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Abstract:
Previous studies suggest that congenital deafness alters the
functional organization of the dorsal stream of the visual system.
Using fMRI, we assessed whether early auditory deprivation changes
the recruitment of motion processing areas. In addition,we
hypothesized that these changes will be most marked when visual
attention is required. Motion processing was compared between
congenitally deaf (native signers/born to a deaf parent) and
hearing individuals as visual attention was manipulated. Methods:
Echo Planar Images were collected at 1.5T (20 slices, TR=4sec,
3.5x3.5x5.5mm). Ten subjects were run in each group. Subjects
fixated centrally and viewed an alternation of radial flow fields
(converging and diverging) and static dots. While the first run
required only passive viewing, visual attention was manipulated in
all other runs by asking subjects to detect velocity and/or
luminance changes. Data were analyzed with SPM96.
Results: Deaf individuals showed a greater number of voxels
activated and a larger percent signal change than hearing subjects
in MT-MST when attention was manipulated. Thus, congenital deafness
changes the cortical organization of motion processing especially
when attention is required. Interestingly, the recruitment of the
Intraparietal sulcus was also significantly larger in deaf than in
hearing subjects. This result suggests that early auditory
deprivation may also alter the cortical organization of visual
attention. Indeed, the parietal cortex is known to be important for
attentional processing.
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