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Meeting Abstract

Multisensory integration in early auditory areas


Kayser,  C
Max Planck Institute for Biological Cybernetics, Max Planck Society;
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Kayser, C. (2007). Multisensory integration in early auditory areas. Neural Plasticity, 2007: 23250, 29.

Cite as: http://hdl.handle.net/21.11116/0000-0002-D8F9-2
An increasing body of literature from functional imaging, electrophysiology and anatomy provides compelling evidence that merging of sensory information not only occurs in higher association areas, but also in lower sensory regions. To investigate early cross-modal interactions in detail, we use the macaque auditory cortex as model and employ a combination of high-resolution imaging (fMRI) and electrophysiological recordings. In the imaging data, few voxels respond to non-auditory stimulation alone, but many show cross-modal interactions in the form of supra-linear enhancement; i.e., the multimodal response exceeds the linear superposition of the unisensory responses. This effect is reliably found at the caudal end and along the lateral side of the secondary auditory cortex, and can be localized to the medial and caudal belt and caudal parabelt regions. This interaction obeys the classical rules for sensory integration: it occurs only for temporally coincident stimuli and follows the principle of inverse effectiveness (integration is stronger for less effective stimuli). Complementary electrophysiological recordings demonstrate that the imaging results are nicely paralleled by similar findings in the low frequency local field potentials. Individual neurons, however, often show the opposite effect and exhibit a decreased response when a visual stimulus is presented simultaneously with a sound. This audio-visual depression occurs with a time lag of about 40-80 ms, and for a wide range of simplistic and naturalistic stimuli. Altogether, our results clearly support the notion that early sensory cortices are susceptible to modulation by different senses. However, for individual neurons these effects are subtle and can be better detected at the level of population responses. Future studies need to resolve where exactly this cross-modal input originates and how it aids the auditory system to segregate our complex acoustical environment.