The goal of the proposed pilot research is to improve our understanding of the functional neural basis of age-related changes and constancies in memory performance in a group of 50 healthy older subjects (age range 55- 85) who are well characterized in terms of medical history, neurological and psychiatric health, and neuropsychological status. The performance of these subjects on tests of memory will be compared to that of 50 younger subjects (age 17-25) in a cross-sectional pilot study intended to establish the utility of a longitudinal memory systems analysis of the effect of aging upon new learning capacities. The tests are selected to be sensitive to three hypothesized memory systems, a memory system being a particular neural network thought to mediate a specific form of learning. We hypothesize that older subjects (relative to younger subjects) will (a) perform poorly on tests of verbal and pictorial recall, memory for temporal order, and category exemplar production due to selective vulnerability of a putative fronto-striatal memory system; (b) perform as well as younger subjects on a test of picture-naming speed due to the sparing of a putative occipital memory system that is also though to be spared in early AD; and (c) show a modest reduction that correlates with age in the older group on a word-completion test thought to reflect the operation of a temporo- parietal memory system that is especially vulnerable to the early stages of AD. The newly obtained evidence will guide the development of a preliminary theory relating the typical sequence of neural-system alterations in aging to the pattern of preserved and impaired learning capacities demonstrated by older people. The potential value of such a memory systems analysis of age-related changes in new learning capacities is that it may provide a useful way to discover patterns of continuity and discontinuity between age-related and AD-related changes in memory performance. Because it is motivated by what is known about structural and functional changes that occur in the aging and in the AD brain, memory systems analysis ought to be useful in the effort to find interventions that reduce memory loss in healthy and in pathological aging.
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