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Kevin C Chan, Matthew C. Murphy, Christopher Fisher, Seong-Gi Kim, Joel S Schuman, Amy C. Nau; Relationship between visual brain connectivity and duration of blindness depends on onset of visual deprivation. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4079.
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© ARVO (1962-2015); The Authors (2016-present)
Visual deprivation is known to induce plasticity of the visual system, which can be observed through alterations in functional brain connectivity (FC) by functional MRI (fMRI). How these FC changes accrue over time in congenital and acquired blindness remains uncertain. This work aimed to model the effects of prior visual experience on visual FC in blind subjects.
Seven congenitally blind and 11 age-matched acquired blind subjects underwent 8 minutes of fMRI at rest using a 3 Tesla scanner. A visual FC map was constructed for each subject by computing the average correlation coefficient between the extrastriate visual cortex and each voxel in the brain. We then examined the effects of visual experience by fitting these FC maps with a linear model with predictors including duration of blindness, a dummy variable for congenital blindness, and the interaction of these two effects. T score maps of these effects were thresholded at a family-wise error corrected p<0.01.
From the maps of voxel-wise statistical testing (Fig. 1), more than 6 times as many voxels in the brain show a significant group by duration interaction effect (row 4) compared to a simple correlation with duration of blindness (row 2), indicating that the relationship between visual FC and duration of blindness is significantly different between congenital and acquired blindness. In general, the sign of the correlation between FC and duration of blindness in congenital subjects is opposite to that in acquired subjects. Similar findings are observed when using striate cortex instead of extrastriate cortex as the seed region of interest (data not shown).
This work represents an early step toward understanding plasticity in the visual system and how it depends upon prior visual experience. These results suggest that alterations in FC due to visual deprivation progress over time but in opposite directions between congenital and acquired blindness. Our findings indicate that longitudinal measures of FC and not only FC alone may be essential for characterizing the state of the visual system.
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