A case study of mental imagery deficit.

We describe a patient with a deficit in imagery ability, following a left posterior cerebral artery infarction and possible anoxic episode. This deficit was inferred from the patient's performance on several tasks, including one in which normal adults are known to rely on imagery and two that tested imagery nonverbally, allowing us to examine the possibility of a language-imagery disconnection. In addition, we queried the patient on some cognitive capacities related to visual imagery: dreaming, geographical knowledge, and introspection regarding visual and auditory imagery. Hypotheses concerning the critical lesion site and underlying cognitive mechanism of image generation deficits are discussed in relation to this and other recent cases of impaired imagery ability with intact recognition ability, and the relevance of this deficit to the "imagery debate" is discussed.