Structural and functional network-level reorganization in the coding of auditory motion directions and sound source locations in the absence of vision

Abstract

AbstractHow does blindness affect the brain network supporting spatial hearing? We used a combined functional and diffusion MRI approach to study the impact of early blindness on the brain networks typically coding for audio-visual motion and location. Whole-brain functional univariate analysis revealed preferential response to auditory motion in a dorsal network including the planum temporale (hPT) as well as the anterior portion of the middle temporal cortex (hMT+/V5) in both sighted and congenitally blind participants (male and female). Blind participants showed additional preferential response to auditory motion in the posterior region of hMT+/V5. Importantly, multivariate decoding analysis revealed the presence of motion direction information that was higher in hMT+/V5 and lower in hPT of blind relative to sighted people. Decoding sound source location showed a similar pattern of results even if the decoding accuracies were in general lower than those obtained from motion directions. Diffusion MRI revealed that the macrostructure (trajectory and connectivity index) of hMT+/V5 – hPT connectivity did not differ between groups, while the microstructure of the connections was altered in blind people. These results suggest that early visual deprivation triggers a network-level reorganization that enhances the recruitment of occipital areas in conjunction with a release in the computational workload of temporal regions typically dedicated to spatial hearing. This functional reorganization is accompanied by white-matter microstructural alterations in related occipital-temporal connections.