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------------------------------------------------------------------------ New Findings Explain Why Blind People Have Superior Tactile Abilities ------------------------------------------------------------------------ WESTPORT, Sep 17 (Reuters) - In people who are blind from birth or from early childhood, the area of the brain that usually processes visual information is used instead to process sensory input from touch. This finding, which helps to explain why blind people often have superior tactile abilities, is reported in the September 11 issue of Nature. Dr. Leonardo G. Cohen of the National Institute of Neurological Disorders and Stroke in Bethesda, Maryland, with colleagues in Argentina, Boston, and Japan, explains that while it was known that tactile discrimination tasks, such as Braille reading, activate the visual cortex in blind individuals, it has not been clear whether "...the visual cortex can process somatosensory information in a functionally relevant way." Dr. Cohen and his team used transcranial magnetic stimulation to interfere temporarily with the function of various cortical areas of blind subjects as they attempted to identify Braille or embossed Roman letters. The investigators also tested normal-sighted control subjects as they attempted to identify only the Roman letters. "Transient stimulation of the occipital (visual) cortex induced errors in both tasks and distorted the tactile perceptions of blind subjects," the researchers report. "In contrast, occipital stimulation had no effect on tactile performance in normal-sighted subjects, whereas similar stimulation is known to disrupt their visual performance." "These results show that cross-modal plasticity...in humans may be involved in functional compensation," Dr. Cohen and his colleagues conclude. Nature 1997;389:180-183. Copyright 1997 Reuters Limited. <http://www.reutershealth.com/news/docs/199709/19970917scc.html> ------------------------------------------------------------------------ [log in to unmask]