Diffusion tensor imaging shows white matter tracts between human auditory and visual cortex.

Although it is known that sounds can affect visual perception, the neural correlates for crossmodal interactions are still disputed. Previous tracer studies in non-human primates revealed direct anatomical connections between auditory and visual brain areas. We examined the structural connectivity of the auditory cortex in normal humans by diffusion-weighted tensor magnetic resonance imaging and probabilistic tractography. Tracts were seeded in Heschl's region or the planum temporale. Fibres crossed hemispheres at the posterior corpus callosum. Ipsilateral fibres seeded in Heschl's region projected to the superior temporal sulcus, the supramarginal gyrus and intraparietal sulcus and the occipital cortex including the calcarine sulcus. Fibres seeded in the planum temporale terminated primarily in the superior temporal sulcus, the supramarginal gyrus, the central sulcus and adjacent regions. Our findings suggest the existence of direct white matter connections between auditory and visual cortex--in addition to subcortical, temporal and parietal connections.