Event-related brain potentials (ERPs) and behavioral indices will be recorded from normal young and elderly subjects. Converging evidence from ERP and behavioral reports, as well as from studies of amnestics, suggest that performance on tasks which do (explicit memory) and do not (implicit memory) require the conscious recollection of items stored in memory may reflect cognitively distinct systems and, further, that their underlying brain mechanisms may also be distinct. Recent evidence suggests that the elderly may show deficits on both types of memory test. Moreover, there is evidence suggesting that the elderly show changes in frontal lobe function that may partially explain their memory problems. This proposal is designed to begin to investigate the conjunction among these various sources of evidence using the ERP's exquisite temporal resolution, and recent techniques for modelling the likely brain sources of ERP components during tests of implicit and explicit retention, in an attempt to better understand age-related differences in memory function. Each of the memory experiments includes a study phase, with subsequent implicit and explicit memory testing of those items presented during the study series. In this fashion, ERPs and behavior can be compared among age groups, between implicit and explicit tests, and for the interaction of age and type of memory test. For each memory experiment, and for the replication of our novelty study, ERPs will be recorded from 29 scalp leads, thus allowing us to model their putative brain generators using Scherg's source localization technique. This will enable us to determine if those ERP component sources differ for implicit and explicit tests and for each type of test between the young and the elderly. Such data could strengthen (or weaken) the position that implicit and explicit performance are subserved by different physiological systems as well as aid in better modelling the brain changes correlated with memory deficits that occur in normal aging. These data will have application to brain models of normal aging as well as for deviant aging, e.g., Alzheimer's disease, in which memory dysfunction is a consequence of deterioration in brain function.
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