It is, by now, axiomatic, that older adult subjects demonstrate deficits, relative to young adults, on episodic or explicit test of memory, such as~ free recall, cued recall, and recognition, tests which require the conscious access to previously experienced events. However, the causes of these episodic memory deficits remain largely unknown. This revised proposal's major aim, therefore, is to test the hypothesis that alterations in executive, or cognitive control processes presumably mediated by the prefrontal cortex, can explain at least some of the older adults'decline in memory function ERP, EEG, and behavioral data will be obtained from young (20-30), young/old (60-70) and old/old (71-85) adults during series of episodic memory tasks and independent assessments of executive processing. The recruitment of 2 older age groups will enable the determination of continuity and/or discontinuity in memory function and underlying neurophysiology during the older adult years. The first two experiments are aimed at determining whether the older adults'encoding difficulties are due to a deficit in semantic retrieval per Se, or to a deficient cognitive control mechanism that enables the selection of semantic attributes from competing alternatives. The third experiment assesses the effect of resource allocation on age-related changes in episodic encoding. The fourth experiment tests the hypothesis that the older aduIts'source memory deficiencies may be due to a decline in encoding and retrieving """"""""bound"""""""" information. The final memory task assesses the effect of inhibitory control on episodic memory performance and whether knowledge of source information can overcome the older adult's difficulty in inhibiting the retrieval of no longer relevant mnemonic information The independent executive tasks, which will be administered to all subjects, assess the older adults'working memory span, ability to task switch, and verbal and category fluency, all quintessential, prefrontally-based cognitive contrc mechanisms. ERPs will be recorded from 62 scalp sites to enable good spatial resolution for current source density, and EEG coherence analyses. The latter will enable a better understanding of the possible age-related alterations in the neural networks underpinning episodic memory performance. The data will be relevant to age-related changes ii cognitive control mechanisms, prefrontal functioning, and episodic memory, and their physiological underpinnings.
Showing the most recent 10 out of 16 publications
