axonal size differences between the parvocellular and magnocellular layers of dLGN. After intravitreal injections, we were able to demonstrate transfer of Mn2+ into several subcortical and cortical areas, including the inferotemporal cortex. The specificity of the transsynaptic transfer of manganese that we report here indicates the value of this tracer for chronic studies of development and plasticity, as well as for studies of brain pathology.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science?_ob=MImg\&_imagekey=B6T9D-4JHMRYV-2-C\&_cdi=5112\&_user=29041\&_orig=browse\&_coverDate=05\%2F31\%2F2006\&_sk=999759995\&view=c\&wchp=dGLbVzb-zSkWW\&md5=90b5c081dc0a86b8f124af1027602bb5\&ie=}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.mri.2005.12.031}, author = {Murayama, Y and Weber, B and Kadharbatcha, SS and Augath, M and Logothetis, NK} } @Article { 4479, title = {Mapping Cortical Activity Elicited with Electrical Microstimulation Using fMRI in the Macaque}, journal = {Neuron}, year = {2005}, month = {12}, volume = {48}, number = {6}, pages = {901-911}, abstract = {Over the last two centuries, electrical microstimulation has been used to demonstrate causal links between neural activity and specific behaviors and cognitive functions. However, to establish these links it is imperative to characterize the cortical activity patterns that are elicited by stimulation locally around the electrode and in other functionally connected areas. We have developed a technique to record brain activity using the blood oxygen level dependent (BOLD) signal while applying electrical microstimulation to the primate brain. We find that the spread of activity around the electrode tip in macaque area V1 was larger than expected from calculations based on passive spread of current and therefore may reflect functional spread by way of horizontal connections. Consistent with this functional transynaptic spread we also obtained activation in expected projection sites in extrastriate visual areas, demonstrating the utility of our technique in uncovering in vivo functional connectivity maps.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science?_ob=MImg\&_imagekey=B6WSS-4HVMT2J-7-2\&_cdi=7054\&_user=29041\&_orig=browse\&_coverDate=12\%2F22\%2F2005\&_sk=999519993\&view=c\&wchp=dGLbVzb-zSkWz\&md5=72ecd52a491258a743a50f885045465e\&ie=/sdarticle.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.neuron.2005.11.034}, author = {Tolias, AS and Sultan, F and Augath, MA and Oeltermann, A and Tehovnik, EJ and Schiller, PH and Logothetis, NK} } @Article { 3726, title = {Neuroscience: Rewiring the adult brain (Reply)}, journal = {Nature}, year = {2005}, month = {11}, volume = {438}, number = {7065}, pages = {E3-E4}, abstract = {We disagree with Calford et al. that there is a consensus on adult plasticity in primate V1 cortex: for example, macaque area V1 cytochrome oxidase levels remained depressed for several months after binocular retinal lesions; no reorganization in macaque V1 after monocular retinal lesions was found; and no area V1 reorganization in a patient with macular degeneration was detected.}, department = {Department Logothetis}, web_url = {http://www.nature.com/nature/journal/v438/n7065/abs/nature04360.html}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1038/nature04360}, author = {Smirnakis, SM and Schmid, MC and Brewer, AA and Tolias, AS and Sch{\"u}z, A and Augath, MA and Inhoffen, W and Wandell, BA and Logothetis, NK} } @Article { 3533, title = {Integration of touch and sound in auditory cortex}, journal = {Neuron}, year = {2005}, month = {10}, volume = {48}, number = {2}, pages = {373-384}, abstract = {To form a coherent percept of the environment, our brain combines information from different senses. Such multisensory integration occurs in higher association cortices; but supposedly it also occurs in early sensory areas. Confirming the latter hypothesis, we unequivocally demonstrate supra-additive integration of touch and sound stimulation at the second stage of the auditory cortex. Using high-resolution fMRI of the macaque monkey, we quantified the integration of auditory broad-band noise and tactile stimulation of hand and foot in anaesthetized animals. Integration was found posterior to and along the lateral side of the primary auditory cortex in the caudal auditory belt. Integration was stronger for temporally coincident stimuli and obeyed the principle of inverse effectiveness: greater enhancement for less effective stimuli. These findings demonstrates that multisensory integration occurs early and close to primary sensory areas, and \&amp;amp;amp;\#8211; as it occurs in anaesthet ized ani mals //! --MFG_und--//amp;\#8211; suggests that this integration is mediated by pre-attentive bottom-up mechanisms.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/Kayser_Neuron_05_3533[0].pdf}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science?_ob=MImg\&_imagekey=B6WSS-4HC6GJV-V-3\&_cdi=7054\&_user=29041\&_orig=search\&_coverDate=10\%2F20\%2F2005\&_sk=999519997\&view=c\&wchp=dGLbVlz-zSkzV\&md5=2d8adb856c014d50807f6b8898864236\&ie=/sdarticle.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/j.neuron.2005.09.018}, author = {Kayser, C and Petkov, CI and Augath, M and Logothetis, NK} } @Article { 3325, title = {Lack of long-term cortical reorganization after macaque retinal lesions}, journal = {Nature}, year = {2005}, month = {5}, volume = {435}, number = {7040}, pages = {300-307}, abstract = {Several aspects of cortical organization are thought to remain plastic into adulthood, allowing cortical sensorimotor maps to be modified continuously by experience. This dynamic nature of cortical circuitry is important for learning, as well as for repair after injury to the nervous system. Electrophysiology studies suggest that adult macaque primary visual cortex (V1) undergoes large-scale reorganization within a few months after retinal lesioning, but this issue has not been conclusively settled. Here we applied the technique of functional magnetic resonance imaging (fMRI) to detect changes in the cortical topography of macaque area V1 after binocular retinal lesions. fMRI allows non-invasive, in vivo, long-term monitoring of cortical activity with a wide field of view, sampling signals from multiple neurons per unit cortical area. We show that, in contrast with previous studies, adult macaque V1 does not approach normal responsivity during 7.5 months of follow-up after retinal lesions, and its topography does not change. Electrophysiology experiments corroborated the fMRI results. This indicates that adult macaque V1 has limited potential for reorganization in the months following retinal injury.}, department = {Department Logothetis}, web_url = {http://www.nature.com/nature/journal/v435/n7040/abs/nature03495.html;jsessionid=2A77D316DEC3A65D47341EF03D079D49}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1038/nature03495}, author = {Smirnakis, SM and Brewer, AA and Schmid, MC and Tolias, AS and Sch{\"u}z, A and Augath, M and Inhoffen, W and Wandell, BA and Logothetis, NK} } @Article { 2067, title = {Integration of Local Features into Global Shapes: Monkey and Human fMRI Studies}, journal = {Neuron}, year = {2003}, month = {1}, volume = {37}, number = {2}, pages = {333-346}, abstract = {The integration of local image features into global shapes was investigated in monkeys and humans using fMRI. An adaptation paradigm was used, in which stimulus selectivity was deduced by changes in the course of adaptation of a pattern of randomly oriented elements. Accordingly, we observed stronger activity when orientation changes in the adapting stimulus resulted in a collinear contour than a different random pattern. This selectivity to collinear contours was observed not only in higher visual areas that are implicated in shape processing, but also in early visual areas where selectivity depended on the receptive field size. These findings suggest that unified shape perception in both monkeys and humans involves multiple visual areas that may integrate local elements to global shapes at different spatial scales.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/pdf2067.pdf}, department = {Department B{\"u}lthoff}, department2 = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science?_ob=MImg\&_imagekey=B6WSS-47STJPB-K-H\&_cdi=7054\&_user=29041\&_orig=browse\&_coverDate=01\%2F23\%2F2003\&_sk=999629997\&view=c\&wchp=dGLbVlz-zSkzS\&md5=456e08b25ca9888e6292a3139f0e3102\&ie=/sdarticle.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, DOI = {10.1016/S0896-6273(02)01174-1}, author = {Kourtzi, Z and Tolias, AS and Altmann, CF and Augath, M and Logothetis, NK} } @Article { 849, title = {The Effect of image scrambling on visual cortical BOLD activity in the anesthetized monkey}, journal = {Neuroimage}, year = {2002}, month = {7}, volume = {16}, number = {3A}, pages = {607-616}, abstract = {We have investigated BOLD signal changes associated with scrambling natural images into different numbers of segments in visually modulated regions of the macaque monkey (macacca mulatta) brain. For 10\(^{\circ}\) \(\times\) 10\(^{\circ}\) images, we observed that BOLDactivity in primary visual cortex (V1) increased with scrambling, and then dramatically dropped for very highly scrambled images (128 \(\times\) 128 segments). In extrastriate visual areas, BOLD signal levels did not distinguish between natural images and scrambled images, except that as in V1 very highly scrambled images led to a drop in BOLDactivity. Finally in the superior temporal sulcus region and inferior temporal cortex, BOLDactivity decreased systematically with scrambling. Our results are consistent with the view that the BOLD signal might reflect average activation of local orienation detectors in V1, and sensitivity to more global object representations in higher visual areas. In addition, we quantify the effects of scrambling on the Fourier amplitude spectrum of the images. This analysis shows that scrambling causes substantial changes to the spatial frequency content of images. This suggests that low-level accounts for reduced BOLD activation in higher visual areas cannot be completely ruled out based on scrambling data.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science/article/pii/S1053811902910864}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, DOI = {10.1006/nimg.2002.1086}, author = {Rainer, G and Augath, M and Trinath, T and Logothetis, NK} } @Article { 924, title = {Ultra High-Resolution fMRI in Monkeys with Implanted RF Coils}, journal = {Neuron}, year = {2002}, month = {7}, volume = {35}, number = {2}, pages = {227-242}, abstract = {Spatiotemporally resolved functional MRI (fMRI) in animals can reveal how wide-spread neural networks are organized and accompanying electrophysiological recordings can show how small neural assemblies contribute to this organization. Here we present a novel technique that yields high-resolution structural and functional images of the monkey brain with small, tissue-compatible, intraosteally implantable radiofrequency coils. Voxel sizes as small as 0.0113 \(\mu\)l with high signal-to-noise and contrast-to-noise ratios were obtained, revealing both structural and functional cortical architecture in great detail. Up to a certain point, contrast sensitivity increased with decreasing voxel size, probably because of the decreased partial volume effects. Spatial specificity was demonstrated by the lamina-specific activation in experiments comparing responses to moving and flickering stimuli. The implications of this technique for combined fMRI/electrophysiology experiments and its limitations in terms of spatial coverage are discussed.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science/article/pii/S0896627302007754}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, DOI = {10.1016/S0896-6273(02)00775-4}, author = {Logothetis, NK and Merkle, H and Augath, MA and Trinath, T and Ugurbil, K} } @Article { 926, title = {Magnetic Resonance Imaging of Neuronal Connections in the Macaque Monkey}, journal = {Neuron}, year = {2002}, month = {5}, volume = {34}, number = {5}, pages = {685-700}, abstract = {Recently, an MRI-detectable, neuronal tract-tracing method in living animals was introduced that exploits the anterograde transport of manganese (Mn2+). We present the results of experiments simultaneously tracing manganese chloride and wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) to evaluate the specificity of the former by tracing the neuronalconnections of the basal ganglia of the monkey. Mn2+ and WGA-HRP yielded remarkably similar and highly specific projection patterns. By showing the sequential transport of Mn2+ from striatum to pallidum-substantia nigra and then to thalamus, we demonstrated MRI visualization of transport across at least one synapse in the CNS of the primate. Transsynaptic tract tracing in living primates will allow chronic studies of development and plasticity and provide valuable anatomical information for fMRI and electrophysiological experiments in primates.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science/article/pii/S0896627302007183}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, DOI = {10.1016/S0896-6273(02)00718-3}, author = {Saleem, KS and Pauls, J and Augath, MA and Trinath, T and Prause, BA and Hashikawa, T and Logothetis, NK} } @Article { 852, title = {Three-Dimensional Shape Representation in Monkey Cortex.}, journal = {Neuron}, year = {2002}, month = {2}, volume = {33}, number = {4}, pages = {635-652}, abstract = {Using fMRI in anesthetized monkeys, this study investigates how the primate visual system constructs representations of three-dimensional (3D) shape from a variety of cues. Computer-generated 3D objects defined by shading, random dots, texture elements, or silhouettes were presented either statically or dynamically (rotating). Results suggest that 3D shaperepresentations are highly localized, although widely distributed, in occipital, temporal, parietal, and frontal cortices and may involve common brain regions regardless of shape cue. This distributed network of areas cuts across both “what” and “where” processing streams, reflecting multiple uses for 3D shaperepresentation in perception, recognition, and action.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science/article/pii/S0896627302005986}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, DOI = {10.1016/S0896-6273(02)00598-6}, author = {Sereno, M and Trinath, T and Augath, MA and Logothetis, NK} } @Article { 53, title = {Motion Processing in the Macaque: Revisited with Functional Magnetic Resonance Imaging}, journal = {Journal of Neuroscience}, year = {2001}, month = {11}, volume = {21}, number = {21}, pages = {8594-8601}, abstract = {A great deal is known about the response properties of single neurons processing sensory information. In contrast, less is understood about the collective characteristics of networks of neurons that may underlie sensory capacities of animals. We used functional magnetic resonance imaging to study the emergent properties of populations of neurons processing motion across different brain areas. Using a visual adaptation paradigm, we localized a distributed network of visual areas that process information about the direction of motion as expected from single-cell recording studies. However, we found an apparent discrepancy between the directional signals in certain visual areas as measured with blood oxygenation level-dependent imaging compared with an estimate based on the spiking of single neurons. We propose a hypothesis that may account for this difference based on the postulate that neuronal selectivity is a function of the state of adaptation. Consequently, neurons classically thought to lack information about certain attributes of the visual scene may nevertheless receive and process this information. We further hypothesize that this adaptation-dependent selectivity may arise from intra- or inter-area cellular connections, such as feedback from higher areas. This network property may be a universal principle the computational goal of which is to enhance the ability of neurons in earlier visual areas to adapt to statistical regularities of the input and therefore increase their sensitivity to detect changes along these stimulus dimensions.}, department = {Department Logothetis}, web_url = {http://www.jneurosci.org/content/21/21/8594.long}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, language = {en}, author = {Tolias, AS and Smirnakis, SM and Augath, MA and Trinath, T and Logothetis, NK} } @Article { 883, title = {Neurophysiological investigation of the basis of the fMRI signal}, journal = {Nature}, year = {2001}, month = {7}, volume = {412}, number = {6843}, pages = {150-157}, abstract = {Functional magnetic resonance imaging (fMRI) is widely used to study the operational organization of the human brain, but the exact relationship between the measured fMRI signal and the underlying neural activity is unclear. Here we present simultaneous intracortical recordings of neural signals and fMRI responses. We compared local field potentials (LFPs), single- and multi-unit spiking activity with highly spatio-temporally resolved blood-oxygen-level-dependent (BOLD) fMRI responses from the visual cortex of monkeys. The largest magnitude changes were observed in LFPs, which at recording sites characterized by transient responses were the only signal that significantly correlated with the haemodynamic response. Linear systems analysis on a trial-by-trial basis showed that the impulse response of the neurovascular system is both animal- and site-specific, and that LFPs yield a better estimate of BOLD responses than the multi-unit responses. These findings suggest that the BOLD contrast mechanism reflects the input and intracortical processing of a given area rather than its spiking output.}, department = {Department Logothetis}, web_url = {http://www.nature.com/nature/journal/v412/n6843/pdf/412150a0.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, DOI = {10.1038/news010712-13}, author = {Logothetis, NK and Pauls, J and Augath, MA and Trinath, T and Oeltermann, A} } @Article { 49, title = {Nonmonotonic noise tuning of BOLD fMRI signal to natural images in the visual cortex of the anesthetized monkey}, journal = {Current Biology}, year = {2001}, month = {6}, volume = {11}, number = {11}, pages = {846-854}, abstract = {Background: The perceptual ability of humans and monkeys to identify objects in the presence of noise varies systematically and monotonically as a function of how much noise is introduced to the visual display. That is, it becomes more and more difficult to identify an object with increasing noise. Here we examine whether the blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) signal in anesthetized monkeys also shows such monotonic tuning. We employed parametric stimulus sets containing natural images and noise patterns matched for spatial frequency and intensity as well as intermediate images generated by interpolation between natural images and noise patterns. Anesthetized monkeys provide us with the unique opportunity to examine visual processing largely in the absence of top-down cognitive modulations and can thus provide an important baseline against which work with awake monkeys and humans can be compared. Results: We measured BOLD activity in occipital visual cortical areas as natural images and noise patterns, as well as intermediate interpolated patterns at three interpolation levels (25\%, 50\%, and 75\%) were presented to anesthetized monkeys in a block paradigm. We observed reliable visual activity in occipital visual areas including V1, V2, V3, V3A, and V4 as well as the fundus and anterior bank of the superior temporal sulcus (STS). Natural images consistently elicited higher BOLD levels than noise patterns. For intermediate images, however, we did not observe monotonic tuning. Instead, we observed a characteristic V-shaped noise-tuning function in primary and extrastriate visual areas. BOLD signals initially decreased as noise was added to the stimulus but then increased again as the pure noise pattern was approached. We present a simple model based on the number of activated neurons and the strength of activation per neuron that can account for these results. Conclusions: We show that, for our parametric stimulus set, BOLD activity varied nonmonotonically as a function of how much noise was added to the visual stimuli, unlike the perceptual ability of humans and monkeys to identify such stimuli. This raises important caveats for interpreting fMRI data and demonstrates the importance of assessing not only which neural populations are activated by contrasting conditions during an fMRI study, but also the strength of this activation. This becomes particularly important when using the BOLD signal to make inferences about the relationship between neural activity and behavior.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science/article/pii/S0960982201002421}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, DOI = {10.1016/S0960-9822(01)00242-1}, author = {Rainer, G and Augath, M and Trinath, T and Logothetis, NK} } @Inproceedings { 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.}, department = {Department Logothetis}, 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}, event_place = {Erice, Italy}, event_name = {9th Workshop of the International School on Magnetic Resonance and Brain Function}, DOI = {10.1016/j.mri.2011.04.005}, author = {Sultan, F and Augath, M and Murayama, Y and Tolias, AS and Logothetis, NK} } @Inproceedings { 3174, title = {Kernel Constrained Covariance for Dependence Measurement}, year = {2005}, month = {1}, pages = {112-119}, abstract = {We discuss reproducing kernel Hilbert space (RKHS)-based measures of statistical dependence, with emphasis on constrained covariance (COCO), a novel criterion to test dependence of random variables. We show that COCO is a test for independence if and only if the associated RKHSs are universal. That said, no independence test exists that can distinguish dependent and independent random variables in all circumstances. Dependent random variables can result in a COCO which is arbitrarily close to zero when the source densities are highly non-smooth. All current kernel-based independence tests share this behaviour. We demonstrate exponential convergence between the population and empirical COCO. Finally, we use COCO as a measure of joint neural activity between voxels in MRI recordings of the macaque monkey, and compare the results to the mutual information and the correlation. We also show the effect of removing breathing artefacts from the MRI recording.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/pdf3174.pdf}, department = {Department Sch{\"o}lkopf}, department2 = {Department Logothetis}, web_url = {http://www.gatsby.ucl.ac.uk/aistats/fullpapers/228.pdf}, editor = {Cowell, R. , Z. Ghahramani}, publisher = {Society for Artificial Intelligence and Statistics}, address = {Fort Lauderdale, FL, USA}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, institution = {MPI for Biological Cybernetics, Spemannstr 38 72076 Tuebingen}, event_place = {Bridgetown, Barbados}, event_name = {Tenth International Workshop on Artificial Intelligence and Statistics (AISTATS 2005)}, language = {en}, ISBN = {0-9727358-1-X}, author = {Gretton, A and Smola, AJ and Bousquet, O and Herbrich, R and Belitski, A and Augath, M and Murayama, Y and Pauls, J and Sch{\"o}lkopf, B and Logothetis, NK} } @Poster { OrtizSALR2012_2, title = {Functional neuroimaging of sound motion in the macaque dorsal stream}, year = {2012}, month = {11}, pages = {43}, abstract = {The macaque ventral intraparietal area (VIP), located in the fundus of the intraparietal sulcus (IPS), is considered a polymodal association area that responds to visual, tactile, vestibular and auditory stimuli. VIP receives projections from multiple visual areas and from auditory regions in the posterior superior temporal (pST) cortex. In humans, several studies have reported activation of the pST and IPS to sound source motion confirming the existence of a dorsal processing stream for spatial aspects of sound in humans. In order to bridge the gap between single-unit recordings in monkeys and neuroimaging studies in humans, we used high-resolution fMRI in monkeys to further investigate these results. First, we created a virtual acoustic space environment using binaural sound recording techniques with miniature microphones inserted into a macaque head cast. We validated the acoustics of the technique and by measuring saccadic eye movements during playback to sound sources we were able to confirm a behavioral response to different locations. We then performed fMRI to identify cortical areas sensitive to sound motion in azimuth of the left and right hemifields. Preliminary results showed that all moving sounds activated areas MT, MST and the IPS. Contrasting left and right sound-motion conditions against center yielded greater activation in contralateral VIP. These results suggest that interaural information induced by lateralized sounds is processed along a dorsal cortical processing stream comprising VIP in the respective contralateral hemisphere.}, department = {Department Logothetis}, web_url = {http://www.danielabalslev.dk/workshop/Abstract_booklet.pdf}, event_place = {T{\"u}bingen, Germany}, event_name = {ERNI-HSF Science Meeting: Orienting of Attention: Neural Implementation, Underlying Mechanisms and Clinical Implications}, author = {Ortiz, M and Steudel, T and Augath, M and Logothetis, NK and Rauschecker, JP} } @Poster { OrtizSALR2012, title = {Functional neuroimaging of sound motion in the macaque dorsal stream}, year = {2012}, month = {9}, day = {1}, volume = {4}, pages = {75}, abstract = {The macaque ventral intraparietal area (VIP), located in the fundus of the intraparietal sulcus (IPS), is considered a polymodal association area that responds to visual, tactile, vestibular and auditory stimuli (Schlack et al., 2005). In particular, VIP neurons are responsive to moving visual and auditory stimuli. VIP receives projections from multiple visual areas (especially from the middle temporal area [MT] and the medial superior temporal complex [MST]) and from auditory regions in the posterior superior temporal (pST) cortex (Lewis \& Van Essen, 2000). Neurons in pST, in particular the caudolateral area (CL), show selective responses to particular sound locations regardless of sound type (Tian et al., 2001; Recanzone, 2001). In humans, several studies have reported activation of the pST and IPS to sound source motion (Warren et al., 2000; Krumbholz et al., 2005), confirming the existence of a dorsal processing stream for spatial aspects of sound in humans. In order to bridge the gap between single-unit recordings in monkeys and neuroimaging studies in humans, we used high-resolution fMRI in monkeys to further investigate these results. First, we created a virtual auditory space environment using binaural sound recording techniques with miniature microphones inserted into a macaque head cast. We validated the technique by measuring saccadic eye movements to sound sources in different locations during playback. We then performed fMRI to identify cortical areas sensitive to sound motion in azimuth of the left and right hemifields. All fMRI data were pre-processed and aligned with the 112RM-SL_T1 rhesus monkey template for identification of cortical fields (McLaren et al., 2009). Preliminary results showed that all moving sounds activated areas MT, MST and the IPS. Contrasting left and right sound-motion conditions against center (i.e. no motion) yielded greater activation in contralateral VIP. These results suggest that interaural information induced by lateralized sounds is processed along a dorsal cortical processing stream comprising VIP in the respective contralateral hemisphere.}, department = {Department Logothetis}, web_url = {http://wp.unil.ch/auditorycortex2012/}, event_place = {Lausanne, Switzerland}, event_name = {4th International Conference on Auditory Cortex}, author = {Ortiz, M and Steudel, T and Augath, M and Logothetis, NK and Rauschecker, JP} } @Poster { ShaoKPFNJALS2012, title = {Population receptive field measurements in the visual cortex of macaque monkeys with and without retinal lesions}, year = {2012}, month = {6}, pages = {82}, 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 formof juvenile macular degeneration (MD). FMRI experiments were performed under light remifentanyl induced anesthesia (Logothetis, et al., Nature Neuroscience, 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 MD monkey, the size and location of the fMRI defined lesion projection zone (LPZ) in early visual areas is consistent with the retinotopic projection of the retinal lesion. No significant activity is found within V1 LPZ of the MD monkey, and the retinotopic organization of the non-deafferented V1 periphery is regular without distortion. Higher level visual areas (V5/MT) of the MD monkey 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 nondeafferented V5/MT of the MD monkey are on average slightly smaller than controls. Further investigation using fMRI and standard electrophysiology methods is in progress.}, department = {Department Logothetis}, web_url = {http://areadne.org/2012/home.html}, event_place = {Santorini, Greece}, event_name = {AREADNE 2012: Research in Encoding and Decoding of Neural Ensembles}, author = {Shao, Y and Keliris, GA and Papanikolaou, A and Fischer, DM and Nagy, D and Jaegle, H and Augath, M and Logothetis, NK and Smirnakis, SM} } @Poster { AzadbakhtPHALdDP2012, title = {Validation of tractography against in vivo tracing in the macaque visual system: effect of distance correction}, year = {2012}, month = {5}, day = {9}, volume = {20}, pages = {1104}, abstract = {Validation of diffusion imaging has proved difficult due to the lack of an adequate gold-standard. In this work, the macaque visual system is used as a model, in which due to an extensive literature of in-vivo and post-mortem tracer studies, “true” connections are well-established. We performed probabilistic tractography on diffusion imaging data from two in-vitro macaque brains, and comparisons were made between identified connections at different thresholds of connection strength, and connections identified in the visual system wiring map of Felleman \& van Essen. The effects of streamline-length based correction of the distance bias of probabilistic tractography were also explored.}, department = {Department Logothetis}, web_url = {http://www.ismrm.org/12/tp_12.htm}, event_place = {Melbourne, Australia}, event_name = {20th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2012)}, author = {Azadbakht, H and Parkes, LM and Haroon, HA and Augath, M and Logothetis, NK and de Crespigny, A and D’Arceuil, HE and Parker, GJM} } @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.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/am2011/}, event_place = {Washington, DC, USA}, event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)}, author = {Shao, Y and Keliris, GA and Papanikolaou, A and Augath, M and Logothetis, NK and Smirnakis, SM} } @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}, 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).}, department = {Department Logothetis}, web_url = {http://www.frontiersin.org/10.3389/conf.fnhum.2011.207.00181/event_abstract}, event_place = {Palma, Mallorca, Spain}, event_name = {XI International Conference on Cognitive Neuroscience (ICON XI)}, DOI = {10.3389/conf.fnhum.2011.207.00181}, author = {P{\'e}rez, A and Iturria-Medina, Y and Morris, D and Canales-Rodr{\'i}guez, E and Haroon, H and Garc{\'i}a, l and Augath, M and Logothetis, NK and Melie-Garcia, L and Parker, G} } @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 \verb=~= 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.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/am2010/index.aspx?pagename=abstracts_main}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {San Diego, CA, USA}, event_name = {40th Annual Meeting of the Society for Neuroscience (Neuroscience 2010)}, language = {en}, author = {Shao, Y and Keliris, GA and Papanikolaou, A and Fischer, DM and Nagy, D and J{\"a}gle, H and Seeliger, MW and Augath, M and Logothetis, NK and Smirnakis, SM} } @Poster { KirschASSS2010, title = {In vivo chlorine-35, sodium-23 and proton magnetic resonance imaging of the rat brain}, year = {2010}, month = {5}, day = {4}, 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.}, url = {http://www.kyb.tuebingen.mpg.defileadmin/user_upload/files/publications/ISMRM-2010-981.PDF}, department = {Department Logothetis}, talk_type = {Abstract Talk}, web_url = {http://www.ismrm.org/10/}, event_place = {Stockholm, Sweden}, event_name = {ISMRM-ESMRMB Joint Annual Meeting 2010}, author = {Kirsch, S and Augath, M and Seiffge, D and Schilling, R and Schad, LR} } @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\(^{\circ}\)C to a target temperature of 15\(^{\circ}\)C (0.5\(^{\circ}\)C/sec) followed by a re-warming to baseline (0.5\(^{\circ}\)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.}, department = {Department Logothetis}, web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=900967bd-51c4-4851-bf1c-9ac4ab8672ed\&cKey=50872dae-3636-42e4-a7d3-d49edcf1e79e}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Chicago, IL, USA}, event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)}, language = {en}, author = {Evrard, HC and Augath, M and Baumg{\"a}rtner, U and Craig, AD and Treede, RD and Logothetis, NK} } @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.}, department = {Department Logothetis}, web_url = {http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=aa77b529-16c6-4a04-9bcb-f2d0780872b0\&cKey=21bfa24c-ac10-43f7-9822-9a476aaa6d19}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Chicago, IL, USA}, event_name = {39th Annual Meeting of the Society for Neuroscience (Neuroscience 2009)}, language = {en}, author = {Sultan, FR and Augath, M and Hamodeh, S and Murayama, Y and Thier, P and Logothetis, NK} } @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}, day = {20}, 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.}, url = {http://www.kyb.tuebingen.mpg.defileadmin/user_upload/files/publications/ISMRM-2009-02471.pdf}, department = {Department Logothetis}, web_url = {http://www.ismrm.org/09/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Honolulu, HI, USA}, event_name = {17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009)}, language = {en}, author = {Augath, M and Heiler, P and Kirsch, S and Schad, LR} } @Poster { SultanAMHTL2009, title = {Revealing Excitable Subcortical Networks by Microstimulationf-MRI of the Deep Cerebellar Nuclei}, year = {2009}, month = {3}, pages = {1067}, abstract = {Electrical stimulation, combined with functional magnetic resonance imaging (es-fMRI), is proving to be an important tool to study the functional properties of spatially distributed neuronal networks of the brain. Here, we want to understand how information is propagated between the two major cortices of the primate brain, the neocortex and the cerebellar cortex. We therefore electrically stimulated the deep cerebellar nuclei of rhesus monkeys. So far we have electrically stimulated 19 different sites in different parts of the deep cerebellar nuclei. Electrical stimulation of the DCN leads to reliable transsynaptic responses in the neocortex. Surprisingly, the BOLD responses can be observed in multiple neocortical sites extending beyond classical cerebellar targets (such as primary motor cortex) and also extending to the hemisphere ipsilateral to the stimulation site. An analysis of the BOLD amplitude in cortical and subcortical structures indicated that the bilateral spread of activity is already present at subcortical levels, i.e. the thalamus. Currently we cannot exclude the possibility that we stimulated fibres of passage that then activated the contralateral DCN and hence contributed to the bilateral neocortical activation patterns. However, the observation of wide-spread BOLD responses in thalamic regions outside the known thalamic termination sites of the DCN indicates that the DCN are able to drive brainstem circuits effectively that then reach neocortex through several thalamic nuclei. These results indicate that, apart from the direct DCN -thalamic projection, indirect routes exist by which the cerebellum can mediate information to the neocortex that may be equally important and effective despite requiring the additional passage through synapses in met- and mesencephalic structures.}, department = {Department Logothetis}, web_url = {http://www.nwg-goettingen.de/2009/}, event_place = {G{\"o}ttingen, Germany}, event_name = {8th G{\"o}ttingen Meeting of the German Neuroscience Society, 32nd G{\"o}ttingen Neurobiology Conference}, author = {Sultan, F and Augath, M and Murayama, Y and Hamodeh, S and Thier, P and Logothetis, NK} } @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 {\`i}voice{\^A}” 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.}, department = {Department Logothetis}, web_url = {http://www.aro.org/archives/2009/2009_1111_e15f0394.html}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Baltimore, MD, USA}, event_name = {32nd Annual Midwinter Meeting of the Association for Research in Otolaryngology (ARO 2009)}, language = {en}, author = {Petkov, CI and Kikuchi, Y and Augath, M and Mishkin, M and Rauschecker, J and Logothetis, NK} } @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 \(\mu\)A pulses of 200 \(\mu\)s 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.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/annual-meeting/past-and-future-annual-meetings}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Washington, DC, USA}, event_name = {38th Annual Meeting of the Society for Neuroscience (Neuroscience 2008)}, language = {en}, author = {Kikuchi, Y and Rauschecker, JP and Mishkin, M and Augath, M and Logothetis, NK and Petkov, CI} } @Poster { HaroonMKALP2008, title = {Comparing Corticocortical Interconnection Information from Tracer Studies and Probabilistic Tractography in the Postmortem Macaque Brain}, year = {2008}, month = {5}, day = {8}, volume = {16}, 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.}, url = {http://www.kyb.tuebingen.mpg.defileadmin/user_upload/files/publications/ISMRM-2008-03369.pdf}, department = {Department Logothetis}, web_url = {http://www.ismrm.org/08/}, event_place = {Toronto, Canada}, event_name = {16th Scientific Meeting and Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM 2008)}, author = {Haroon, HA and Morris, DM and Kaiser, A and Augath, M and Logothetis, NK and Parker, GJM} } @Poster { 5001, title = {Multisensory interactions in auditory cortex}, year = {2007}, month = {11}, volume = {37}, number = {620.15}, abstract = {An increasing body of literature provides compelling evidence that sensory convergence not only occurs in higher association areas, but also in lower sensory regions and even in primary sensory cortices. To scrutinize these early cross-modal interactions, we use the macaque auditory cortex as model and employ combinations of high-resolution functional imaging (fMRI) and electrophysiological recordings. Using function imaging in alert and anaesthetized animals, we reported that (only) caudal auditory fields are susceptible to cross-modal modulation: The fMRI-BOLD response in these regions was enhanced when auditory stimuli were complemented by simultaneous visual or touch stimulation [see Kayser et al. Neuron 48, 2005 and J. Neurosci. 27(8), 2007]. To investigate the neuronal basis of this cross-modal enhancement, we recorded the activity of local field potentials and single units in alert animals watching complex audio-visual scenes. Our results show the following: Visual stimuli by themselves, on average, do not drive auditory neurons, but cause responses in low frequency LFPs. Combining visual and auditory stimuli leads to enhanced responses in the low frequency LFP, but to a reduction of firing rates. This audio-visual interaction was significant at the population level, and for about 10\% of the neurons when tested individually. The interaction occurs only for well-timed visual stimuli, is strongest when the visual stimulus leads the auditory stimulus by 20-80msec, but is independent of the image structure in the visual stimulus. Smilar visual modulation was found in the auditory core and belt. Our findings point to a very basic, stimulus unspecific visual input to auditory cortex and clearly support the notion that early sensory cortices are susceptible to cross-modal interactions. Especially, the finding that visual stimuli modulate the firing rates of individual neurons in auditory cortex suggests that the messages transmitted from these regions to higher processing stages do not only reflect acoustical stimuli but are also dependent on their visual context.}, department = {Department Logothetis}, department2 = {Research Group Kayser}, web_url = {http://www.sfn.org/am2007/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {San Diego, CA, USA}, event_name = {37th Annual Meeting of the Society for Neuroscience (Neuroscience 2007)}, language = {en}, author = {Kayser, C and Petkov, CI and Augath, M and Logothetis, NK} } @Poster { 4586, title = {A voice-area in the primate brain: Enhanced representation of the ''voice'' of conspecifics}, year = {2007}, month = {9}, abstract = {The human voice not only transmits spoken language, but itself carries considerable meaning. Reflecting this importance, imaging studies have identified a region in the auditory cortex of the human brain that is sensitive to the human voice. For animals that cannot expand their vocal repertoire linguistically, the correct interpretation of the vocalizations of their conspecifics is of even greater importance for survival and social interactions. However, it is uncertain whether other primates share homologous voice regions or whether the human voice area is tightly linked to human language and thus unique. Here, we used high-resolution functional imaging (fMRI) of macaque monkeys to compare the strength of the activity response to conspecific vocalizations with that elicited by other sound categories, including the vocalizations of heterospecifics. We found several brain regions demonstrating a strong preference for conspecific vocalizations and identified a candidate ‘voice’ area located in the higher proc essing stages of auditory cortex, in the anterior portions of the superior-temporal plane (STP). In contrast, the corresponding well-known human voice area resides below the STP, highlighting the possibility of an evolutionary expansion and differentiation of the human auditory cortex away from the STP. The presence of a voice region in nonhuman primates supports the notion that such specialized areas do not depend on linguistic capabilities. In all cases, our findings suggest that the auditory cortex of other vocal animals possess regions that are specialized for processing the ‘voice‘ of conspecifics.}, department = {Department Logothetis}, web_url = {http://www.dzg-ev.de/de/veranstaltungen/externe/eec2007.php}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Hannover, Germany}, event_name = {International Symposium on Evolution of Emotional Communication (EEC 2007)}, language = {en}, author = {Petkov, CI and Kayser, C and Whittingstall, K and Steudel, T and Augath, M and Logothetis, NK} } @Poster { 4125, title = {Functional imaging of organization and specialization in the monkey auditory cortex}, journal = {Hearing Research}, year = {2007}, month = {7}, volume = {229}, number = {1-2}, pages = {239-240}, abstract = {We localized many fields in the auditory cortex of the macaque monkey and studied which auditory regions are specialized for processing the communication sounds of the species. First, we used high resolution fMRI at 4.7 and 7 T to functionally map the auditory cortex of behaving and of anesthetized monkeys. The identified fields included regions already well described by anatomical and neurophysiological techniques as well as those whose anatomical parcellation remained without functional support. To localize fields, we varied the frequencies of tonal or bandpassed-noise sounds, and obtained spatially specific activity patterns throughout much of auditory cortex. We then statistically tested the frequency-selective gradients within these regions of auditory cortex and the results suggest that 11 fields contain neurons tuned for the frequency of sounds. The obtained maps provide functional support for a model according to which three fields in primary auditory cortex (the auditory ‘core’) are surrounded by eight neighboring ‘belt’ fields in non-primary auditory cortex. Following this non-invasive mapping, we examined which of the localized fields, if any, were specialized for processing the communication sounds of these species in relation to other sounds. Natural sounds were presented as stimulation, including the vocalizations of conspecifics, of other animals, and other natural sounds. Control stimuli were also used. The vocalizations of conspecifics generally elicited greater responses throughout auditory cortex than did the other sounds. The strongest specificity for these vocalizations seemed to be in the anterior fields of auditory cortex, but also extended anteriorly outside of the auditory core and belt fields that were localized with tone and noise stimuli. The data suggest a specialization for the processing of species-specific vocalizations in the anterior portions of auditory cortex, including the poorly understood fields of the auditory parabelt. These fMRI data reflect ethological influences on brain organization and can help us to delineate neural networks in the nonhuman primate that are expected to have an evolutionary relationship to speech processing areas in the human brain.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science/article/pii/S0378595506003108}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Grantham, UK}, event_name = {2nd International Conference on Auditory Cortex 2006: The Listening Brain}, DOI = {10.1016/j.heares.2006.11.003}, author = {Petkov, CI and Kayser, C and Augath, M and Steudel, T and Logothetis, NK} } @Poster { ShmuelAOL2007, title = {Spontaneous fluctuations in functional MRI signal reflect fluctuations in the underlying local neuronal activity}, journal = {NeuroImage}, year = {2007}, month = {6}, volume = {36}, number = {Supplement 1}, pages = {S58}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science/article/pii/S1053811907002789}, event_place = {Chicago, IL, USA}, event_name = {13th Annual Meeting of the Organization for Human Brain Mapping (HBM 2007)}, DOI = {10.1016/j.neuroimage.2007.03.045}, author = {Shmuel, A and Augath, M and Oeltermann, A and Logothetis, NK} } @Poster { KayserPAL2007, title = {Cross-modal integration of sensory information in auditory cortex}, journal = {Neuroforum}, year = {2007}, month = {4}, volume = {13}, number = {Supplement}, pages = {835}, abstract = {Traditionally it is assumed that information from different sensory systems merges in higher association cortices. Contrasting this belief, we demonstrate cross-modal integration in primary and secondary auditory cortex. Using a combination of high-resolution functional magnetic resonance imaging (fMRI) and electrophysiological recordings in macaque monkeys, we quantify the integration of visual and tactile stimulation with auditory processing. Integration manifests as enhancement of activity that exceeds a simple linear superposition of responses, i.e. auditory activity is enhanced by the simultaneous presentation of non-auditory stimuli. Audio-somatosensory integration is reliably found at the caudal end and along the lateral side of the secondary auditory cortex. Regions with significant integration respond to auditory but only few to somatosensory stimulation. Yet, combining both stimuli significantly enhances responses. This enhancement obeys the classical rules for cross-modal integration: it occurs only for temporally coincident stimuli and follows the principle of inverse effectiveness; integration is stronger for less effective stimuli. Audio-visual integration is similarly found along the caudal end of the temporal plane in secondary auditory cortex, but also extends into primary auditory fields. Complementing these results from functional imaging, enhancement of neuronal activity is found in electrophysiological recordings of single neuron and population responses. Hence, we conclude that cross-modal integration can occur very early in the processing hierarchy - at the earliest stage of auditory processing in the cortex. Further, this multisensory integration occurs pre-attentive, as demonstrated in anaesthetized animals. Such early integration might be necessary for quick and consistent interpretation of our world and might explain multisensory illusions where a stimulus perceived by one modality is altered by a stimulus in another modality.}, department = {Research Group Kayser}, department2 = {Department Logothetis}, web_url = {http://nwg.glia.mdc-berlin.de/media/pdf/conference/Proceedings-Goettingen2007.pdf}, event_place = {G{\"o}ttingen, Germany}, event_name = {7th Meeting of the German Neuroscience Society, 31st G{\"o}ttingen Neurobiology Conference}, author = {Kayser, C and Petkov, C and Augath, M and Logothetis, NK} } @Poster { SchmidALS2007, title = {Retinotopic activation of macaque area V2 without input from primary visual cortex}, journal = {Neuroforum}, year = {2007}, month = {4}, volume = {13}, number = {Supplement}, pages = {737}, abstract = {The presence of focal lesions in primary visual cortex (V1) provides the opportunity to study the role of extra-geniculo-striate pathways for activating extra-striate visual cortex. Previous studies in the macaque have shown that cells in area V2 stop firing after reversibly cooling V1 (Girard and Bullier, 1989; Schiller et al., 1974). However no studies on long term recovery after V1 lesions have been reported in the macaque. Here we use fMRI of the macaque monkey brain to study the organization of V2 from baseline levels up to 16 months post-lesioning. We find that BOLD responses in the lesion projection zone (LPZ) of area V2 are reduced by 80 \% compared to pre-lesion levels. Surprisingly the retinotopic organization inside the area V2 LPZ is similar before and after inducing the V1 lesion, suggesting that V2 activation is not the result of input arising from nearby non-lesioned V1 cortex. Monitoring of the activity over time after the lesion did not reveal systematic changes in signal amplitude near the LPZ border. We conclude that visually driven activation of extra-striate area V2 as revealed by the BOLD signal is 1) significantly reduced, but still present after depriving it of V1 input, 2) the area V2 LPZ largely retains its original retinotopic organization, and 3) the strength of visual modulation inside the LPZ does not seem to increase significantly up to 16 months post-lesioning. We discuss our findings in the context of parallel pathways in the brain which can activate V2 in the absence of V1 input and may contribute to the behavioral phenomenon of blindsight.}, department = {Department Logothetis}, web_url = {http://nwg.glia.mdc-berlin.de/media/pdf/conference/Proceedings-Goettingen2007.pdf}, event_place = {G{\"o}ttingen, Germany}, event_name = {7th Meeting of the German Neuroscience Society, 31st G{\"o}ttingen Neurobiology Conference}, author = {Schmid, M and Augath, M and Logothetis, NK and Smirnakis, S} } @Poster { 5285, title = {Mapping responses to natural stimuli in the primate brain: visual flow, retinotopy and tonotopy}, year = {2007}, month = {3}, department = {Department Logothetis}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Erice, Italy}, event_name = {V. Workshop of the International School on Magnetic Resonance and Brain Function (ISMRBF 2007)}, author = {Bartels, A and Moutoussis, K and Maugath and Zeki, S and Logothetis, N} } @Poster { 4126, title = {Organization and specialization of the monkey auditory cortex revealed with MR imaging}, year = {2006}, month = {10}, day = {13}, department = {Department Logothetis}, web_url = {http://www.apan.jhu.edu/Program_APANIV.htm}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Atlanta, GA, USA}, event_name = {Tucker-Davis Symposium on Advances and Perspectives in Auditory Neurophysiology (APAN IV)}, author = {Petkov, C and Kayser, C and Augath, M and Steudel, T and Logothetis, N} } @Poster { 4123, title = {Functional imaging of organization and specialization in the monkey auditory cortex}, year = {2006}, month = {10}, volume = {36}, number = {344.9}, abstract = {We localized numerous fields in the auditory cortex of the macaque monkey and studied which regions are specialized for processing the communication sounds of the species. First, we used high resolution fMRI at 4.7 and 7 Tesla to functionally map the auditory cortex of behaving and of anesthetized monkeys. The identified fields included regions already well described by anatomical and neurophysiological techniques as well as those whose anatomical parcellation remained without functional support. To localize fields, we varied the frequency content of tonal or band-passed-noise sounds, and obtained spatially specific activity patterns throughout much of auditory cortex. We then statistically tested the frequency-selective gradients within these regions of auditory cortex and the results suggest that 11 fields contain neurons tuned for the frequency of sounds. The obtained maps provide functional support for a model according to which three fields in primary auditory cortex (the auditory ‘core’) are surrounded by eight neighboring ‘belt’ fields in non-primary auditory cortex. Following this non-invasive mapping, we examined which of the localized fields, if any, were specialized for processing the communication sounds of these species in relation to other sounds. Natural sounds were presented as stimulation, including the vocalizations of conspecifics, of other animals, and other natural sounds. Control stimuli were also used. The vocalizations of conspecifics generally elicited greater responses throughout auditory cortex than did the other sounds. The strongest specificity for these vocalizations seemed to be in the anterior fields of auditory cortex, but also extended anteriorly outside of the auditory core and belt fields that were localized with tone and noise stimuli. The data suggest a specialization for the processing of species-specific vocalizations in the anterior portions of auditory cortex, including the poorly understood fields of the auditory parabelt. These fMRI data reflect ethological influences on brain organization and can help us to delineate neural networks in the nonhuman primate that are expected to have an evolutionary relationship to speech processing areas in the human brain.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/Petkov_et_al_SFN\%20Abstract\%2006_final_4123[0].pdf}, department = {Department Logothetis}, web_url = {http://www.sfn.org/index.aspx?pagename=abstracts_ampublications}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Atlanta, GA, USA}, event_name = {36th Annual Meeting of the Society for Neuroscience (Neuroscience 2006)}, author = {Petkov, C and Kayser, C and Augath, M and Steudel, T and Logothetis, NK} } @Poster { 3940, title = {Decoupling of BOLD and neuronal activity in the gamma range during recovery from lidocaine inactivation}, year = {2006}, month = {7}, volume = {5}, number = {A179.20}, pages = {143}, abstract = {The underlying neurophysiological source of the BOLD signal is still not fully understood. The spike rate of single neurons is only poorly correlated with the time course of the BOLD signal. The BOLD signal seems rather to reflect the activity of the presynaptic network the neurons are embedded in. We therefore blocked the neuronal activity in a defined area with lidocaine, a reversible sodium channel blocker. In this way we could investigate, how the BOLD signal is coupled to the neuronal activity. The effects were assessed by simultaneous intracortical recordings and fMRI. We examined BOLD responses in regions of interest defined by independent localizer scans, and assessed the spatial effect of the blocker at varying distances from the injection site. Neuroimaging was performed in a 4.7 Tesla Scanner. We recorded multiunit activity (MUA) and local field potentials (LFPs). V1 was stimulated by rotating polar checkerboard stimulus. At a distance of 400 microns to the recording electrode we injected Lidocaine (2-6\%). Applied quantities (5-25 microl) and flow rates (0.8-4 microl /min) were monitored by a flow meter. Lidocaine injections were associated with reliable decreases in neuronal activity and local decreases in BOLD activity. Both neuronal and BOLD signals recovered at a timescale of several minutes. However, early in the recovery phase there was a clear transient increase in the gamma band LFP, while the MUA activity was still blocked. The BOLD signal showed a stimulus-modulated increase due to recovery, which however paralled neither the transient increase in LFP nor the still unmodulating MUA signal. The early period in the recovery from lidocaine inactivation thus represents a cortical state in which BOLD signal levels are largely decoupled from the neuronal ones. Our findings suggest that even general blockers (lidocaine) can generate interesting states of neurovascular decoupling that can be used for a better understanding of the BOLD signal.}, department = {Department Logothetis}, web_url = {http://fens2006.neurosciences.asso.fr/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Wien, Austria}, event_name = {5th Forum of European Neuroscience (FENS 2006)}, author = {Rauch, A and Augath, M and Oeltermann, A and Rainer, G and Logothetis, NK} } @Poster { 5284, title = {Natural movie stimuli allow mapping of retinotopy and tonotopy in anesthetized monkey cortex}, year = {2006}, month = {6}, pages = {37}, abstract = {In traditional functional magnetic resonance imaging (fMRI) carefully controlled stimuli are used to reveal cortical regions that are differentially responsive to distinct stimuli. In human fMRI studies we have shown that the varying intensity of features, such as faces or color, seen in a movie, can be used to map feature selective regions, such as the human V4 complex for color or superior temporal regions (STS) and lateral fusiform cortex (FFA) for faces (Bartels \& Zeki, 2004). Here we applied the same paradigm in the anesthetized monkey to identify regions involved in processing various low- and highlevel features. The advantage of this approach is that effects of attention or eye-movements can be excluded. In early visual cortex (V1-V3) we found that the BOLD signal was predicted by both, changes in frame-by-frame pixel intensities (luminance changes) as well as by image contrast. These two measures were not correlated with each other in our movie stimulus. Early visual cortex thus seems to code for two independent stimulus dimensions. Responses to each were so specific that we were able to obtain retinotopic maps by correlating voxel-time series with time series of either of these stimulus dimensions as a function of their spatial location in the movie display. In contrast, color and face variations correlated most with BOLD signal changes in V4 and in the STS. In auditory cortex, we were able to obtain tonotopic maps based on the movie soundtrack, by correlating sound intensities at different frequencies with BOLD signal of every voxel. Our results illustrate that, in monkey as in man, movies - even though uncontrolled - allow surprisingly specific mapping of high- as well as low-level features, down to retinotopy and tonotopy.}, department = {Department Logothetis}, web_url = {http://www.areadne.org/2006/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Santorini, Greece}, event_name = {AREADNE 2006: Research in Encoding and Decoding of Neural Ensembles}, language = {en}, author = {Bartels, A and Maugath and Moutoussis, K and Zeki, S and Logothetis, N} } @Poster { 3539, title = {fMRI of Macaque Auditory Cortex in Awake and in Anesthetized Animals}, year = {2005}, month = {11}, volume = {35}, number = {851.5}, abstract = {Functional magnetic resonance imaging (fMRI) with non-human primates is invaluable because localized patterns of activity can guide subsequent neurophysiological recordings. However, it is unknown whether fMRI of the macaque monkey can reveal reliable auditory activations consistent with known properties of primate auditory cortical fields (ACFs). We used high-field (4.7- and 7-Tesla) fMRI to image the blood-oxygen level dependent response (BOLD) of auditory cortex in awake and in anesthetized macaques. For awake-animal imaging we trained a macaque to complete long duration trials of visual fixation in combination with minimal body movement. Scanning this animal at 7T during sound presentation revealed robust activity over auditory cortex in the superior temporal plane. A paradigm where stimulation alternated with image acquisition revealed greater auditory activity than continuous imaging where sound stimulation must compete with the scanner noise. Imaging data with more extensive sound stimulation was obtained from anesthetized animals since these experiments allow for quicker data acquisition. Here, we used sounds varying in center frequency and bandwidth as have neurophysiological experiments mapping the basic organizational properties of macaque ACFs. In the antero-posterior direction, regions within the lateral sulcus were selective for sounds with low and high center frequencies, revealing expected frequency selective gradients (tonotopy) with multiple mirror reversals of these gradients. In comparison to tonal stimulation, sounds with greater spectral bandwidth activated more lateral and medial portions of the superior temporal plane, consistent with this activity occurring over non-primary ACFs. In summary, high-field fMRI reveals the global organization of macaque auditory cortex and will be important for helping us to understand how the primate auditory cortex is functionally organized.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Washington, DC, USA}, event_name = {35th Annual Meeting of the Society for Neuroscience (Neuroscience 2005)}, language = {en}, author = {Petkov, CI and Kayser, C and Augath, M and Steudel, T and Logothetis, NK} } @Poster { 3549, title = {Integration of touch and sound in auditory cortex}, year = {2005}, month = {11}, volume = {35}, number = {388.6}, abstract = {Our different senses provide complementary views of the environment, and integrating information across senses is necessary for disambiguating sensory objects and for reliable interaction with these. Supposedly, multisensory information is integrated only by higher cortical association areas. Contrasting this belief, we demonstrate multisensory integration in areas proximal to primary sensory areas - in the so called auditory belt. Using functional magnetic resonance imaging (fMRI) of macaque monkeys, we quantified the integration of simultaneous audio-visual and audio-tactile stimulation in anaesthetized animals at 4.7Tesla. Technically, integration was assumed if the response to the combined stimulus was stronger than the sum of the responses to individual stimuli. Integration of auditory broad-band noise with tactile stimulation of hands and foot was found at the posterior end and along the lateral side of the auditory belt in six animals. This integration occurred only for temporally coincident stimuli and obeyed the principle of inverse effectiveness: integration was stronger for less effective stimuli. Voxels with significant integration responded to auditory alone stimulation but only few to tactile alone. Combining visual and auditory stimulation in different paradigms we could not find robust multisensory integration in auditory cortex. Further, audio-tactile integration was mostly limited to auditory cortex and much weaker in nearby ‘multimodal’ areas such as the claustrum. Our findings demonstrate that multisensory integration can occur early in the processing hierarchy - one processing stage above primary auditory cortex. Further, this multisensory integration occurred pre-attentive - as demonstrated in anaesthetized animals. Such early integration might be necessary for quick and consistent interpretation of our world and might explain multisensory ‘illusions’ where a stimulus perceived by one modality is altered by a stimulus in another modality.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Washington, DC, USA}, event_name = {35th Annual Meeting of the Society for Neuroscience (Neuroscience 2005)}, language = {en}, author = {Kayser, C and Petkov, C and Augath, M and Logothetis, NK} } @Poster { 4505, title = {Macaque visual cortex organization probed by fMRI after area V1 lesions}, year = {2005}, month = {11}, volume = {35}, number = {979.10}, abstract = {Under certain conditions, lesions of the adult central nervous system can induce reorganization of cortical sensory representations in the brain. This capacity of cortical circuitry for reorganization can potentially contribute in accelerating recovery after nervous system injury, such as stroke. In the visual system, extrastriate cortex has been shown to reorganize in an adult human subject with an extensive lesion of the primary visual cortex (Baseler et al., J Neurosci 1999). However, the extent and time course of the process of reorganization after focal area V1 lesions remains incompletely characterized. Here we use functional magnetic resonance imaging (fMRI) to characterize how the topography of early macaque visual areas changes following V1 lesions. After creating a \verb=~=1.2 cm x 1.2 cm lesion in area V1 by aspiration, we used 4.7 T fMRI in the anesthetised macaque preparation (Logothetis et al. Nat Neurosci 1999) to monitor changes in the topographic maps of early visual areas (V2, V3) as a function of time. The stimuli we used to map the topography of visual areas were a standard ring/wedge retinotopic stimulation paradigm (Brewer et al. J Neurosci, 2002) as well as a \verb=~=20 degree x 27 degree rotating checkerboard stimulus alternating with uniform background illumination. Both stimuli have been previously shown to activate reliably early visual areas (Smirnakis et al., Nature, 2005). Preliminary results revealed a localized cortical region within area V2/V3 whose visual modulation was strongly diminished following the V1 lesion. By monitoring how the strength of the visual modulation inside this region evolves in time we will quantify the degree of reorganization seen in area V2/V3.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Washington, DC, USA}, event_name = {35th Annual Meeting of the Society for Neuroscience (Neuroscience 2005)}, language = {en}, author = {Smirnakis, SM and Schmid, MC and Tolias, AS and Augath, M and Logothetis, NK} } @Poster { 3831, title = {Movie presentation allows mapping of retinotopy, color, and face-related activity in the anesthetized monkey brain}, year = {2005}, month = {11}, volume = {35}, number = {46.11}, abstract = {In traditional functional magnetic resonance imaging (fMRI) carefully controlled stimuli are used to reveal cortical regions that are differentially responsive to distinct stimuli. In human fMRI studies we have shown that the varying intensity of features, such as faces or color, seen in a movie, can be used to map feature selective regions, such as the human V4 complex for color or superior temporal regions (STS) and lateral fusiform cortex (FFA) for faces (Bartels \&amp; Zeki, 2004). Here we applied the same paradigm in the anesthetized monkey to identify regions involved in processing various low- and high-level features. The advantage of this approach is that effects of attention or eye-movements can be excluded. We found that the BOLD signal in V1 was best predicted by changes in frame-by-frame pixel intensities (contrast changes) compared to measures of contrast, luminance or spatial frequency. BOLD signal in response to contrast changes were specific enough to reveal the retinotop y of V1 and V2 as a function of their spatial location throughout the movie. Color variations correlated most with BOLD signal in V4 and weakly along the STS. Face specific responses extended along the STS, and overlapped partly with the regions also responsive to color. We conclude that, in monkey as in man, movies - even though uncontrolled - allow surprisingly specific mapping of high- as well as low-level features, down to retinotopy. In addition, regions identified this way may reflect more realistically processing in natural, more complex and dynamic environments.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Washington, DC, USA}, event_name = {35th Annual Meeting of the Society for Neuroscience (Neuroscience 2005)}, language = {en}, author = {Bartels, A and Augath, M and Moutoussis, K and Zeki, S and Logothetis, NK} } @Poster { 3941, title = {The effect of lidocaine on neural activity and BOLD activity in monkey primary visual cortex}, year = {2005}, month = {11}, volume = {35}, number = {742.15}, abstract = {The neurophysiological basis of BOLD contrast mechanism in fMRI is not fully understood. Therefore we started to investigate the role of different neuromodulators and channel blockers on the neural and hemodynamic responses. We first report the effects of local injection of Lidocaine, a reversible sodium channel blocker, in primary visual cortex (V1) of anesthetized monkeys. The effects were assessed by simultaneous intracortical recordings and fMRI. We examined BOLD responses in regions of interest defined by independent localizer scans, and assessed the spatial effect of the blocker at varying distances from the injection site. 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 \(\mu\)m to the recording electrode we injected Lidocaine (2\% solution) with a precision pump (M6 VICI, USA). Applied quantities (8-25 \(\mu\)l) and flow rates (0.8-4 \(\mu\)l /min) were monitored by a precision flow meter (Sensirion, Switzerland). Consistent with previous reports, Lidocaine induced reliable decreases in neuronal activity at the injection site. In addition, we observed clear decreases in BOLD activity. The largest effect on both signals was observed closest to the injection site and decreased with increasing distance. The effect was reversible for both signals with a recovery time of 20-30 minutes. Injection of saline (0.9\%), to rule out nonspecific effects, showed no change in neuronal or BOLD signals. The findings suggest a close coupling between stimulus-evoked neuronal activity and the BOLD signal. This allows for a better quantification of the primarily interesting part of the BOLD signal involved in neuronal processing as we now can distinguish between the BOLD signal needed for information processing and the portion used for homeostasis of neurons and their embedding glial cells.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Washington, DC, USA}, event_name = {35th Annual Meeting of the Society for Neuroscience (Neuroscience 2005)}, language = {en}, author = {Rauch, A and Augath, M and Oeltermann, A and Rainer, G and Logothetis, NK} } @Poster { KourtziALMK2004, title = {Development of global form and motion perception in monkeys studied with fMRI}, year = {2004}, month = {10}, volume = {34}, number = {66.14}, abstract = {Perceptual integration is critical for perception and interpretation of the visual world. Psychophysical studies suggest that these integrative processes for global form and motion develop slowly: when spatial resolution and contrast sensitivity approach adult levels (6-9 months in monkeys), global form and motion perception are still immature. The goal of this study was to investigate the neural development of perceptual integration by using fMRI on anesthetized macaques at different developmental stages. We examined the functional development of higher extrastriate visual areas whose delayed development might be responsible for the late maturation of coherent form and motion perception. We used Glass patterns, random dot patterns in which global structure is defined by the spatial or spatio-temporal orientation of correlated dot pairs to form contour and motion stimuli with identical local statistics but different global forms (e.g. radial, concentric). To compare form and motion processing directly, we used static and dynamic (patterns with both spatial and temporal offset between dots) Glass patterns to activate the ventral and dorsal pathways, respectively. We compared fMRI responses for static and dynamic Glass patterns to those for static and dynamic random noise patterns. Experiments in adult macaques showed stronger activations for static Glass than random patterns in ventral extrastriate visual areas, whereas stronger activations for dynamic Glass than random patterns were observed in dorsal motion areas. Longitudinal study of two infant monkeys from the age of 8 months showed some differential activation for dynamic than random patterns but not for static Glass patterns. These results are consistent with previous perceptual and neurobiological evidence that the dorsal extrastriate pathway develops more quickly than the ventral pathway.}, department = {Department B{\"u}lthoff}, department2 = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, event_place = {San Diego, CA, USA}, event_name = {34th Annual Meeting of the Society for Neuroscience (Neuroscience 2004)}, author = {Kourtzi, Z and Augath, M and Logothetis, NK and Movshon, JA and Kiorpes, L} } @Poster { 4504, title = {Spatial specificty of BOLD versus MION in a macaque fMRI preparation at 47T}, year = {2004}, month = {10}, volume = {34}, number = {646.10}, abstract = {Most macaque functional magnetic resonance imaging (fMRI) studies are based on monitoring the intrinsic blood oxygen level dependent signal (BOLD) or, alternatively, on measuring changes in cerebral blood volume (CBV) after injection of the intravascular contrast agent MION (monocrystalline iron oxide nanoparticles). In comparison to BOLD, imaging using MION results in higher contrast to noise ratios (CNR) (Leite et al., 2002; Vanduffel et al., 2001). However, the spatial specificity of MION is not well understood. In order to directly compare the spatial resolution of BOLD versus MION, we conducted a series of experiments in the anaesthetized macaque monkey preparation (macaca mulatta) at a magnetic field strength of 4.7 T. We acquired data using 8-segment multishot EPI with flip angle = 40 deg, TE = 20 ms, TR = 805 ms, for both BOLD and MION experiments. We typically injected 8mg/kg MION which is known to give near optimal CNR (Mandeville et al., 1998; Vanduffel et al., 2001). We measured the distribution of BOLD/MION as a function of gray matter depth in the primary visual cortex (V1) during stimulation with a full-field rotating polar checkerboard pattern alternating with uniform illumination (blank). Functional activation for MION peaked deeper in gray matter compared to BOLD, and appeared to sometimes even extend into white matter. To compare the extent of spatial activation of BOLD versus MION along the cortical surface, we used a rotating polar checkerboard pattern containing a 3.7○ diameter blank area we refer to as an ¨artificial scotoma¨. Functional activity spread inside the cortical area corresponding to the artificial scotoma (where there is no visual stimulation) appeared to be markedly greater for MION than for BOLD. On-going experiments aim to directly compare the fMRI findings to single unit responses inside the artificial scotoma.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {San Diego, CA, USA}, event_name = {34th Annual Meeting of the Society for Neuroscience (Neuroscience 2004)}, language = {en}, author = {Schmid, M and Tolias, AS and Augath, MA and Logothetis, NK and Smirnakis, SM} } @Poster { ShmuelAOPL2004_2, title = {Decreases in neuronal activity and negative BOLD response in non-stimulated regions of monkey V1}, journal = {Journal of Vision}, year = {2004}, month = {8}, volume = {4}, number = {8}, pages = {16}, abstract = {Background: 1. Numerous studies demonstrated that the response to a stimulus within the classical receptive field is modulated by an additional stimulus outside the receptive field. 2. A recent human fMRI study (Shmuel et al., Neuron 2002) demonstrated a robust sustained negative BOLD response (NBR) beyond the stimulated regions within retinotopic occipital areas. The NBR was associated with decreases in cerebral blood flow (CBF) and oxygen consumption, corroborating that the NBR could be triggered by decreases in neuronal activity. Aims: 1) Are there changes relative to spontaneous activity in non-stimulated regions in V1? 2) What are the neuronal correlates of the negative BOLD response? Methods: Monkeys were visually stimulated with iso-eccentricity rings of rotating checkers that subtended part of the visual-field (VF). A blank gray stimulus was used to measure the baseline cortical signal. Electrical recordings were obtained from the central VF representation in V1 simultaneously with fMRI. Results: Peripheral VF stimulus elicited positive/negative BOLD response in peripheral/more central VF representation in V1. The NBR was associated with decreases in neuronal activity (DsiNA), comparably large in action potentials, in the local-field potential and the multi-unit activity. DsiNA were observed up to 11 mm from the activated region in V1. The onsets of the increases and DsiNA were approximately concurrent, and the onset of the DsiNA preceded the corresponding onset of the NBR. Conclusions: 1) Non-stimulated regions adjacent to active regions in V1 decrease their neuronal activity. 2) The DsinNA cannot be exclusively mediated by the horizontal connections in V1. 3) The NBR in monkey V1 is associated with DsiNA that cannot be caused by hypoxia due to blood steal. 4) Most plausibly, the DsiNA trigger reductions in CBF that cause the NBR.}, department = {Department Logothetis}, web_url = {http://www.journalofvision.org/content/4/8/16.abstract}, event_place = {Sarasota, FL, USA}, event_name = {Fourth Annual Meeting of the Vision Sciences Society (VSS 2004)}, DOI = {10.1167/4.8.16}, author = {Shmuel, A and Augath, M and Oeltermann, A and Pauls, J and Logothetis, NK} } @Poster { SchmidTALS2004, title = {Spatial resolution of BOLD versus MION in a macaque fMRI paradigm at 4.7 T}, journal = {NeuroImage}, year = {2004}, month = {6}, volume = {22}, number = {Supplement 1}, pages = {e2449-2450}, abstract = {Most macaque functional magnetic resonance imaging (fMRI) studies are based on monitoring the intrinsic blood oxygen level dependent signal (BOLD) or, alternatively, on measuring changes in cerebral blood volume (CBV) after injection of a contrast agent. The intravascular contrast agent MION (monocrystalline iron oxide nanoparticles) has been recently applied in a number of studies (Dubowitz et al., 2001; Leite et al., 2002; Mandeville et al., 1997; Mandeville et al., 1998; Mandeville and Marota, 1999; Tsao et al., 2003a; Tsao et al., 2003b; Vanduffel et al., 2001). In comparison to BOLD, imaging with MION results in higher contrast to noise ratios (CNR) (Leite et al., 2002;Vanduffel et al., 2001) which may provide improved fMRI sensitivity, making MION especially appealing at low to moderate magnetic field strengths. Moreover, it has been suggested that MION may result in improved spatial specificity, since it appears to arise primarily from small parenchymal vessels (Mandeville et al., 1998; Mandeville and Marota, 1999) as opposed to BOLD which, at low magnetic fields, is known to be influenced by larger vessels that run along the cortical surface (Gati, Menon, et al., 1997). In order to directly compare the spatial resolution of BOLD versus MION, we conducted a series of experiments in the anaesthetized macaque monkey preparation (macaca mulatta) at a magnetic field strength of 4.7 T. We acquired data using 8-segment multishot EPI with flip angle = 40 deg, TE = 20 ms, TR = 805 ms, for both BOLD and MION experiments. We typically injected 8mg/kg MION which is known to give near optimal CNR (Mandeville, Marota, et al., 1998; Vanduffel, Fize, et al., 2001). In a first set of experiments we measured the distribution of BOLD/MION as a function of gray matter depth in macaque primary visual cortex (V1). Stimulation was done by alternating a rotating polar checkerboard with a field of uniform light intensity. Voxel size was 0.2 x 0.2 x 1mm 3 . Correlation coefficients were computed voxel by voxel and then averaged for voxels lying at the same cortical depth. Figure 1 plots the average correlation coefficients for BOLD (blue) versus MION (red) as a function of depth in the primary visual cortex (V1) of one macaque. Note that the correlation coefficients for MION appear to peak deeper in gray matter as compared to BOLD. To compare the spatial extent of functional activation seen with BOLD versus MION along the cortical surface, we used a similar stimulation paradigm as before, except that now the rotating polar checkerboard pattern contained a 6 deg diameter occluder (artificial scotoma) centered at 6 deg from the fovea. This assured that the corresponding cortical area in V1 received no direct visual stimulation. Figure 2 shows the correlation maps obtained with BOLD and MION under these stimulation conditions in a slice through the left V1 of one macaque (voxel resolution: 1 x 1 x 2 mm 3 ). Note that the spread of functional activity into the cortical area corresponding to the artificial scotoma (i.e. where there is no visual stimulation) appears to be markedly greater for MION than for BOLD.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science/article/pii/S1053811905700203}, event_place = {Budapest, Hungary}, event_name = {Tenth Annual Meeting of the Organization for Human Brain Mapping (HBM 2004)}, DOI = {10.1016/S1053-8119(05)70020-3}, author = {Schmid, MC and Tolias, AS and Augath, MA and Logothetis, NK and Smirnakis, SM} } @Poster { SultanATL2003, title = {Mapping visually activated cerebellar regions in anaesthetised monkeys with fMRI}, year = {2003}, month = {11}, volume = {33}, number = {74.8}, abstract = {Visual input handed over to the cerebellum by way of the pontine nuclei plays a crucial role in the sensory guidance of movement in primates (Stein and Glickstein, Physiol. Rev., Vol. 72, 1992). Based on the demonstration of visual single unit activity and the results of tract tracing experiments, several cerebellar regions seem to be involved in the processing of visual signals. The list of cerebellar areas implicated in the processing of visual information comprises vermal lobules VI, VII, VIII and IX, the hemispheric lobules crus I, dorsal paraflocculus and flocculus. Although already long, this list may still not be complete. We therefore looked for visually evoked cerebellar BOLD activation with a vertical 4.7 Tesla MRI scanner in monkeys. This approach provides us with a direct visualisation of the complete multisynaptic cerebro-ponto-cerebellar pathway. Monkeys were scanned while being anaesthetised in order to rule out movement-related BOLD responses, induced by the visual stimuli. In a first set of experiments we looked for cerebellar BOLD responses, evoked by moving large field random dot kinematograms. Our preliminary results indeed suggest that some of the previously proposed cerebellar regions are activated by such pure visual stimulus. More detailed studies may enable us to further dissect these regions as to their differential preferences for different visual stimuli.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/index.aspx?pagename=annualmeeting_futureandpast}, event_place = {New Orleans, LA, USA}, event_name = {33rd Annual Meeting of the Society for Neuroscience (Neuroscience 2003)}, author = {Sultan, FR and Augath, M and Thier, P and Logothetis, NK} } @Poster { 4502, title = {Simultaneous electrical microstimulation and fMRI in the macaque}, year = {2003}, month = {11}, volume = {33}, number = {69.20}, abstract = {Electrical microstimulation has been used extensively to study both neuronal connectivity and the behavioral effects of focal neural excitation. Yet most behaviors involve concurrent activation of several structures that are directly or indirectly interconnected with the stimulated site. Microstimulation performed simultaneously with fMRI offers a unique opportunity to investigate the network of structures eliciting certain behaviors. Recently, simultaneous recording of neural activity and BOLD responses in the monkey has been developed to study the correlation between the fMRI signals and electrical activity in the brain (Logothetis et al., 2001). This work has also enabled us to carry out simultaneous electrical microstimulation and fMRI. The specific goal of the current study is to determine the electrical parameters which elicit activity in the brain similar to that generated by focal visual stimulation. We compared visual stimulation with constant-current charge-balanced biphasic electrical pulses delivered via monopolar microelectrodes placed in area V1. We find that under certain microstimulation parameters we obtain focal activity around the electrode tip in area V1 as well the corresponding retinotopic location in area V2, V3, and MT. Ongoing research examines the activity patterns elicited by stimulating at different cortical layers of V1. This study paves the way to incorporate the much needed anatomical information in the analysis of the electrical signals obtained in trained, awake animals.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/index.aspx?pagename=annualmeeting_futureandpast}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {New Orleans, LA, USA}, event_name = {33rd Annual Meeting of the Society for Neuroscience (Neuroscience 2003)}, language = {en}, author = {Tolias, AS and Augath, M and Pauls, J and Oeltermann, A and Tehovnik, EJ and Schiller, PH and Logothetis, NK} } @Poster { FustPAOML2003, title = {The influence of anaesthetic agents on spiking and subthreshold activity in visual cortex revealed by electrophysiology and high-resolution functional MRI}, year = {2003}, month = {11}, volume = {33}, number = {69.14}, abstract = {The state of unconsciousness during anaesthesia is not characterized by a global disruption of CNS activity. Instead consciousness is mediated by a specific subset of brain states or processes selectively affected by anaesthetics. Our aim is to study the action sites of different types of anaesthetics in the monkey brain (M. mulatta). Here we report on the neural effects of Ketamine, a dissociative anaesthetic acting primarily on the NMDA receptor, and Midazolam, a benzodiazepine affecting GABA(A)-receptors. Ketamine exhibits both inhibitory and excitatory effects at different brain sites. Midazolam, however, is known to increase the GABA(A)-receptor function, and therefore to inhibit cortical activity. To study the primary sites-of-action of these agents in the monkey brain, high-resolution functional magnetic resonance imaging (fMRI) was used to measure stimulus induced activity changes in the alert and anaesthetized monkey. The activity of neurons in visual cortex was recorded during scanning, as well as in separate experiments outside the scanner. Following the acquisition of base-line data, a bolus of the test-substance was applied intravenously via a computerized infusion pump. Brain activity was monitored continuously before, during and after the infusion. The data presented here focus on the effects of anaesthetics on subthreshold and spiking activity and the BOLD-signal. A comparison of the influences on these different neural signals allows studying the site and type of action of anaesthetics in more detail. In addition it has the potential to afford further insights into the neural processes underlying the BOLD-signal.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/index.aspx?pagename=annualmeeting_futureandpast}, event_place = {New Orleans, LA, USA}, event_name = {33rd Annual Meeting of the Society for Neuroscience (Neuroscience 2003)}, author = {Fust, A and Pauls, J and Augath, M and Oeltermann, A and Murayama, Y and Logothetis, NK} } @Poster { 2406, title = {The Negative BOLD Response in Monkey V1 is Associated with Decreases in Neuronal Activity}, year = {2003}, month = {11}, volume = {33}, number = {125.1}, abstract = {Negative BOLD responses (NBRs) are pervasive in human fMRI, but commonly ignored. A recent study (Shmuel et al., Neuron 2002) characterized a robust sustained NBR in the human occipital cortex associated with decreases in cerebral blood flow (CBF) and oxygen consumption, corroborating that the NBR could be triggered by decreases in neuronal activity (DsiNA). Aims 1) Is the NBR associated with DsiNA? 2) Is the origin of the DsiNA vascular (e.g. from hypoxia due to blood steal) or neuronal? Monkeys were visually stimulated with iso-eccentricity rings composed of rotating checkers. A blank gray stimulus was used to measure the baseline cortical signal. Similar to the findings in humans, NBR was observed in monkeys: 1) in V1, V2, and V3, 2) in response to stimulation of part of the visual-field (VF), and 3) with a time course anti-correlated to that of the PBR. To determine the neuronal correlates of the NBR, electrical recordings were obtained from the central VF representation in V1 simultaneously with fMRI. Central/peripheral VF stimulus elicited PBR/NBR in the vicinity of the electrode (Fig. 1). Note that: 1) the NBR was associated with DsiNA, 2) the onsets of the increases and DsiNA were approximately concurrent, and 3) the onset of the DsiNA preceded the corresponding onset of the NBR. The NBR was associated with comparable decreases in both the local-field potential and the multi-unit activity. Conclusions The NBR in monkey V1 is associated with DsiNA that could not be caused by blood steal. Most plausibly, the DsiNA trigger reductions in CBF that cause the NBR.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/index.aspx?pagename=annualmeeting_futureandpast}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {New Orleans, LA, USA}, event_name = {33rd Annual Meeting of the Society for Neuroscience (Neuroscience 2003)}, language = {en}, author = {Shmuel, A and Augath, M and Oeltermann, A and Pauls, J and Logothetis, NK} } @Poster { KourtziTAAL2003, title = {Integration of local features into global shapes: monkey and human fMRI studies}, journal = {Journal of Vision}, year = {2003}, month = {10}, volume = {3}, number = {9}, pages = {191}, abstract = {The perception of global visual shapes entails the integration of local image features into global configurations. Traditionally, the visual system is thought to be hierarchically organized in early visual areas (V1, V2, V3, V4) that are involved in the analysis of simple local features and higher visual areas (regions in the inferotemporal cortex) that are implicated in the processing of complex global shapes. We investigated the integration of local image features into global shapes across visual areas in the monkey and the human brain using fMRI. An adaptation paradigm was used, in which stimulus selectivity was deduced by changes in the course of adaptation of a pattern of randomly oriented elements. Accordingly, we observed stronger activity after adaptation when orientation changes in the adapting stimulus resulted in a collinear shape than a different random pattern. This selectivity to collinear shapes was observed not only in higher visual areas, but also in early visual areas where selectivity depended on the receptive field size. These findings suggest that unified shape perception in both monkeys and humans involves multiple visual areas that may integrate local elements to global shapes at different spatial scales.}, department = {Department B{\"u}lthoff}, department2 = {Department Logothetis}, web_url = {http://www.journalofvision.org/content/3/9/191.abstract}, event_place = {Sarasota, FL, USA}, event_name = {Third Annual Meeting of the Vision Sciences Society (VSS 2003)}, DOI = {10.1167/3.9.191}, author = {Kourtzi, Z and Tolias, AS and Altmann, CF and Augath, M and Logothetis, NK} } @Poster { 2038, title = {Functional MR imaging of the awake monkey in a novel vertical large-bore 7 Tesla setup}, year = {2003}, month = {7}, day = {13}, volume = {11}, number = {1781}, pages = {349}, abstract = {First fMRI results in the awake trained monkey (Macaca mulatta) using a novel vertical 7T/60cm MR system are reported. The setup was custom-designed for MR imaging of monkeys in upright position and simultaneous electrophysiological recording. Using fast gradients and optimized RF coils, the benefits of high magnetic field with increased signal and contrast-to-noise ratio are demonstrated in high-resolution anatomical and functional images.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/pdf2038.pdf}, department = {Department Logothetis}, web_url = {http://www.ismrm.org/03/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Toronto, Canada}, event_name = {11th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2003)}, author = {Pfeuffer, J and Pauls, J and Augath, MA and Steudel, T and Merkle, H and Logothetis, NK} } @Poster { 2405, title = {Negative BOLD Response Ipsi-lateral to the Visual Stimulus: Origin Is Not Blood Stealing}, journal = {NeuroImage}, year = {2003}, month = {6}, volume = {19}, number = {2 Supplement}, pages = {e570-e571}, abstract = {Negative BOLD responses (NBRs) are pervasive in human fMRI experiments, but commonly ignored. The NBR in the human occipital cortex, triggered by stimulating part of the visual-field, is correlated with reductions in cerebral blood flow (CBF) and with decreases in oxygen consumption (Shmuel et al., 2002). The findings from this human study corroborate contributions to the NBR by 1) a significant component of reduction in neuronal activity, and possibly 2) a component of hemodynamic changes independent of the local changes in neuronal activity (e.g. passive reduction in CBF, also termed ’vascular blood steal’, due to increased flow to nearby, more demanding areas). Shmuel et al. (2002) indicated that vascular steal cannot account for NBR ipsi-lateral to a one hemi-field visual stimulus. In an accompanying abstract we show that the NBR in monkey V1 is associated with decreases in neuronal activity.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science/article/pii/S1053811905700033}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {New York, NY, USA}, event_name = {Ninth Annual Meeting of the Organization for Human Brain Mapping (HBM 2003)}, DOI = {10.1016/S1053-8119(05)70003-3}, author = {Shmuel, A and Augath, MA and Rounis, E and Logothetis, NK and Smirnakis, SM} } @Poster { 2404, title = {The Negative BOLD Response in Monkey V1 Is Associated with Decreases in Neuronal Activity}, journal = {NeuroImage}, year = {2003}, month = {6}, volume = {19}, number = {2 Supplement}, pages = {e567-e568}, abstract = {Negative BOLD responses (NBRs; i.e. below baseline) are pervasive in human fMRI experiments, but commonly ignored. A recent study characterized a robust sustained NBR in the human occipital cortex, triggered by stimulating part of the visual-field (Shmuel et al., 2002). The NBR depends on the pattern of neuronal activity and is coupled to the positive BOLD response (PBR). The NBR is correlated with reductions in cerebral blood flow (CBF) and with decreases in oxygen consumption. The findings from this human study corroborate contributions to the NBR by 1) a significant component of reduction in neuronal activity and possibly 2) a component of hemodynamic changes independent of the local changes in neuronal activity.}, department = {Department Logothetis}, web_url = {http://www.sciencedirect.com/science/article/pii/S1053811905700033}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {New York, NY, USA}, event_name = {Ninth Annual Meeting of the Organization for Human Brain Mapping (HBM 2003)}, DOI = {10.1016/S1053-8119(05)70003-3}, author = {Shmuel, A and Augath, MA and Oeltermann, A and Pauls, J and Murayama, Y and Logothetis, NK} } @Poster { 1560, title = {Biological motion processing in the macaque-fMRI}, year = {2002}, month = {11}, volume = {32}, number = {353.9}, abstract = {Psychophysical and imaging studies in humans have demonstrated specialized mechanisms for the detection of biological motion. Studies in humans, however, are limited in the details of these mechanisms they can reveal. We used functional MRI in the anaesthetized macaque to identify the brain areas involved in the analysis of biological motion and thereby provide electrode-guidance to study these mechanisms in more detail. We used a human point-light walker and a scrambled walker. The latter has identical local motion signals to the intact walker, but its local signals do not combine to a figure of a walking human. In a block-design we alternated these stimuli with periods of no visual stimulation. We recorded the BOLD response in a 4.7T vertical scanner (Bruker, Inc) using gradient-recalled multi-shot multi-slice EPI sequences. 21 horizontal slices covered the whole brain. Voxels were 1x1x2mm, TE =20ms, TR=1058ms. The data were analysed in BrainVoyager (BrainInnovation, Inc). Both the intact walker and the scrambled walker significantly activated early visual areas V1, V2 and the motion areas V3 and MT. More interestingly, we also found activation of areas commonly associated with form analysis such as V4 and the mid-anterior STS. Apparently, these areas are equipped with the neural mechanisms to detect the typical pendular movement associated with biological motion. In our setup, however, the intact walker never activated these areas significantly more than the scrambled walker.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/annual-meeting/past-and-future-annual-meetings}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Orlando, FL, USA}, event_name = {32nd Annual Meeting of the Society for Neuroscience (Neuroscience 2002)}, language = {en}, author = {Krekelberg, B and Augath, M and Logothetis, NK} } @Poster { 1587, title = {Combined neurophysiology and fMRI in the awake monkey}, year = {2002}, month = {11}, volume = {32}, number = {325.6}, abstract = {Simultaneous intracortical recordings of neural activity (NA) and BOLD responses in the anaesthetized monkey (Logothetis et al,2001)demonstrated various degrees of correlation between the fMRI data and LFP,MUA and SUA. The present work is a further step in the study of the relationship of BOLD to NA in the behaving monkey in a vertical-bore 7T/60cm scanner equipped with a 38-cm gradient insert (80mT/m,130us, Bruker Inc.). The upright positioning of the animal used in every alert monkey laboratory was also chosen for fMRI to minimize discomfort in the monkeys, expedite their training process, and ensure longer cooperation during psychophysical testing. Here, the monkeys were first trained to perform a fixation task (Wurtz, 1969) using juice as a reward. Stimuli were presented through a fiber-optic system (Silent Vision, FL), and eye movements were measured with the iView eye tracking system (SensorMotoric Inst.,GmbH). During data acquisition suction of juice and body movements were prevented by using a number of pressure and motion sensors and by training the animal to remain relaxed during the observation period. MR-compatible plastic chambers and electrodes made of platinum-iridium coated with glass were used for intracortical recordings. Gradient-induced interference was compensated with custom-made electronics (Patent 01116436.5). Brief pulse stimulation with full-field patterns and small stimuli placed within the receptive field of each recording site was used to elicit cortical responses followed by a BOLD response. The correlation of BOLD to different frequency bands with different spatio-temporal stimulation patterns will be discussed.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/annual-meeting/past-and-future-annual-meetings}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Orlando, FL, USA}, event_name = {32nd Annual Meeting of the Society for Neuroscience (Neuroscience 2002)}, language = {en}, author = {Logothetis, NK and Augath, M and Oeltermann, A} } @Poster { 1916, title = {Cue-invariant 3-D shape representation in monkey cortex using fMRI}, year = {2002}, month = {11}, volume = {32}, number = {721.7}, abstract = {Previous work using fMRI in anesthetized monkeys investigating the representation of 3-D objects defined by moving random dots or static texture cues revealed the presence of a network of areas responsive to 3-D shape in occipital, temporal, parietal, and frontal cortex (Sereno et al., Neuron, 2002). The goal of the present study was to determine the amount of activation overlap for 3-D surface shape defined with 3 different cues by directly comparing activation for the same 3-D shapes in the same scanning session. Stimuli consisted of a set of 3-D surfaces defined by dynamic (random dots with motion parallax) and static (shading and contour) shape cues. Each shape defined by a particular cue was paired with a control stimulus consisting of a scrambled or disrupted cue gradient. The control stimuli contain the same local information as the original surfaces (motion--dot speed and direction; shading--luminance range and pattern; surface contour--line shape and size). However, the disruption of the cue gradient across the image diminishes or abolishes an impression of depth. Activation from a comparison of intact to control stimuli revealed regions of common activation (e.g., in superior temporal, intra-parietal, and arcuate sulci) for shape defined by the 3 different cues. Our results suggest a set of candidate areas in monkey cortex for cue-invariant 3-D shape processing.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/annual-meeting/past-and-future-annual-meetings}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Orlando, FL, USA}, event_name = {32nd Annual Meeting of the Society for Neuroscience (Neuroscience 2002)}, language = {en}, author = {Sereno, M and Augath, M and Logothetis, NK} } @Poster { 1561, title = {fMRI responses to visual shapes at different spatial scales}, year = {2002}, month = {11}, volume = {32}, number = {260.16}, abstract = {The aim of the study is to understand the perception of global shapes from local image features. Specifically, we tested the role of various visual areas that are characterized by neural populations with different receptive field size in the integration of local features into global shapes at different spatial scales. To this end, we used fMRI in the anesthetized monkey and employed an adaptation paradigm. The paradigm entails prolonged presentation of a stimulus, resulting in decreased fMRI response, after which a change in a stimulus dimension elicits rebound of activity. The magnitude of the rebound correlates with the selectivity of an area to the changed dimension. The adapting stimulus was a rectangular area filled with randomly oriented line segments, followed by one of three test stimuli: a pattern identical to the adapting stimulus; a pattern where 1/3 of the line segments changed orientation randomly; a pattern in which change of line segment orientation resulted in a colinear shape. Spatial scale was manipulated by changing the size and the distance between the line segments. Differential responses to colinear shapes and random patterns indicated areas (V1,V2/V3) with neural populations that are selective for the global configuration of shapes, rather than local features. Rebound was observed in peripheral and central V1 for collinear shapes at large and small scales respectively. These findings suggest, that in the processing of global shapes from local features different visual areas are involved at different spatial scales.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/annual-meeting/past-and-future-annual-meetings}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Orlando, FL, USA}, event_name = {32nd Annual Meeting of the Society for Neuroscience (Neuroscience 2002)}, language = {en}, author = {Kourtzi, Z and Tolias, AS and Augath, M and Logothetis, NK} } @Poster { 1921, title = {Macaque visual cortex reorganisation after homonymous retinal scotoma probed by fMRI}, year = {2002}, month = {11}, volume = {32}, number = {760.2}, abstract = {Visual cortex has the capacity to reorganize in response to changes in sensory input. Early studies of visual deprivation (Blakemore, Hubel, LeVay) suggested that stimulus driven reorganization occurs only during a critical period in early development. Recent electrophysiological studies (Gilbert, Kaas, Chino, Rosa, Heinen) suggest that the visual system of adult mammals may undergo significant reorganization after de-afferentiation. There is an ongoing debate regarding the nature and extent of this reorganization (Horton, DeAngelis). Here we describe measurements of cortical reorganization after inducing a 5-8o homonymous scotoma in the retinas of adult rhesus macaques with a photocoagulation laser (GYC-2000, NIDEK). We used 4.7T functional magnetic resonance imaging (fMRI) in the anesthetized macaque preparation (Logothetis et al., Nat Neurosci 1999) to track the changes in visual field maps in early cortical areas. FMRI is appealing as it is noninvasive, provides global coverage of the visual areas, and facilitates comparison with human studies. By comparing the activation patterns seen as a function of time after induction of the scotoma we aim to outline the temporal course of cortical reorganization. Preliminary results, based on one monkey, reveal a localized cortical region within V1 (\verb=~=1.2x2.5cm2) whose signal response is strongly diminished by the lesion. Further, it appears that the fraction of area V1 silenced by the scotoma changes in time.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/annual-meeting/past-and-future-annual-meetings}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Orlando, FL, USA}, event_name = {32nd Annual Meeting of the Society for Neuroscience (Neuroscience 2002)}, language = {en}, author = {Smirnakis, SM and Brewer, AA and Schmid, M and Tolias, AS and Augath, M and Inhoffen, W and Wandell, BA and Logothetis, NK} } @Poster { 1920, title = {Mapping Macaque Visual Cortex Organization with BOLD and MION fMRI}, year = {2002}, month = {11}, volume = {32}, number = {759.5}, abstract = {Our research aims to use high field (4.7T) functional magnetic resonance imaging (fMRI) to map changes in cortical organization as a function of time after de-afferenting part of the primary visual cortex by inducing homonymous retinal lesions (Smirnakis et al., Neuroscience 2002). In order to obtain detailed maps of cortical organization by fMRI it is essential to use a strategy that maximizes spatiotemporal resolution. The contrast agent monocrystalline iron oxide nanoparticle (MION) has recently been used in the rat (Mandeville et al., Magn Res Med 1998,99) as well as in the awake behaving macaque (W. Vanduffel et al., Neuron 2001) to increase the sensitivity of fMRI imaging as compared to imaging based on the blood oxygenation level dependent (BOLD) signal. It is unclear, however, to what degree the advantage persists at higher field strengths, as well as whether the spatiotemporal profile of the MION (blood volume) induced signal provides adequate resolution to map cortical organization. Here we looked at the benefit of MION versus BOLD at 4.7 Tesla in the anesthesized macaque preparation (Logothetis at al., Nat Neurosci 1999). Visual stimuli of various sizes were presented in block design against background illumination, as well as retinotopic mapping was performed, with and without MION. Preliminary results suggest that MION invariably increased the sensitivity of the technique at 4.7T, boosting the modulation of the signal by a factor of 3-7 above that seen with the BOLD. The effect of MION on the spatial resolution is under investigation.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/annual-meeting/past-and-future-annual-meetings}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Orlando, FL, USA}, event_name = {32nd Annual Meeting of the Society for Neuroscience (Neuroscience 2002)}, language = {en}, author = {Schmid, M and Smirnakis, SM and Tolias, AS and Augath, M and Logothetis, NK} } @Poster { 1586, title = {Sustained negative BOLD response in the monkey brain}, year = {2002}, month = {11}, volume = {32}, number = {759.6}, abstract = {n a previous fMRI study (Shmuel et al., HBM 2001), a robust sustained negative BOLD response (NBR) and blood flow response was detected in the human occipital cortex. Here we report on a sustained (different from the initial dip) NBR in areas V1, V2, and V3 of the macaque. Anesthetized monkeys were presented in 4 cycles with a rotating polar checker pattern (48 s) followed by a blank gray image (48 s). Fifteen axial slices were imaged (GE-EPI, 4.7 T, 0.750.752 mm, TR=.75 s, 6 s/volume). In response to stimulation at 0-10 eccentricity, a positive BOLD response (PBR) and NBR were observed within the central and peripheral visual representation, respectively. The NBR was found preferentially in gray matter and was spatially reproducible across subjects. The time course of the NBR and PBR (mean amplitude ratio 0.5) were similar, suggesting similar mechanisms. Initial results from simultaneous fMRI and electrophysiology demonstrated NBR in 3 regions where no robust changes in electrical activity occurred. We are currently pursuing additional fMRI-electrophysiology experiments. Discussion 1) Robust NBR exists in the monkey brain. 2) Since the activity in the periphery is not expected to increase, the NBR here is the result of a decrease in blood flow rather than increase in oxygen consumption.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/annual-meeting/past-and-future-annual-meetings}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Orlando, FL, USA}, event_name = {32nd Annual Meeting of the Society for Neuroscience (Neuroscience 2002)}, language = {en}, author = {Shmuel, A and Augath, M and Oeltermann, A and Logothetis, NK} } @Poster { 1924, title = {Using Glass Patterns and fMRI to identify areas that process global form in macaque visual cortex}, journal = {Journal of Vision}, year = {2002}, month = {11}, volume = {2}, number = {7}, pages = {285}, abstract = {We have used functional imaging methods to locate areas of the macaque brain involved in processing global form. For this purpose, natural objects are not ideal stimuli because their form-defining characteristics are difficult to isolate and control. Glass patterns, created by pairing each dot in a random texture with another at a specified spatial offset (Glass 1969, Nature), are useful because form is defined in patterns with identical local statistics purely by the global arrangement of dot pairs. Wilson et al (1997, VR) showed that concentric Glass patterns are processed more efficiently than other patterns, suggesting that there exist higher-order ‘grouping’ filters tuned to particular patterns of activation among local filters. We generated different Glass patterns (concentric, radial, translational, and random) and used these to activate visual cortex in anaesthetized monkeys. We measured the resulting BOLD fMRI signals in a 4.7T scanner; voxel volume was 0.5\(\times\)0.5\(\times\)2mm. We collected 13 horizontal slices of the entire brain using multi-shot T2* weighted gradient-recalled EPI sequences. All Glass patterns produced substantial BOLD activity in V1 and V2, and in favorable cases also in more anterior areas including V4. Further analysis suggested that despite their identical local statistics, different patterns produced different degrees of activation in some cortical areas, with concentric patterns usually producing greater activation than other patterns. This difference was most marked in anterior extrastriate cortical areas including V4, and suggests that these areas contain neurons selectively sensitive to different global forms.}, department = {Department Logothetis}, web_url = {http://www.journalofvision.org/content/2/7/285}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Sarasota, FL, USA}, event_name = {Second Annual Meeting of the Vision Sciences Society (VSS 2002)}, DOI = {10.1167/2.7.285}, author = {Tse, PU and Smith, MA and Augath, MA and Trinath, T and Logothetis, NK and Movshon, JA} } @Poster { 1552, title = {Visualizing global brain networks in the monkey using combined fMRI and electrophysiology}, year = {2002}, month = {11}, volume = {32}, number = {325.7}, abstract = {We developed a novel method to visualize neural networks of endogenous activity that contribute to the variability observed in electrophysiological and functional imaging experiments. We compared activity recorded from a single electrode in the visual cortex of anesthetized monkeys with the time course of simultaneously recorded fMRI measurements. The electrophysiological signal we used was the band limited power (BLP) signal of the local field potential (LFP), which we have previously shown to exhibit slow and highly coherent fluctuations over large cortical distances. Whole-brain EPI images were collected in a 4.7 T scanner, while electrical activity was monitored with a single intracortical electrode. The maxima of cross-covariation between the BLP at that electrode and blood oxygen level-dependent (BOLD) signals for each voxel (1x1x2mm) in the imaged volume were used to generate maps of brain regions that were functionally linked with the spontaneous fluctuations on the electrode. We found that electrical activity at a single site was highly correlated with voxels throughout the brain. While covariation magnitude was greatest near the electrode tip, it remained significant even in distant brain regions, with cortical and subcortical sites showing different covariation patterns. Albeit preliminary, these results suggest that the electrophysiologically measured spontaneous activity in the visual cortex may result from large-scale fluctuations in global brain networks.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/annual-meeting/past-and-future-annual-meetings}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Orlando, FL, USA}, event_name = {32nd Annual Meeting of the Society for Neuroscience (Neuroscience 2002)}, language = {en}, author = {Leopold, D and Augath, M and Logothetis, NK} } @Poster { 1562, title = {In vivo 1H Spectroscopy of the Caudate Nucleus in Macaca mulatta brain}, year = {2002}, month = {8}, volume = {19}, number = {377}, abstract = {The neostriatum is important for the control of movement and certain cognitive functions [1]. Loss of striatal neurons or degeneration of the dopaminergic nigrostriatal pathway leads to devastating neurologic disorders. Recent studies about the reduction of Parkinson symptoms in primats [2,3] demonstrate the value of in vivo study of striatal neurochemistry. Here we present a pilot MRS study in monkeys, in which we conducted in vivo measurements of metabolite concentrations of a 0.7cc voxel positioned in the caudate nucleus of a macaque monkey. Our general aim is to combine this methodology with other invasive techniques, such as microdialysis or electrophysiology in order to couple the macroscopic changes visualized with MRS with their underlying neurophysiological events.}, url = {http://www.kyb.tuebingen.mpg.de/fileadmin/user_upload/files/publications/pdf1562.pdf}, department = {Department Logothetis}, web_url = {http://www.esmrmb.org/index.php?id=/en/post_conference_information/2002/esmrmb_2002.htm}, series = {1}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Cannes, France}, event_name = {19th Annual Scientific Meeting of the ESMRMB 2002}, author = {Juchem, C and Augath, MA and Merkle, H and Logothetis, NK and Pfeuffer, J} } @Poster { PrauseSPATHL2002, title = {In Vivo MRI of Neuronal Connections in the Macaque Monkey}, year = {2002}, month = {5}, day = {21}, volume = {10}, number = {1219}, url = {http://www.kyb.tuebingen.mpg.defileadmin/user_upload/files/publications/ISMRM-2002-Prause.pdf}, department = {Department Logothetis}, web_url = {http://www.ismrm.org/02/}, event_place = {Honolulu, HI, USA}, event_name = {10th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2002)}, author = {Prause, B and Saleem, KS and Pauls, J and Augath, M and Trinath, T and Hashikawa, T and Logothetis, NK} } @Poster { 1063, title = {fMRI adaptation for visual forms in the monkey brain}, year = {2001}, month = {11}, volume = {31}, number = {399.11}, abstract = {The aim of the study is to understand how local image features are integrated into configurations that may represent visual forms. We used fMRI in the anesthetized monkey and employed an adaptation paradigm (sufficiently prolonged presentation of a stimulus resulting in decreased fMRI responses over time) to test the role of various visual areas into such an integration process. The stimuli consisted of target-shapes embedded in a background of randomly oriented lines. The target-shapes were defined by collinearly arranged lines of the same height and width as the background lines. Following the presentation of an adapting stimulus, three conditions were tested:(A)presentation of a pattern identical to the adapting stimulus, (B) presentation of the same target-shape as the adapting stimulus but embedded in a different background (i.e. the background lines were rotated 90 deg), and (C) presentation of a different target-shape (orientation-changes of target rather than background lines). The selection of these conditions was motivated by the hypothesis that increased responses in the test phase for a new pattern are likely to indicate areas with neural populations that are selective for the global configuration of shapes, rather than local features. Initial experiments show that the time course of the fMRI signal varies in different visual areas. Not surprisingly, early visual areas failed to show shape selective adaptation, suggesting that the neural populations in these areas primarily encode local features. Differences in the time course of adaptation in higher visual areas are currently studied using a variety of visual patterns.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/index.aspx?pagename=abstracts_ampublications}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {San Diego, CA, USA}, event_name = {31st Annual Meeting of the Society for Neuroscience (Neuroscience 2001)}, language = {en}, author = {Kourtzi, Z and Tolias, AS and Prause, BA and Augath, M and Trinath, T and Logothetis, NK} } @Poster { 1067, title = {In vivo study of connectivity with electrical microstimulation and fMRI}, year = {2001}, month = {11}, volume = {31}, number = {783.5}, abstract = {We describe a new method that combines microstimulation with fMRI for the detailed study of neural connectivity in the alive animal. We used specially constructed microelectrodes to stimulate directly a selected subcortical or cortical area while simultaneously measuring changes in brain activity, indexed by the blood oxygen level dependent (BOLD) signal. The exact location of the stimulation site was achieved by means of anatomical scans as well as by the study of the physiological properties of neurons. Imaging was carried out in a Biospec 4.7T/40 cm vertical bore scanner (Bruker, Inc), using pulse sequences described elsewhere (Logothetis et. al. Nature Neuroscience 1999). Electrical stimulation was delivered using a biphasic pulse generator attached to a constant-current stimulus isolation unit. Constant-current charge-balanced biphasic pulses (300usec, 50 to 150 uA, at 50 to 500 Hz) were delivered to the brain for 12.5 sec preceded and followed by 12.5 and 39 sec respectively. The compensation circuit, designed to minimize interference generated by the switching gradients during recording, was always active alleviating all gradient-induced currents in the range of the stimulation current. Local microstimulation of striate cortex yielded both local BOLD signals and activation of areas V2, V3, and MT. Microstimulation of dLGN resulted in the activation of striate cortex, as well as areas V2, V3, and MT. Our findings show that microstimulation combined with fMRI can be exquisitely used to find and study target areas of regions of electrophysiological interest.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/index.aspx?pagename=abstracts_ampublications}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {San Diego, CA, USA}, event_name = {31st Annual Meeting of the Society for Neuroscience (Neuroscience 2001)}, language = {en}, author = {Logothetis, NK and Pauls, J and Oeltermann, A and Augath, M and Trinath, T} } @Poster { 1066, title = {Magnetic resonance imaging of neuronal connections in the macaque monkey}, year = {2001}, month = {11}, volume = {31}, number = {783.4}, abstract = {To date neuroanatomical connections have been mainly examined by means of degeneration methods and tracing techniques. Such studies require fixed processed tissue for the data analysis, and therefore they cannot be applied on the live animal. In the present study, we examined the neuronal connections in-vivo, particularly the output connections of striatum using MRI visible contrast agent (MnCl2) that is transported anterogradely through the axon, and subsequently trans-synaptically. MnCl2 (0.8 M) was injected into the caudate nucleus, and putamen in two rhesus monkeys. After the injection, the axonal transport of MnCl2 was continuously monitored for 24 hr or 45 hr using a 4.7T Biospec (Bruker, Inc) NMR scanner. We found a clear signal enhancement in the external and internal segments of the globus pallidus (Gpe and Gpi, respectively), and the substantia nigra, 24h after MnCl2 injection into the head of the caudate nucleus or putamen. Consistent with the previous anatomical studies, the spatial distribution of MnCl2 signal in globus pallidus, was different between caudate and putamen injections, with the former resulting in tracer accumulation in the dorsomedial, and the latter in the ventrolateral portion of the Gpe and Gpi. These findings were also confirmed histologically after WGA-HRP injection into the same region of the caudate or putamen, where the MnCl2 was injected. In addition, we found a strong signal increase in the thalamus and the cortical areas, particularly prefrontal and ventral inferotemporal areas, 45h after striatal injection. In conclusion, the tracer can be used to visualize neural networks with MRI.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/index.aspx?pagename=abstracts_ampublications}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {San Diego, CA, USA}, event_name = {31st Annual Meeting of the Society for Neuroscience (Neuroscience 2001)}, language = {en}, author = {Saleem, KS and Prause, BA and Pauls, J and Augath, M and Trinath, T and Hashikawa, T and Logothetis, NK} } @Poster { 1059, title = {Using glass patterns and fMRI to identify areas that process global form in macaque visual cortex}, year = {2001}, month = {11}, volume = {31}, number = {286.6}, abstract = {The goal of these experiments is to locate areas of the macaque brain involved in processing global form. For this purpose, natural objects are not ideal stimuli because their form-defining characteristics are difficult to isolate, parameterize, or control. Glass patterns, created by pairing each dot in a random texture with another at a specified spatial offset (Glass 1969, Nature), are useful because form is defined by the global statistics of dot placement with spatial correlations that are purely local. Recently, Wilson et al (1997, Vision Research) showed that concentric Glass patterns are processed more efficiently than other patterns with the same local but differing global statistics, suggesting that there exist higher-order ‘grouping‘ filters tuned to particular patterns of activation among local filters. We generated static and dynamic Glass patterns with different global forms, and used these to activate visual cortex in anesthetized monkeys. We measured the resulting BOLD fMRI signals in a 4.7T/40cm Biospec vertical scanner (Bruker, Inc), with 50mT/m gradients, using quadrature transmit/receive RF coils. Voxel volume was 0.5x0.5x2mm, TE=20ms, TR=750ms, and FA=40deg. We collected multi-shot, multi-slices T2* weighted images (13 horizontal slices) of the entire brain using gradient-recalled EPI fMRI sequences. We found significant signal differences between coherent Glass patterns and randomly oriented dot pairs in V2 and other areas. This suggests that grouping mechanisms and filters tuned to global form relationships among dots are located in these areas, but not in V1.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/index.aspx?pagename=abstracts_ampublications}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {San Diego, CA, USA}, event_name = {31st Annual Meeting of the Society for Neuroscience (Neuroscience 2001)}, language = {en}, author = {Tse, PU and Smith, MA and Augath, M and Trinath, T and Logothetis, NK and Movshon, JA} } @Poster { 4511, title = {Computations by networks of neurons: fMRI adaptation studies in monkeys}, year = {2001}, month = {3}, abstract = {A great deal is understood about the properties of single neurons processing visual information. In contrast, less is known about the collective characteristics of networks of cells that may underlie sensory capacities of animals. By measuring the blood oxygenation level-dependent (BOLD) signal in the macaque cortex we studied the emergent properties of populations of neurons processing motion across different brain areas. We used a visual adaptation paradigm to localize a distributed network of visual areas which process information about direction of motion, and also studied the dynamics of adaptation of the bold signal elicited by moving stimuli. We found that the BOLD signal in areas MT and V2/V3 adapted faster than in V1 reflecting the difference in motion processing between these areas. Moreover, the strength of the directionally selective bold signal in V1 was much greater than the one estimated on the basis of established facts from single cell electrophysiology. We propose an hypothesis that may account for this difference based on the postulate that neuronal selectivity is a function of the state of adaptation and therefore neurons classically thought to lack information about certain attributes of the visual scene, may nevertheless receive and process this information. The implementation of this hypothesis can arise as a result of intra- and inter-area cellular connections, such as feedback from higher areas. This network property may be a universal principle whose computational goal is to enhance the ability of neurons in earlier visual areas to adapt to statistical regularities of the input and therefore increase their sensitivity to detect changes along these stimulus dimensions.}, department = {Department Logothetis}, web_url = {http://zadorlab.cshl.edu/NIC.html}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Big Sky, MT, USA}, event_name = {Neural Information and Coding Workshop (NIC 2001)}, language = {en}, author = {Tolias, AS and Smirnakis, SM and Augath, M and Trinath, T and Logothetis, NK} } @Poster { 1042, title = {Effects of image coherence on the activity of posterior visual areas: an fMRI study}, year = {2000}, month = {11}, volume = {30}, number = {448.14}, abstract = {Natural images have a characteristic 1/f a power spectrum (Field, 1985). Different natural images thus differ mostly in their phase, and their spatial structure (e.g. edges) results in correlated phase spectra. Our aim was to study how processing in visual cortex varies as a function of phase correlation. To do this, we generated random phase spectra and performed linear interpolation between these random spectra and phase spectra of natural images. By using different interpolation levels (0\%,25\%,50\%,75\%,100\% signal), we could parametrically investigate the effects of phase correlation on the activity in visual areas, while keeping the power spectrum constant. Images were 10\(^{\circ}\)\(\times\)10\(^{\circ}\) in size, and were presented at randomized locations within ±3\(^{\circ}\) of the center of gaze to mimick saccadic eye movements. To study such effects by means of BOLD imaging, multi-shot (8) horizontal GE-recalled EPI images (voxel volume 0.5\(\times\)0.5\(\times\)2mm3, TE=20, TR=740, FA=50) of the entire brain of anesthetized monkeys were obtained using a Biospec 4.7T/40cm scanner (Bruker, Inc.) with 50mT/m gradients. This preparation affords the unique opportunity to examine activity in many brain areas simultaneously independent of cognitive factors, and provides a baseline to which human and awake monkey fMRI data on object processing may be compared. We found that many voxels were activated by natural images and/or interpolated patterns. Activity in striate and extrastriate cortical areas was modulated by interpolation level, with natural objects at 100\% signal typically eliciting most activity. We plan to examine the effects of varying power spectra (i.e. values of a) on the BOLD signal.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {New Orleans, LA, USA}, event_name = {30th Annual Meeting of the Society for Neuroscience (Neuroscience 2000)}, language = {en}, author = {Rainer, G and Augath, M and Trinath, T and Logothetis, NK} } @Poster { 1040, title = {Functionally linked neuronal assemblies: fMRI adaptation studies in monkeys}, year = {2000}, month = {11}, volume = {30}, number = {448.13}, abstract = {A great deal is known about the properties of single neurons processing visual information. In contrast, less is known about the collective properties of contiguous or distributed neuronal assemblies that may underlie sensory or perceptual capacities of animals. We are studying the activation properties of functionally linked neural populations using fMRI adaptation experiments. Using this paradigm we have investigated the spatial distribution of motion-induced neural activity in cortical and subcortical visual structures in anesthetized monkeys. A black and white foveally-centered rotating polar pattern was used, which consistently activated the LGN, V1 and extrastriate areas including area MT (Logothetis et al., 1999). During the first presentation phase, lasting a few minutes, the polar rotated in one direction (i.e. clockwise). Then, abruptly, the direction of rotation was reversed (second phase). The first phase was long enough for the fMRI signal to show adaptation. We hypothesize that activity in brain areas carrying direction of motion information increases immediately following the reversal due to release from adaptation to the opposite direction of motion, occurring prior to the reversal. Initial experiments, reveal that the time course of adaptation to rotating polar patterns can be monitored in several visual areas using fMRI. Preliminary results suggest that activity in several areas (cortical and subcortical) increased after the direction of motion reversal. These initial results suggest that the global-network properties of brain areas carry stimulus specific information beyond that typically measured in single unit recordings.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {New Orleans, LA, USA}, event_name = {30th Annual Meeting of the Society for Neuroscience (Neuroscience 2000)}, language = {en}, author = {Tolias, AS and Smirnakis, SM and Augath, M and Trinath, T and Logothetis, NK} } @Poster { 1050, title = {The relationship of LFPs, MUA, and SUA to the bold fMRI signal}, year = {2000}, month = {11}, volume = {30}, number = {309.5}, abstract = {The contribution of fMRI to our understanding of the functional anatomy of the brain is directly related to the degree to which the relationship between the MRI signal and the underlying neural activity is understood. It is established that activity in the brain is characterized by time-varying spatial distributions of action potentials superimposed on relatively slow-varying field potentials. To study how such potentials relate to the BOLD signal we scanned the visual cortex of anesthetized monkeys in a 4.7T scanner while recording local field potentials (LFPs), single (SUA), and multi (MUA) unit activity, by means of a novel, recently-developed recording technique. The geometry of novel electrodes and the active compensation built into the recording system minimized magnetic and electrostatic coupling respectively, permitting the elimination of any interference in subsequent off-line analysis. In each session, active sites were selected by first imaging the entire brain with a multi-shot, multi-slice gradient-recalled EPI MRI sequence (TE=20ms, TR=750ms), with FOV=128x128mm\verb=^=2,128\verb=^=2 matrix, 2mm thickness. Single slices, with areas of interest, were subsequently imaged with quadrature, transmit/receive volume or implanted surface coils with a voxel size of 250x250x660um\verb=^=3 using time-resolved MR imaging (TE=20ms, TR=250ms). Our results provide insights into (a) the relationship of slow waves, single unit activity, and coherence functions of simultaneously-recorded single-units to the BOLD signal; (b) the temporal response function of the signals, and (c) the effects of anesthesia depth and stimulus strength on the modulation of each signal-type.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {New Orleans, LA, USA}, event_name = {30th Annual Meeting of the Society for Neuroscience (Neuroscience 2000)}, language = {en}, author = {Logothetis, NK and Pauls, J and Oeltermann, A and Augath, M and Trinath, T} } @Poster { 1048, title = {The representation of 3-D shape in visual cortex: a monkey fMRI study}, year = {2000}, month = {11}, volume = {30}, number = {498.11}, abstract = {This study investigates how the visual system constructs representations of 3-D shape from a variety of cues using fMRI in anesthetized monkeys. A variety of computer-generated 3-D objects (e.g., geometrical shapes, faces, and other organic forms) defined by shading, random dots, texture elements, silhouetted, or as a wire frame were presented either statically, dynamically (i.e., rotating), or with stereo disparity. Control stimuli included constructed objects with scrambled cue gradients. Such stimuli contained the same local information as the original objects, but the disruption of the cue gradient across the image led to a loss of an impression of depth. Spatially resolved BOLD contrast-based functional images of monkey visual cortex were obtained using a hi-field (4.7 T) scanner and multi-shot, multi-slice, gradient-recalled, echo-planar imaging (EPI) sequences to image the brain (voxel volume, 0.5 \(\times\) 0.5 \(\times\) 2 mm3; TE=20 ms; TR=750 ms; FA=50 deg). Results showed significant activation in early visual areas, motion areas, and parts of the STS and IT cortex, suggesting involvement of multiple stages of processing of 3-D form starting in area V1 and continuing into the most anterior portions of the temporal lobe.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {New Orleans, LA, USA}, event_name = {30th Annual Meeting of the Society for Neuroscience (Neuroscience 2000)}, language = {en}, author = {Sereno, ME and Trinath, T and Augath, M and Logothetis, NK} } @Poster { 1051, title = {Tracking changes of stimulus coherence in macaque area it with fMRI}, year = {2000}, month = {11}, volume = {30}, number = {448.15}, abstract = {To study the time course of activation in different visual areas and the effects of increasing stimulus coherence in the activity of temporal cortices, a stimulus was generated that continuously transforms from one that has no globally recognizable form, into one that does. The stimuli appeared as fragmented images that show periodic increases and decreases in coherence through continuous rotation. In particular, we decomposed faces and objects into a ''bull‘s-eye'' pattern. Adjacent rings rotated in opposite directions, such that either a coherent face or object would come into phase for a brief duration. Imaging was performed in a 4.7T/40cm Biospec vertical scanner (Bruker, Inc), with 50mT/m gradients, using quadrature transmit/receive RF coils. Voxel volume was 0.5x0.5x2mm, TE=20ms, TR=740ms, and FA=20deg. Multi-shot, multi-slices T2* weighted images (15 horizontal slices) of the entire brain of anesthetized monkeys were collected using gradient-recalled EPI fMRI sequences. Areas that responded well to face or object stimuli were first localized using a standard block design. An optimal slice containing activated portions of both the occipital and temporal areas was then selected for a one-shot, (FOV=12.5, matrix=64x64 or 128x128) time-resolved imaging (TE=40ms, TR=250ms). Observation periods typically lasted 64 to 128 seconds permitting one or more full transitions from fragmented to fully coherent stimulus images. The time course of activation in different areas of the temporal pathway, its latency, as well as hysteresis and predictive activation effects will be discussed.}, department = {Department Logothetis}, web_url = {http://www.sfn.org/absarchive/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {New Orleans, LA, USA}, event_name = {30th Annual Meeting of the Society for Neuroscience (Neuroscience 2000)}, language = {en}, author = {Tse, PU and Augath, M and Trinath, T and Logothetis, NK} } @Poster { 1041, title = {fMRI on Primates with Custom Tailored RF Coils}, year = {2000}, month = {4}, day = {3}, volume = {8}, number = {1423}, pages = {143}, url = {http://www.kyb.tuebingen.mpg.defileadmin/user_upload/files/publications/ISMRM-2000-1423.pdf}, department = {Department Logothetis}, web_url = {http://www.ismrm.org/00prog/posters/poster49.htm}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Denver, CO, USA}, event_name = {8th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2000)}, author = {Merkle, H and Augath, MA and Trinath, T and Logothetis, NK and Ugurbil, K} } @Poster { 1451, title = {Customized RF coils and fMRI on primates}, journal = {Magnetic Resonance Materials in Physics, Biology and Medicine}, year = {1999}, month = {2}, volume = {8}, number = {Supplement 1}, pages = {207-208}, abstract = {Functional magnetic resonance imaging (fMRI) is now successfully established in nonhuman primates [1]. Due to its availability, fMRI is likely to complement or replace invasive physiological techniques in the near future. However. development of novel hard- and software is critical to maximize its usefulness in novel research applications. In this contribution, we report on the design and use of custom-tailored radio frequency coils for increased signal to noise in (t')images of the monkey brain.}, department = {Department Logothetis}, web_url = {http://www.springerlink.com/content/cw415v506v467r12/fulltext.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Sevilla, Spain}, event_name = {16th Annual Meeting of the European Society for Magnetic Resonance in Medicine and Biology (ESMRMB '99)}, DOI = {10.1007/BF02605952}, author = {Merkle, H and Trinath, T and Augath, MA and Logothetis, NK and Ugurbil, K} } @Conference { LogothetisEMASEBO2013, title = {Studying large-scale brain networks: electrical stimulation and neural-event-triggered fMRI}, journal = {BMC Neuroscience}, year = {2013}, month = {7}, volume = {14}, number = {Supplement 1}, pages = {1}, abstract = {The brain is ''the'' example of an adaptive, complex system. It is characterized by ultra-high structural complexity and 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. In the study of such systems one major problem is the adequate definition for an elementary operational unit (often called an ''agent''), because any such module can be a complex system in its own right and may be recursively decomposed into other sets of units. A second difficulty arises from the synergistic organization of complex systems and of the brain in particular. Synergy here refers to the fact that the behavior of an integral, aggregate, whole system cannot be trivially reduced to, or predicted from, the components themselves. Localizing and comprehending the neural mechanisms underlying our cognitive capacities demands the combination of multimodal methodologies, i.e. it demands concurrent study of components and networks; one way of doing this, is to combine invasive methods which afford us direct access to the brain's electrical activity at the microcircuit level with global imaging technologies such as magnetic resonance imaging (MRI). In my talk, I'll discuss two such methodologies: Direct Electrical Stimulation and fMRI (DES-fMRI) and Neural-Event-Triggered fMRI (NET-fMRI). DES-fMRI can be used in hopes of gaining insight into the functional or effective connectivity underlying DES-induced behaviors. Yet, our first findings suggest that DES has an important limitation: It clearly demarcates all monosynaptic targets of a stimulated site, but it largely fails to reveal polysynaptic cortico-cortical connectivity. NET-fMRI, on the other hand, appears to offer great potential for mapping whole-brain activity that is associated with individual local events. In the second part of my talk, I'll describe the characteristic states of widespread cortical and subcortical networks that are associated with the occurrence of hippocampal sharp waves and ripples; the brief aperiodic episodes associated with memory consolidation.}, department = {Department Logothetis}, department2 = {Department Sch{\"o}lkopf}, talk_type = {Keynote Lecture}, web_url = {http://www.biomedcentral.com/1471-2202/14/S1/A1}, event_place = {Paris, France}, event_name = {Twenty-Second Annual Computational Neuroscience Meeting (CNS*2013)}, DOI = {10.1186/1471-2202-14-S1-A1}, author = {Logothetis, NK and Eschenko, O and Murayama, Y and Augath, M and Steudel, T and Evrard, HC and Besserve, M and Oeltermann, A} } @Conference { ParkesHALP2010, title = {High resolution tractography in macaque visual system: validation against in vivo tracing}, year = {2010}, month = {5}, day = {3}, 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.}, url = {http://www.kyb.tuebingen.mpg.defileadmin/user_upload/files/publications/ISMRM-2010-118.PDF}, department = {Department Logothetis}, talk_type = {Abstract Talk}, web_url = {http://www.ismrm.org/10/}, event_place = {Stockholm, Sweden}, event_name = {ISMRM-ESMRMB Joint Annual Meeting 2010}, author = {Parkes, LM and Haroon, HA and Augath, M and Logothetis, NK and Parker, GJ} } @Conference { 4993, title = {Areas V2 and V3 remain active and retinotopically organized in the absence of direct V1 input}, year = {2007}, month = {11}, volume = {37}, number = {122.2}, abstract = {The presence of focal lesions in primary visual cortex (V1) provides an opportunity to study the role of extra-geniculo-striate pathways for activating extra-striate areas. Single unit measurements reported inactivation of more than 95\% of V2 and V3 neurons following reversible cooling of V1 (Girard and Bullier, 1989; Girard et al., 1991a; Schiller et al., 1974). Here we used fMRI in anesthetized monkeys (Logothetis et al., 1999) to study the organization and activation levels of areas V2 and V3 from one month up to 681 days following a focal V1 aspiration lesion. We find that the strength of stimulus driven BOLD activation inside the area V2, V3 lesion projection zones (LPZ) drops by \verb=~=70 \% compared to baseline and shows no systematic change between the first month post-lesioning and the maximum time studied. Interestingly, the retinotopic organization of the area V2, V3 LPZs remains similar to pre-lesion maps. Restricting the stimulus to the non-lesioned visual field is not effective in activating the ipsi-lesional LPZ ruling out the possibility that callosal input mediates the observed pattern of responses. We conclude that residual activity in V2 and V3 devoid of V1 input is likely due to parallel subcortical pathways possibly contributing to the behavioral phenomenon of blindsight. Figure Caption: Eccentricity map of the right visual cortex of a rhesus macaque 681 days post-V1 lesioning. Visual stimulation was performed using a rotating checkerboard ring stimulus (gray inset) expanding in time and space which resulted in a phase shift of the BOLD response (retinotopic mapping). Voxels with similar phase values are color-coded (colored inset) and superimposed on the anatomical flat map. The lesion in V1 extends from \verb=~=2.3 to 7\(^{\circ}\), and from the external calcarine to the lunate (total area: 235 mm²). The lesion projection zones (LPZ) of dorsal V2 and V3 are outlined using retinotopic correspondence criteria. Despite the absence of retinotopically}, department = {Department Logothetis}, talk_type = {Abstract Talk}, web_url = {http://www.sfn.org/annual-meeting/past-and-future-annual-meetings}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {San Diego, CA, USA}, event_name = {37th Annual Meeting of the Society for Neuroscience (Neuroscience 2007)}, language = {en}, author = {Schmid, MC and Panagiotaropoulos, T and Augath, MA and Logothetis, NK and Smirnakis, SM} } @Conference { 4997, title = {Microstimulation-evoked BOLD responses of the macaque cerebellar cortex}, year = {2007}, month = {11}, volume = {37}, number = {339.3}, abstract = {Imaging brain activity evoked by intracortical electrical stimulation with fMRI is proving to be a useful tool to study functional characteristics of the brains connectivity in vivo. Here we stimulated the cerebellar cortex with microelectrodes in the anaesthetized rhesus monkey. BOLD responses in the cerebellar cortex were easily evoked with currents of 250 µA (pulse duration: 200µs; frequency: 100Hz). The spatial spread of the BOLD response after stimulation in the anterior lobe (intermediate zone of Lobule IV and V) was large and extended well to the contralateral cerebellar side. Based on the well known connectivity of the cerebellum the spread of such a bilateral activation can be explained through an antidromic excitation of mossy fibres, since these are the only excitatory fibres that can extend bilaterally in the cerebellum. Mossy fibres originating from the lateral reticular nucleus (LRN), for instance have a substantial bilateral contribution (Pijpers et al., 2006) and project heavily to the vermal and intermediate zone of the lobus anterior. So far our stimulation of the posterior lobe (Crus II) on the other hand yielded largely ipsilateral cerebellar activation. This cerebellar region receives its mossy fibres mainly from the pontine nuclei which have a strong contralateral and a weak ipsilateral contribution, indicating a lesser degree of bilaterality. Cerebellar stimulation yielded a relatively larger spatial spread of BOLD responses than what we have previously observed after cerebral cortical extrastriate and striate stimulation. This is in contradiction to predictions based on the facts that cerebral cortex intraconnectivity is much more extended than the cerebellar short-range intracortical connections. Our observations indicate that this is either due to a larger bifurcation pattern of the cerebellar mossy fibres, or/and to lower thresholds for the activation of mossy fibres and for triggering metabolic changes. In summary, microstimulation-evoked BOLD responses of the cerebellar cortex reveals different patterns of connectivity within the cerebellum and points to some important functional characteristics of these connections.}, department = {Department Logothetis}, talk_type = {Abstract Talk}, web_url = {http://www.sfn.org/am2007/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {San Diego, CA, USA}, event_name = {37th Annual Meeting of the Society for Neuroscience (Neuroscience 2007)}, language = {en}, author = {Sultan, FR and Augath, M and Hammodeh, S and Oeltermann, A and Logothetis, NK} } @Conference { LogothetisSMASO2006, title = {Microstimulation and fMRI in anesthetized and alert monkeys: Conditions for transsynaptic BOLD activation}, year = {2006}, month = {10}, volume = {36}, number = {114.10}, abstract = {We have recently combined electrical stimulation and fMRI and demonstrated that the excitability properties of the directly stimulated elements in neocortex using this method are very similar to those obtained with either intracortical recordings or behavioral methods (Tolias et al., 2005). Microstimulation in cortical area V1 of the macaque activated mainly the pyramidal fibers, and the effective current spread, that was measured by means of the BOLD activation, was found to be greater than that obtained with the other two methods. Stimulation of V1 (and in later studies of MT), however, revealed mainly the monosynaptic targets of each stimulated region. Here we set out to elucidate the conditions for which transsynaptic effects can be obtained. Experiments were conducted in anesthetized and alert monkeys in a 4.7T/40cm and 7T/60 scanner, respectively. Electrical stimulation was delivered using a biphasic pulse generator attached to a constant-current stimulus isolation unit. Constant-current charge-balanced, band-limited pulses of different center frequency, pulse duration and current strength were delivered to the brain for periods of 4 sec preceded and followed by 4 sec and 12 sec blank periods, respectively. The compensation circuit, designed to minimize interference generated by the switching gradients during recording, was always active, alleviating all gradient-induced currents in the range of the stimulation current. Local microstimulation was applied in dLGN, pulvinar, striate and extrastriate cortex. The areas activated upon stimulation of each of these sites was found to depend primarily on the central frequency of the frequency band used. Transsynaptic activation also depended on stimulation condition. Differences between the anesthetized and alert monkey experiments will be discussed.}, department = {Department Logothetis}, talk_type = {Abstract Talk}, web_url = {http://www.sfn.org/index.aspx?pagename=abstracts_ampublications}, event_place = {Atlanta, GA, USA}, event_name = {36th Annual Meeting of the Society for Neuroscience (Neuroscience 2006)}, author = {Logothetis, NK and Sultan, F and Murayama, Y and Augath, M and Steudel, T and Oeltermann, A} } @Conference { SultanAOTL2006, title = {Microstimulation of the upper posterior bank of the STS}, year = {2006}, month = {10}, volume = {36}, number = {114.9}, abstract = {In the macaque the extrastriate area V5/MT is located within the dorsal half and on the posterior bank of the superior temporal sulcus. Neurons in V5/MT show directional tuning to moving stimuli. Furthermore, these neurons are organized in a retinotopic fashion with those responding to stimuli located at the center of gaze being more lateral and ventral within V5/MT (Gattass and Gross, 1981). We have now extended the technique of combined electrical microstimulation and fMRI from the striate cortex (Tolias et al., 2005) to this well-studied extrastriate region to further probe this technique as a tool to map the functional connectivity of the brain. We electrically stimulated V5/MT in the anaesthetized macaque in a 4.7T scanner with biphasic charge-balanced pulses (up to 1mA and 200us pulse width per phase) and evoked BOLD responses consistently in a number of brain areas known to be directly connected to V5/MT. BOLD responses were observed in ipsilateral V2, V3, V4, V4t, PO, MST, in the anterior and posterior banks of the IPS (corresponding to LIP) and in the superior colliculus. Two types of projection patterns could be discerned by stimulation of either the peripheral or the foveal retinal representation of area V5/MT. The latter showed activation of regions located on the lateral surface of the occipital cortex while the former showed activity in mesial occiptio-parietal cortex. BOLD responses were surprisingly rather difficult to evoke in V1 with our current stimulation paradigms. V1 responses were largely seen in peripheral V1 regions. This could indicate that the evoked BOLD responses are dominated by orthodromic vs antidromic pathway activation, however, electrical stimulation of the pulvinar in contrast to V5/MT evoked excellent BOLD responses in V1. Since the V1-pulvinar connectivity is mainly feedforeward, this then proves that antidromic pathway activation is well detected by our method. Hence the different activation patterns that we observe in V1 after MT/V5 and pulvinar stimulation are rather related to the different pathways characteristics, possibly related to differences in the type of synaptic connectivity. Thus microstimulation combined with fMRI may well prove to be a novel technique suited to reveal different characteristics of the brains functional connectivity.}, department = {Department Logothetis}, talk_type = {Abstract Talk}, web_url = {http://www.sfn.org/index.aspx?pagename=abstracts_ampublications}, event_place = {Atlanta, GA, USA}, event_name = {36th Annual Meeting of the Society for Neuroscience (Neuroscience 2006)}, author = {Sultan, FR and Augath, M and Oeltermann, A and Tolias, AS and Logothetis, NK} } @Conference { PetkovKASL2005, title = {High-Field fMRI Reveals Auditory Cortical Fields in the Macaque Monkey}, year = {2005}, month = {11}, day = {11}, department = {Department Logothetis}, department2 = {Research Group Kayser}, talk_type = {Abstract Talk}, web_url = {http://www.apan.jhu.edu/Program_APANIII.htm}, event_place = {Washinton, DC, USA}, event_name = {Tucker-Davis Symposium on Advances and Perspectives in Auditory Neurophysiology (APAN III)}, author = {Petkov, CI and Kayser, C and Augath, M and Steudel, T and Logothetis, NK} } @Conference { SerenoAL2005, title = {Differences in processing of 3-D shape from multiple cues in monkey cortex revealed by fMRI}, year = {2005}, month = {11}, volume = {35}, number = {362.9}, abstract = {Previous work using fMRI in anesthetized monkeys to investigate the representation of 3-D objects and surfaces suggests a set of candidate areas in monkey cortex for cue-invariant 3-D shape processing (Sereno et al., Neuron, 2002). The present study examines activation overlap for 3-D surface shape defined with 3 different cues by directly comparing activation for the same 3-D shapes in the same monkey subjects. Stimuli consisted of a set of 3-D surfaces defined by dynamic (random dots with motion parallax) and static (shading and contour) shape cues. Each shape defined by a particular cue was paired with a control stimulus consisting of a scrambled or disrupted cue gradient to diminish or abolish an impression of depth. Activation from a comparison of intact to control stimuli revealed regions of common activation (e.g., in superior temporal and intra-parietal sulci) for shape defined by the 3 different cues. However, significant differences between the dynamic and static cues emerged. The extent and strength of activation was greater in area MT for dynamic compared to static cues; whereas the opposite was true in area V4. In addition, while there was significant overlap across the cues in regions of the STS anterior to area MT (FST and mid-anterior STS), in each of these regions there was a greater number of voxels active for shape-from-motion stimuli in the fundus vs. the more lateral aspect of the ventral bank. In turn, the lateral aspect of the ventral bank had a greater number of voxels active for shape-from-shading and -contour compared to shape-from-motion stimuli. Between the regions activated primarily by dynamic or static cues there was a region of convergence activated by all the cues.}, department = {Department Logothetis}, talk_type = {Abstract Talk}, web_url = {http://www.sfn.org/absarchive/}, event_place = {Washington, DC, USA}, event_name = {35th Annual Meeting of the Society for Neuroscience (Neuroscience 2005)}, author = {Sereno, ME and Augath, M and Logotethis, NK} } @Conference { ShmuelAOPL2004, title = {Linking the negative BOLD response to decreases in neuronal activity in monkey V1}, year = {2004}, month = {10}, day = {23}, volume = {34}, number = {18.14}, abstract = {Previously we demonstrated that the negative BOLD response (NBR) in non-stimulated regions of V1 is associated with decreases in neuronal activity (DsiNA), and that the DsiNA cannot be caused by hypoxia due to the associated negative cerebral blood flow (CBF) response. DsiNA were observed 11 mm away from the stimulated region; thus they cannot be exclusively mediated by the horizontal connections. Aims 1) Are the NBR and DsiNA independent or coupled phenomena? 2) Does the NBR reflect decreases in synaptic or in spiking activity? Monkeys were stimulated visually with rotating checkers. Electrical recordings were obtained simultaneously with fMRI. Peripheral visual-field (VF) stimuli elicited PosBR/NBR in peripheral/more central VF representations in V1. The amplitude of the NBR measured across single trials was correlated with the corresponding amplitude of the DsiNA within single sessions (p<0.0001). The NBR was correlated with the amplitudes of decreases in the comprehensive neuronal signal, LFP, MUA, and action potentials (APs) of single neurons. As expected, the variance of the time course of the PosBR could be better predicted by the variance of the LFP (r2=.69±.15, n=5 sessions) than by that of the MUA (r2=.57±.22) and the APs (r2=.52±.22). In contrast, the variance of the NBR could be comparably predicted using the decreases in LFP (r2=.59±.17), MUA (r2=.64±.10) or APs (r2=.60±.11). Similar DsiNA were observed outside of the scanner, ruling out the possibility of artifacts caused by electrical recordings simultaneously with fMRI. Conclusions 1) Non-stimulated regions adjacent to active regions in V1 decrease their neuronal activity. 2) The comparable decreases in LFP, MUA and APs are consistent with decreases in the input to the NBR region and/or suppression within the NBR region. 3) The findings corroborate a model in which the DsiNA trigger reductions in CBF that contribute significantly to the NBR.}, department = {Department Logothetis}, talk_type = {Abstract Talk}, web_url = {http://www.sfn.org/absarchive/}, event_place = {San Diego, CA, USA}, event_name = {34th Annual Meeting of the Society for Neuroscience (Neuroscience 2004)}, author = {Shmuel, A and Augath, M and Oeltermann, A and Pauls, J and Logothetis, NK} } @Conference { 4503, title = {V1 cortical reorganization revisited: fMRI and electrophysiology in macaque following retinal lesions}, year = {2004}, month = {10}, volume = {34}, number = {605.3}, abstract = {ntroduction. Electrophysiological studies (Chino, Calford, Heinen, Gilbert, Kaas, Rosa) suggest that adult V1 visual field maps reorganize after de-afferentiation. The reported electrophysiological reorganization appears inconsistent with cytochrome oxidase staining patterns after similar de-afferentiation (Horton \&amp; Hocking, J Neurosci 1998). We are measuring macaque V1 responses with functional magnetic resonance imaging (fMRI) and electrophysiology to clarify the extent of V1 reorganization. Methods. A retinal photocoagulation laser (GYC-2000, NIDEK) was used to lesion 5-8 degree homonymous visual field locations in four adult rhesus macaques. The retinal lesion creates a de-afferentiated V1 zone referred to as the lesion projection zone, or LPZ (Schmid et al., Cerebral Cortex 1996). As expected, following the lesion we found little or no response to visual stimulation inside the LPZ using functional magnetic resonance imaging (fMRI) at 4.7T in the anesthetized macaque preparation (Logothetis et al., Nat Neurosci 1999). The extent of V1 reorganization was quantified by repeatedly measuring the visual modulation in the BOLD signal near the border of the LPZ. Results. Over the course of seven months, we found very little, if any, increase in BOLD activity within the LPZ apart from that expected by reduced retinal swelling. The boundary of the LPZ remained stable to within 1 mm. The stable scotoma persisted in the BOLD response in all four animals tested. Parallel electrophysiological experiments are in progress in these animals, allowing direct comparison between BOLD measurements and single unit responses.}, department = {Department Logothetis}, talk_type = {Abstract Talk}, web_url = {http://www.sfn.org/absarchive/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {San Diego, CA, USA}, event_name = {34th Annual Meeting of the Society for Neuroscience (Neuroscience 2004)}, language = {en}, author = {Smirnakis, SM and Brewer, AA and Schmid, M and Tolias, AS and Augath, M and Inhoffen, W and Sch{\"u}z, A and Wandell, BA and Logothetis, NK} } @Conference { WadeALW2004, title = {Colour constancy and colour pathways in human and macaque}, journal = {Perception}, year = {2004}, month = {9}, volume = {33}, number = {ECVP Abstract Supplement}, pages = {25}, abstract = {Human functional neuroimaging experiments have identified a colour area on the ventral surface of occipital cortex. However, the precise function, location, and extent of this area are disputed as is its possible homology with macaque V4. The discovery of this area has also diverted attention from measurements in other parts of the colour pathways. We present two results from our humans and macaque neuroimaging work. (i) Measurements in V1 show that changes in the background cone absorption rate influence the response gain to a constant-amplitude probe stimulus. The response gain appears to be controlled separately within each of the cone classes. These gain changes are significant for colour constancy and appear to be localised in the retina. (ii) Macaque cortex shows strong responses to isoluminant colour both dorsally and ventrally in V2 and V4. In humans, the largest responses to the same stimuli are confined to the ventral surface anterior to V3v. These data indicate that colour signals are processed in a pathway beginning at the retina and extending well into extrastriate cortex. Colour constancy is refined at several stages along this pathway. Finally, there appear to be differences between the humans and macaque colour pathways.}, department = {Department Logothetis}, talk_type = {Abstract Talk}, web_url = {http://pec.sagepub.com/content/33/1_suppl.toc}, event_place = {Budapest, Hungary}, event_name = {27th European Conference on Visual Perception}, DOI = {10.1068/ecvp04a}, author = {Wade, A and Augath, M and Logothetis, NK and Wandell, BA} } @Conference { 2407, title = {The Negative BOLD Response in Monkey V1 is Associated with Decreases in Neuronal Activity}, year = {2003}, month = {7}, day = {13}, volume = {11}, number = {211}, pages = {51}, abstract = {This study aimed at revealing the neuronal correlates of the negative BOLD response (NBR). Electrical recordings were obtained from NBR regions in monkey V1 simultaneously with fMRI. The NBR was associated with a reduction in neuronal activity, both in the Multi-Unit-Activity and the Local-Field-Potential domains. The onset of the decrease in neuronal signal preceded the corresponding onset of the NBR, indicating that the origin of the NBR was a decrease in neuronal activity that triggered a reduction in CBF, rather than decreased neuronal activity caused by reduced CBF.}, department = {Department Logothetis}, talk_type = {Abstract Talk}, web_url = {http://www.ismrm.org/03/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Toronto, Canada}, event_name = {11th Scientific Meeting of the International Society of Magnetic Resonance in Medicine (ISMRM 2003)}, author = {Shmuel, A and Augath, MA and Oeltermann, A and Pauls, J and Logothetis, NK} } @Conference { 1056, title = {A network of areas for 3-D shape processing in the anesthetized monkey}, year = {2001}, month = {11}, volume = {31}, number = {122.4}, abstract = {Using fMRI in anesthetized monkeys and a variety of computer-generated 3-D objects defined by shading, random dots, texture elements, or silhouettes and presented either statically or dynamically (rotating), we have previously identified 3-D shape-specific areas in occipital (areas VP and V3) and temporal (areas MT and FST; mid-to-anterior STS; and the AMTS) cortices (Sereno et al., Soc. Neurosci. Abstr., 26, 498.11, 2000). The present study investigates representation of 3-D shape from motion parallax using dynamic random dots in brain regions beyond the occipital and temporal lobes. Control stimuli consist of constructed objects with scrambled motion gradients. Such stimuli contain the same local motion information as the original objects, but the disruption of the cue gradient across the image diminishes an impression of depth. Spatially resolved BOLD contrast-based functional images of monkey visual cortex were obtained using a high-field (4.7 T) scanner and multi-shot, multi-slice, gradient-recalled, echo-planar imaging (EPI) sequences (voxel size, 1 x1 x 2 mm). Results showed significant activation in previously identified shape-specific regions of occipital and temporal lobes but also several areas in the intraparietal sulcus and two frontal lobe regions (the FEF and ventrolateral prefrontal cortex). This distributed network of areas cuts across both ventral and dorsal processing streams, reflecting multiple uses for 3-D shape representation in perception, recognition, and action.}, department = {Department Logothetis}, talk_type = {Abstract Talk}, web_url = {http://www.sfn.org/index.aspx?pagename=abstracts_ampublications}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {San Diego, CA, USA}, event_name = {31st Annual Meeting of the Society for Neuroscience (Neuroscience 2001)}, language = {en}, author = {Sereno, MA and Augath, M and Trinath, T and Logothetis, NK} }