Differential effects of aging and Alzheimer's disease on conceptual implicit and explicit memory

The effects of aging and Alzheimer's disease (AD) on conceptual explicit and implicit memory were examined. Three groups of participants-patients with AD; age-matched, older control participants; and younger control participants-made deep (semantic) or shallow (nonsemantic) judgments about low-dominant category exemplars. Explicit memory was measured by category-cued recall and implicit memory was measured by priming on a category-exemplar generation task. Younger participants had enhanced cued recall and priming following deep, relative to shallow, encoding; this indicated that both memory measures were conceptually driven. Aging reduced explicit, but not implicit, test performance, and it did not reduce conceptually driven processes for either test. In contrast, AD reduced explicit and implicit test performance, and it impaired conceptually driven memory processes for both tests.