A critical review of mental imagery defects.

A critical, clinical review of single-case reports and group studies on visual mental imagery deficits is offered. Neuropsychological findings demonstrate that mental imagery relies upon dissociable processes which are localized in left-hemisphere posterior areas. Imagery defects thus may often be associated with visual recognition and naming impairments. On the other hand, the right hemisphere seems to play an analogous role in imagery and perception. Current theoretical models of imagery do not appear fully capable of accounting for available clinical data.