We have shown in previous research that motion processing through echolocation activates temporal-occipital cortex in blind echolocation experts. Here we investigated how neural substrates of echo-motion are related to neural substrates of auditory source-motion and visual motion. Three blind echolocation experts and twelve sighted echolocation novices underwent fMRI scanning while they listened to binaural recordings of moving or stationary echolocation or auditory source sounds located either in left or right space. Sighted participants brain activity was also measured while they viewed moving or stationary visual stimuli. For each of the three modalities separately (echo, source, vision) we then identified motion sensitive areas in temporal-occipital cortex and in the planum temporale (PT). We then used a region of interest (ROI) analysis to investigate cross-modal responses, as well as laterality effects. In both sighted novices and blind experts we found that temporal-occipital source-motion ROIs did not respond to echo-motion and echo-motion ROIs did not respond to source motion. This double-dissociation was absent in PT ROIs. Furthermore, temporal-occipital echo-motion ROIs in blind, but not sighted, participants showed evidence for contralateral motion preference. Temporal-occipital source-motion ROIs did not show evidence for contralateral preference in either blind or sighted participants. Our data suggest a functional segregation of processing of auditory source-motion and echo-motion in human temporal-occipital cortex. Furthermore, the data suggest that the echo-motion response in blind experts may represent a reorganization rather than exaggeration of response observed in sighted novices. There is the possibility that this reorganization involves the recruitment of 'visual' cortical areas.
- Copyright © 2013, Journal of Neurophysiology