Neural Plasticity Associated with Braille Learning

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DESCRIPTION (provided by applicant): In our initial funding cycle we compared sighted subjects who were visually deprived for five days with non-visually deprived sighted subjects as they learned tactile Braille character recognition. Serial psychophysics and functional magnetic resonance imaging (fMRI) studies revealed that (1) visually deprived subjects learn tactile Braille reading significantly faster than non-visually deprived sighted subjects; and that (2) learning Braille in visually deprived subjects is associated with activation of occipital visual cortex. Furthermore, we found that auditory information processing can also be associated with activation of the occipital cortex in visually deprived subjects. These results are reminiscent of the findings in early blind subjects in whom the occipital cortex is recruited for tactile Braille reading and auditory processing. However, the rapid time course of our findings in the blindfolded sighted subjects is remarkable and raises questions about its functional significance and underlying mechanisms. The present proposal is designed to address these issues. Visually deprived normal subjects with or without intensity tactile stimulation and Braille teaching will be compared with sighed controls. Comparisons will be made with-in subjects across time and across subjects comparing the different study groups. All subjects will undergo three experiments repeated at various times during the study. First, we will use fMRI of a spatial and a non-spatial visual, tactile and auditory task to reveal information about which specific brain areas are activated in association with a given perceptual operation and sensory modality. We hypothesize that (1) the same occipital areas recruited during visual spatial tasks in sighted subjects will also be recruited, in the visually-deprived state, during auditory and tactile spatial tasks; and (2) the same relation will be true for the non-spatial tasks, but less involvement of the occipital cortex will be noted. Second, transcranial magnetic stimulation (TMS) will be used to provide information about whether and when the contribution of a given cortical region is critical for task performance. We hypothesize that (1) in blindfolded subjects performance in spatial tasks (both tactile or auditory versions) will be disrupted by TMS of the occipital cortex easier than performance in non-spatial tasks; and that (2) the timing of TMS of the occipital cortex for disruption of spatial tactile and auditory tasks will be different. Finally, transcranial stimulation during fMRI will be used to study changes in functional connectivity of the visual cortex that may arise during the visual-deprivation and account for the activation of the visual cortex during tactile and auditory processing. The results will further characterize cross modal plasticity during visual deprivation, and illustrate fundamental aspects of the mechanisms involved in determining cortical functional specificity and those engaged in perceptual representation of the world.