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Alexandra Levine, Shradha Billawa, Laura Bridge, Sally Clausen, Mark Hymers, Heidi Baseler; FMRI correlates of visual motion processing in hearing and deaf adults. Journal of Vision 2014;14(10):297. doi: https://doi.org/10.1167/14.10.297.
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Lack of auditory stimulation experienced by the congenitally, profoundly deaf can lead to greater visual sensitivity, particularly to peripheral visual motion (Buckley et al. 2001). Previous research attributes this advantage in part to greater recruitment of area V5 in deaf than hearing individuals (Bavelier et al. 2001). However, recent data have shown that structural differences as early as the retina correlate with peripheral motion sensitivity in deaf and hearing adults (Codina et al. 2011). The current study evaluated neural responses in early visual cortical areas and investigated the relationship between cortical activation and visual performance differences in deaf and hearing adults. Participants included fourteen hearing and four congenitally, profoundly deaf adults without visual deficits. Motion direction discrimination thresholds were measured in each individual using an optic flow stimulus restricted to the central (0-5˚) or peripheral (40-72˚) visual field. FMRI responses were measured from each participant while viewing retinotopic mapping and optic flow motion stimuli. Peripheral stimuli extended out to +/-72˚ to include the far peripheral visual field, where visual sensitivity differences are greatest in the deaf. Activity within visual areas V1 and V5 was measured and correlated with psychophysical thresholds for each individual. V1 response magnitude in the far-peripheral representation was greater in deaf than hearing participants. Peripheral motion direction discrimination thresholds in all participants were significantly correlated with V5, but not V1 activation. V5 activation correlated with behavioural motion sensitivity in optic flow tasks in all participants, supporting this area's role in motion processing. In addition, deaf participants exhibited greater activation in far-peripheral representations in V1, advocating early visual pathway changes in response to hearing loss. Motion sensitivity did not correlate with V1 responses, however, suggesting that changes in early visual pathways may not mediate improved sensitivity for all types of peripheral motion tasks.
Meeting abstract presented at VSS 2014
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