Direct Structural Connections between Auditory and Visual Motion-Selective Regions in Humans.

In humans, the occipital middle-temporal region (hMT+/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 hMT+/V5 and hPT. We show that projections between hMT+/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 hMT+/V5-hPT connections. Finally, the potential presence of hMT+/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 hMT+/V5 and hPT, which may support the exchange of motion information between functionally specialized auditory and visual regions.SIGNIFICANCE STATEMENT Perceiving and integrating moving signal across the senses is arguably one of the most important perceptual skills for the survival of living organisms. In order to create a unified representation of movement, the brain must therefore integrate motion information from separate senses. Our study provides support for the potential existence of direct connections between motion-selective regions in the occipital/visual (hMT+/V5) and temporal/auditory (hPT) cortices in humans. This connection could represent the structural scaffolding for the rapid and optimal exchange and integration of multisensory motion information. These findings suggest the existence of computationally specific pathways that allow information flow between areas that share a similar computational goal.