Visuospatial and other "right-hemispheric" 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. Both have intact language and verbal memory abilities. However, on functions normally mediated predominantly by the right hemisphere, including nonverbal memory, higher cognitive visuospatial skills, and complex extrapersonal orientation ability, they are severely impaired. Simple visuospatial perceptual and orientation abilities, emotional expression, and face recognition, also "right-hemispheric" functions, are normal. It is postulated that the right hemisphere, if isolated in infancy, has the potential to take over most cognitive functions. The pattern of intact and impaired abilities shown by these subjects allows a hierarchy of functionally important abilities to be constructed. The functions mediated by the solitary right hemisphere are those most essential for independent survival, and functions that are not represented are those least required.