fMRI Studies of the Visual System in Deaf Individuals

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DESCRIPTION (provided by applicant): Although plasticity is a fundamental property of the human nervous system, the specificity with which different cortical regions are modifiable, and under what circumstances, is not yet known. Congenital deafness and early acquisition of American Sign Language (ASL) provide a unique opportunity to explore experience-dependent changes due to altered sensory experience. Changes in the functional anatomy of the dorsal visual processing pathway have been reported for such populations for motion processing, but studies of the ventral pathway are lacking. Deaf signers rely predominantly on vision for communication, and are disproportionately dependent on facial cues compared to hearing individuals. Lacking auditory cues, the deaf must garner both affective and linguistic information from others' faces and attend to linguistic facial expressions unique to ASL. Behavioral data indicate a face processing advantage for native deaf and hearing signers, compared to hearing non-signers, yet the neural locus of these effects is unknown. This study uses fMRI to investigate experience-dependent changes in dorsal and ventral visual pathway functions. Deaf signers, hearing signers, and hearing non-signers will be scanned while attending to spatial location or object identity using identical stimuli. The location task will determine if functional reorganization reported for motion processing generalizes to other dorsal pathway functions, and the object task, including both faces and a non-face object, will determine whether analogous reorganization occurs in the ventral pathway, and if it is specific to faces or generalizes to other object categories. Changes due to auditory deprivation and ASL acquisition may include plasticity of the spatial and object perception/ networks, and recruitment of auditory cortex for visual processing.