CONSCIOUSNESS OF PERCEPTION AFTER BRAIN-DAMAGE

Disturbances of visual perception after brain damage provide clues to understanding consciousness and the brain. In this article we review s ix visual disorders in which perception and consciousness are dissocia ted as a result of brain damage: blindsight, implicit shape perception in apperceptive visual agnosia, covert recognition of faces in prosop agnosia, unconscious perception in neglect and extinction, implicit re ading in pure alexia, and implicit object recognition in associative v isual agnosia. We consider these six disorders from the standpoint of three main schools of thought concerning consciousness and the brain, namely a localized system for consciousness, consciousness as a state of integration, and consciousness as a property of graded representati on. The findings suggest that these syndromes do not share a single me chanism and that it is conceivable that more than one explanation will be necessary both within and across syndromes. We conclude on the bas is of the current evidence that it is unlikely that any single brain s ystem is necessary for conscious awareness of perception that does not play a role in perception as well.