Knowledge of visual attributes in the right hemisphere.

Neurobiological theories of knowledge processing are biased toward the language-dominant (usually the left) hemisphere. Does the right hemisphere critically contribute to knowledge processing? J.A. is a left-hemisphere language-dominant individual who suffered a lesion confined to the right mid- and anterior fusiform gyrus. Although her language abilities are intact, she showed a partial loss of knowledge of the visual attributes of biological and nonbiological entities. This was observed regardless of the task performed: object discrimination, oral feature generation, forced-choice naming-to-definition or free-hand drawing. Functional-associative and nonvisual sensory attributes were spared. The same region that was lesioned in J.A. was activated in a functional magnetic resonance imaging study in 27 volunteers who retrieved semantic associations between concepts, but only if the concepts were represented as pictures and not as words. Therefore, right fusiform gyrus critically contributes to the conscious recollection of visual attributes of familiar entities.