Some effects of disconnecting the cerebral hemispheres.

To start by looking back a little, recall that even a small brain lesion, if critically located in the left or language hemisphere, may selectively destroy a person's ability to read, while at the same time sparing speech and the ability to converse. The printed page continues to be seen, but the words have lost their meaning. This condition typically follows from focal damage to the angular gyrus in the left hemisphere. It also results from lesions interruptingt he neural input to this left angular gyrus from the visual or calcarine cortical areas (1, 2). It is natural to conclude in such cases that the left hemisphere is responsible for reading while the undamaged right hemisphere, in contrast, must be "wordblind" or incapable of seeing meaning in the printed word.

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