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Abstract

Merging information from different senses is essential for successfully interacting with real world situations. ndeed, sensory integration can reduce perceptual ambiguity, speed reactions or change the qualitative sensory experience. It is widely held that this process of integration occurs at later processing stages and mostly in higher association cortices. However, many recent studies suggest that sensory convergence can already occur in primary sensory areas. Combining functional imaging and electrophysiological studies we use the auditory system as a model to study how early during auditory processing influences of other modalities can occur. Especially, combining different techniques allows us to bridge a gap between human imaging literature and anatomical and physiological knowledge from animals. Our results demonstrate that auditory processing is well susceptible to modulation by visual and somatosensory stimulation, suggesting that a large part of the brain has to be regarded as ‘multisensory’. In addition, combining evidence from functional and behavioral experiments suggests that there might be profound asymmetries between the different senses with regard to cross-modal interactions. These results suggest that we have to abandon the classical text-book view of separated unisensory processing streams that merge only at the last stage of sensory processing. Instead, our brain tries to merge the complex information provided by the different senses already early on to provide us with a unified and coherent percept of our environment.