More than meets the eye Processing of visual and auditory information in the sensory cortex

We experience the world around us using all our senses. When we see a cup fall and break on the floor, the image of the cup breaking and the sound of breaking pottery is bound together into a single sensory experience. This integration happens automatically and seemingly without any effort on our part. However, multisensory integration is a complicated process and it is still largely unknown how brain cells (neurons) in the brain perform this operation. Sensory information is gathered by our senses and sent to specialized brain regions, such as the primary visual cortex. For a long time, it was believed that visual cortex only processes visual information and that multisensory information is performed by other, more specialized areas. Contrary to this belief, in a series of experiments we showed that activity in the visual cortex was modulated by sound. This integration of multiple senses in the visual cortex allowed weak multisensory stimuli to be detected with higher accuracy. Furthermore, we found a part of the visual cortex which was involved in the detection of audiovisual, but not purely visual, stimuli in the environment. Because this part of visual cortex is closely connected to brain areas that initiate an action, we think it is important for the transformation of multisensory information into a behavioral response. Taken together, the work in this thesis presents an important step in our understanding of how the visual cortex processes multisensory information.