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

@Article{ 5201,
title = {Crossmodal Propagation of Sensory-Evoked and Spontaneous Activity in the Rat Neocortex},
journal = {Neuroscience Letters},
year = {2008},
month = {2},
volume = {431},
number = {3},
pages = {191-196},
abstract = {In the cortex, neural responses to crossmodal stimulation are seen both in higher association areas and in primary sensory areas, and are thought to play a role in integration of crossmodal sensations. We used voltage-sensitive dye imaging (VSDI) to study the spatiotemporal characteristics of such crossmodal neural activity. We imaged three cortical regions in rat: primary visual cortex (V1), barrel field of primary somatosensory cortex (S1bf) and parietal association area (PA, flanked by V1 and S1bf). We find that sensory-evoked population activity can propagate in the form of a distinct propagating wave, robustly in either crossmodal direction. In single trials, the waveforms changed continuously during propagation, with dynamic variability from trial to trial, which we interpret as evidence for cortical involvement in the spreading process. To further characterize the functional anatomy of PA, we also studied the propagation of spontaneous sleep-like waves in this area. Using a novel flow-detection algorithm, we detected a propagation bias within PA of spontaneous waves—these tend to propagate parallel to the crossmodal axis, rather than orthogonal to it. Taken together, these findings demonstrate that intracortical networks show pre-attentive crossmodal propagation of activity, and suggest a potential mechanism for the establishment of crossmodal integration.},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T0G-4RC2S4D-2-1&_cdi=4862&_user=29041&_orig=search&_coverDate=02%2F06%2F2008&_sk=995689996&view=c&wchp=dGLzVlz-zSkWb&md5=dacc80ebc92561908fa87af679919019&ie=/sdarticle.pdf},
state = {published},
DOI = {10.1016/j.neulet.2007.11.069},
author = {Takagaki K, Zhang C, Wu JY and Lippert MT{mlippert}}
}

@Article{ 4649,
title = {Improvement of visual contrast detection by a simultaneous sound},
journal = {Brain Research},
year = {2007},
month = {10},
volume = {1173},
pages = {102-109},
abstract = {Combining input from multiple senses is essential for successfully mastering many real world situations. While several studies demonstrate that the presentation of a simultaneous sound can enhance visual detection performance or increase the perceived luminance of a dim light, the origin of these effect remains disputed. The suggestions range from early multisensory integration to changes in response bias and cognitive influences - implying that these effects could either result from relatively low-level, hard-wired connections of early sensory areas or from associations formed higher in the processing stream. To address this question, we quantified the effect of a simultaneous sound in various contrast detection tasks. A completely redundant sound did not alter detection rates, but only speeded reaction times. An informative sound, which reduced the uncertainty about the timing of the visual display, significantly improved detection rates, which manifested as a significant shift of the contrast detection cur
ve. Surprisingly, this improvement occurred only in a paradigm were there was a consistent timing relation between sound and target and disappeared when subjects were not aware of the fact that the sound offered information about the visual stimulus. Altogether our findings suggest that cross-modal influences in such simple detection tasks are not exclusively mediated by had-wired sensory integration but rather point to a prominent role for cognitive and attention-like effects.},
file_url = {/fileadmin/user_upload/files/publications/Lippert_BrainRes_07_4649[0].pdf},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6SYR-4PCPFM5-6-1&_cdi=4841&_user=29041&_orig=search&_coverDate=10%2F10%2F2007&_sk=988269999&view=c&wchp=dGLbVzb-zSkWb&md5=8920},
state = {published},
DOI = {10.1016/j.brainres.2007.07.050},
author = {Lippert M{mlippert}{Department Physiology of Cognitive Processes}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}}
}

@Article{ 5358,
title = {Methods for voltage-sensitive dye imaging of rat cortical activity with high signal-to-noise ratio},
journal = {Journal of Neurophysiology},
year = {2007},
month = {7},
volume = {98},
number = {1},
pages = {502-512},
abstract = {We describe methods to achieve high sensitivity in voltage-sensitive dye (VSD) imaging from rat barrel and visual cortices in vivo with the use of a blue dye RH1691 and a high dynamic range imaging device (photodiode array). With an improved staining protocol and an off-line procedure to remove pulsation artifact, the sensitivity of VSD recording is comparable with that of local field potential recording from the same location. With this sensitivity, one can record from approximately 500 individual detectors, each covering an area of cortical tissue 160 microm in diameter (total imaging field approximately 4 mm in diameter) and a temporal resolution of 1,600 frames/s, without multiple-trial averaging. We can record 80-100 trials of intermittent 10-s trials from each imaging field before the VSD signal reduces to one half of its initial amplitude because of bleaching and wash-out. Taken together, the methods described in this report provide a useful tool for visualizing evoked and spontaneous waves from rodent
cortex.},
web_url = {http://jn.physiology.org/cgi/content/full/98/1/502},
state = {published},
DOI = {doi:10.1152/jn.01169.2006},
author = {Lippert MT{mlippert}, Takagaki K, Xu W, Huang X and Wu J-Y}
}

@Article{ 3562,
title = {Mechanisms for allocating auditory attention: an auditory saliency map},
journal = {Current Biology},
year = {2005},
month = {11},
volume = {15},
number = {21},
pages = {1943-1947},
abstract = {Our nervous system is confronted with a barrage of sensory stimuli, but neural resources are limited and not all stimuli can be processed to the same extent. Mechanisms exist to bias attention towards the particularly salient events thereby providing a weighted representation of our environment [1]. Our understanding of these mechanisms is still limited, but theoretical models can replicate such a weighting of sensory inputs and provide a basis for understanding the underlying principles [2, 3]. Here we describe such a model for the auditory system – an auditory saliency map. We experimentally validate the model on natural acoustical scenarios demonstrating that it reproduces human judgments of auditory saliency and predicts the detectability of salient sounds embedded in noisy backgrounds. In addition, it also predicts the natural orienting behavior of naïve macaque monkeys to the same salient stimuli. The structure of the suggested model is identical to that
of
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essf
ully
use
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sual saliency maps. Hence we conclude that saliency is determined either by implementing similar mechanisms in different unisensory pathways, or by the same mechanism in multisensory areas. In any case, our results demonstrate that different primate sensory systems rely on common principles for extracting relevant sensory events.},
file_url = {/fileadmin/user_upload/files/publications/Kayser_CurrentBiology_05_3562[0].pdf},
web_url = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6VRT-4HH8DGG-X-B&_cdi=6243&_user=29041&_orig=search&_coverDate=11%2F08%2F2005&_sk=999849978&view=c&wchp=dGLbVtb-zSkzS&md5=803d2148009bc032de6a8539f2cc79b5&ie=},
state = {published},
DOI = {10.1016/j.cub.2005.09.040},
author = {Kayser C{kayser}{Department Physiology of Cognitive Processes}, Petkov CI{chrisp}, Lippert M{mlippert}{Department Physiology of Cognitive Processes} and Logothetis NK{nikos}{Department Physiology of Cognitive Processes}}
}

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

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