DESCRIPTION: Adults with Down syndrome (DS) experience changes in functioning associated with normal aging precociously, and they are at higher risk for developing Alzheimer's disease than their peers with other forms of mental retardation (MR). The first aim of the proposed project is to characterize specific changes in memory and cognitive processing that occur during normal aging and to identify individual differences in vulnerability to early onset of age-associated changes in adults with DS. This project will focus on the study of working and episodic memory, two systems known to be sensitive to aging processes. Each of the components of a model of working memory (central executive function, visuospatial sketchpad, phonlogical loop; Baddeley, 1986) will be tested with multiple converging measures. The second aim is to distinguish the patterns of change in performance on tests of memory and cognition that are associated with normal aging from changes associated with early dementia of the Alzheimer type. The third aim is to describe the natural history of dementia in adults with MR. Individual performance on tests of memory and cognition will be related to mental status and caregiver informant-based scales of adaptive behavior and dementia. Because the test battery spans a broad range of cognitive domains and difficulty, it will be possible to describe the course of decline from early onset through to advanced stages of dementia. By the end of the proposed study those tests that are most sensitive to early declines in functioning will have been identified and their utility as clinical instruments verified with longitudinal measures. By delineating the changes in specific memory and cognitive processes related to individual differences in normal and abnormal aging in adults with DS, this work will contribute to understanding vulnerability to age-related changes, in general.