Language and memory functions after long recovery periods in left-hemispherectomized subjects.

Two subjects who had infantile brain damage and left hemispherectomies at the ages of 17 and 18 yr are assessed after 28 and 16 yr recovery periods. Deficits on the comprehension of passive-negative sentences disappeared when the subjects read rather than heard the sentences, and performances were normal on the Token and Reporter's Tests, and tests of verbal memory. These results suggest that if damage to the left hemisphere occurs early in life and there is a long recovery period, the right hemisphere can mediate verbal memory and the more subtle aspects of language. This provides support for the hypothesis that the two hemispheres are equipotential for language and verbal memory.