Trends in Cognitive Sciences
Cortical plasticity associated with Braille learning
Section snippets
Enlarged somatosensory representation of braille-reading fingers
Evidence from both animal and human models suggests that somatosensory representation of a body part can be selectively remodeled by new tactile experiences, and that repeated use or stimulation of that portion of the body can lead to an enlarged cortical representation. The work of Merzenich and colleagues7, 8, 9, 10, 11using animal models suggests that these changes in cortical representation might underlie changes in perception. Recanzone et al.[12]found that the topographical and temporal
Occipital cortex activation in early-blind braille readers: true cross-modal plasticity
What becomes of those occipital portions of a blind individual's cortex that would otherwise have subserved visual processing? Can they be re-allocated to subserve new functions, or even different sensory modalities? The answer to the latter question, at least in the case of `early-blind' Braille readers (subjects born blind or that had become blind before the age of 7), appears to be yes. Using positron emission tomography (PET) as a measure of cortical activation during tactile discrimination
Using TMS to track the flow of spatial information in early-blind braille readers
Having demonstrated that the visual cortex of early-blind Braille readers is activated by tactile discrimination tasks, questions such as how and when tactile information reaches the visual cortex may be pursued. TMS is a useful method with which to approach these questions. Appropriately delivered in time and space, TMS can transiently disrupt the arrival of the thalamo-cortical volley of afferent signals into the primary sensory cortex and thereby interfere with detection of peripheral
Conclusions
Blind subjects demonstrate remarkable neuroplastic changes in response to the adjustment to blindness and the acquisition of Braille-reading skill. This reorganization appears to involve two distinct processes. First, there is enlargement of the somatosensory representation of the Braille reading finger, which probably reflects both rapid unmasking of existing cortical connections and slower, more enduring structural changes. Secondly, at least in early-blind subjects, the occipital, `visual'
Acknowledgements
Supported in part by grants from the Milton Fund, the Stanley Vada-NAMI Foundation, the Spanish Research Council (DGCYT), the General Clinical Research Center at BIDMC (NIH RR 01032) and the National Eye Institute (RO1 EY12091).
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