[Implicit memory in patients with Alzheimer disease: a concise review]

Experimental psychologists have made a distinction between explicit and implicit memory tasks. In contrast to explicit tasks implicit ones do not refer to conscious recollection of a previous learning episode. Implicit memory is revealed by a change in task performance which can be attributed to previous learning. Amnesic patients, by definition, perform poorly on explicit memory tasks, but exhibit normal performance on certain implicit tasks. In recent years, investigators have studied the implicit memory capabilities of patients with Alzheimer's disease. The present article aims to give an overview of the performance of Alzheimer patients on four tasks of implicit memory. Compared with normal elderly persons, patients with Alzheimer's disease seem to demonstrate impaired performance on conceptual, but not on perceptual implicit memory tasks. This dissociation could yield important information about the neurological systems subserving implicit memory processes. Some suggestions for future research into implicit memory in Alzheimer patients are given.