NEURAL PLASTICITY ASSOCIATED WITH BRAILLE LEARNING

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DESCRIPTION: This study addresses the extent to which unused cortical areas normally subserving one sense can be taken over by another sense when a new task is presented. Previously, we have demonstrated that blind Braille readers use the 'visual' cortex during tactile Braille reading. This suggests that after visual input deafferentation, striatal neurons are capable of responding to input from other senses (touch). Now we want to investigate whether this phenomenon is due to unmasking of latent connections by studying the effects of intensive tactile Braille training on striatal activity in blindfolded sighted subjects. Four groups of sighted subjects will either be blindfolded or not for the duration of the study (7 days) and either undergo intensive tactile training or not. Neurophysiologic and neuroimaging techniques will be used to evaluate sensorimotor and visual cortical activity at the beginning and the end of the 7 day study period. We hypothesize that: (1) regardless of visual function, learning tactile Braille will be associated with an enlargement of the sensory representation of the pad of the reading finger. Functional MRI (fMRI) and somatosensory evoked potentials (SEP) will be used to test this hypothesis; (2) visually deprived subjects will learn tactile Braille faster than non-visually deprived sighted subjects. Learning curves for Braille character recognition will be generated by daily testing of all subjects with a specially designed Braille stimulator; and (3) learning Braille is visually deprived subjects will be associated with activation of occipital visual cortex due to unmasking of existing connections. In non-visually deprived subjects this process will not take place. SEP, fMRI, neurophthalmologic and neuropsychologic evaluations will be used to study the function of striatal cortex at the beginning and end of the 7 day study period. The results will enhance our understanding about the capabilities of the adult human brain to reorganize following an injury and provide important information for the design of strategies to optimize adjustment to loss of sight in particular, and recovery of function following neural injury in general.