FMRI ANALYSIS OF IMPLICIT MEMORY IN NORMAL AGING

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The goal of this proposal is to test a novel theory about the psychological and neural bases of age-related decline in repetition priming, a form of implicit memory. Recent reviews note a host of apparently contradictory findings concerning whether all or some forms of priming are preserved in normal aging. Traditional neuropsychological frameworks, such as the explicit/implicit or the perceptual/conceptual distinctions, appear unable to clarify these contradictions. Many of these findings may be accommodated by a theory that proposes that (1) the frontal-lobes make critical contributions to production, but not identification, forms of priming, and (2) frontal-lobe dysfunction is variable in normal aging. Normal old and Alzheimer's disease (AD) participants will be sampled from a single population and optimally and identically characterized along neurological and neuropsychological dimensions. They will be compared to a sample of young participants in a series of behavioral and functional magnetic resonance imaging (fMRI) studies that test the following specific hypotheses: 1) production forms of priming are reduced in old participants without clinical AD and further reduced in old participants with clinical AD, whereas identification forms of priming are not reduced in old participants with or without AD; 2) in old participants without clinical AD, production forms of priming are related to performance on cognitive tests that are known to be mediated by the frontal-lobes; 3) in young participants, production forms of priming make greater demands on frontal-lobe regions, measured by fMRI, than do identification forms of priming; and 4) in old participants without clinical AD, production forms of priming are related to fMRI measures of frontal-lobe function.