Large-scale imbalance in the brain network coding for auditory motion information induced by early visual deprivation

The extrastriate occipital structure hMT+/V5 is classically considered to implement motion processing from visual inputs only. However, recent studies have suggested the presence of motion-related information from non-visual modalities in this region in blind and sighted individuals. In the present study, we aim to characterize if auditory motion information is represented in hMT+/V5 in both the congenitally blind and sighted individuals using multivariate pattern analysis (MVPA). Brain activity was characterized using functional magnetic resonance imaging while participants listened to pink noise auditory stimuli depicting in-depth motion, horizontal motion, and static sounds. A single multi-class linear support vector machine (SVM) classifier was trained and tested for each subject separately to classify between the response patterns of three auditory conditions. Our results suggest the presence of auditory motion-related information in hMT+/V5 in both groups, but to a significantly higher extend in blind individuals. A whole brain searchlight approach revealed that occipito-temporal region (overlapping with the univariate definition of hMT+/V5) was the only brain region containing enhanced auditory motion information in the blind when compared to the sighted group. Importantly, and in striking contrast with what was observed in hMT+/V5, we observed that more auditory motion information is represented in the auditory cortex (including the planum temporale) of sighted individuals compared to the congenitally blind. These results suggest that early visual deprivation triggers a large-scale imbalance between separate audio-visual brain regions dedicated to the processing of motion information