Direct structural connections between auditory and visual motion-selective regions in humans

Center for Mind/Brain Sciences, University of Trento, Rovereto, 38068, Italy, and 3Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 01129 In humans, the occipital middle-temporal region (hMT1/V5) specializes in the processing of visual motion, while the planum temporale (hPT) specializes in auditory motion processing. It has been hypothesized that these regions might communicate directly to achieve fast and optimal exchange of multisensory motion information. Here we investigated, for the first time in humans (male and female), the presence of direct white matter connections between visual and auditory motion-selective regions using a combined fMRI and diffusion MRI approach. We found evidence supporting the potential existence of direct white matter connections between individually and functionally defined hMT1/V5 and hPT. We show that projections between hMT1/V5 and hPT do not overlap with large white matter bundles, such as the inferior longitudinal fasciculus and the inferior frontal occipital fasciculus. Moreover, we did not find evidence suggesting the presence of projections between the fusiform face area and hPT, supporting the functional specificity of hMT1/V5-hPT connections. Finally, the potential presence of hMT1/V5-hPT connections was corroborated in a large sample of participants (n = 114) from the human connectome project. Together, this study provides a first indication for potential direct occipitotemporal projections between hMT1/V5 and hPT, which may support the exchange of motion information between functionally specialized auditory and visual regions.