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Samantha I. Cunningham, James D. Weiland, Pinglei Bao, Bosco S. Tjan; Primary Visual Cortex Activation Responses to Tactile Stimulation in Late-Blind Individuals with Retinitis Pigmentosa. Journal of Vision 2012;12(9):1327. doi: https://doi.org/10.1167/12.9.1327.
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© ARVO (1962-2015); The Authors (2016-present)
Previous fMRI studies suggest that vision deprivation in humans causes the visual cortex to be modulated by the processing of tactile stimuli. This cross-modal activation, if correlated with vision loss, can be used to assess vision restoration progress following sight-recovery treatments. We measured the extent of cross-modal responses in the visual cortex of seven late-blind individuals with retinitis pigmentosa (RP), a genetic degenerative disease that results in gradual tunnel vision and blindness. RP and sighted control groups completed two tactile tasks: a roughness discrimination task using sandpaper discs and a symmetry discrimination task using raised-line shapes. For each subject, we quantified the extent of the tactile-evoked activation by the percentage of significantly activated voxels within V1, and the strength of the activation by the mean absolute modulation amplitude of the activated voxels. These quantities were evaluated as a function of visual-field loss. The strength of the BOLD signal response and percentage of activated voxels within V1 increased with increasing visual-field loss for the sandpaper task (p’s <0.05). RP subjects with the greatest degree of vision loss exhibited the strongest visual cortex activation with sandpaper stimulation over the largest cortical extent in V1. For the shapes task, which evoked a weaker response, the order of the means were consistent with that for the sandpaper task, but the differences did not reach significance (p’s > 0.10). Comparison of BOLD responses among RP subjects during the sandpaper task revealed a localization of tactile-evoked activity to regions most affected by vision deprivation; greater peripheral vision loss lead to stronger activation in peripheral V1. In summary, V1 responses to tactile stimulation seem to be task dependent. For the task that evoked a strong response, a strong correlation was found between degree and location of visual-field loss with the degree and location of tactile-evoked activation in V1.
Meeting abstract presented at VSS 2012
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