A five-year research program is described which is aimed at clarifying the relationships among normal aging, executive (suppression, shifting of focus, consolidation) and non-executive (activation, storage, decay) working memory (WM) operations, and language comprehension. It has been suggested that along with age comes a reduced WM capacity which is manifest not only in a greater tendency to forget but also in an increased difficulty making sense of structurally complex sentences (comprehension), in switching from one idea or action to another quickly (attentional switching), and in ignoring and/or suppressing that which is irrelevant (inhibition). We detail a series of experiments using both performance and electrophysiological measures to test these proposals. Event-related brain potentials (ERPs) will be recorded from the scalp of normal human subjects between the ages of 20 and 90 as they process linguistic and non-linguistic materials. The proposed experiments include manipulations of the different subcomponents of WM and/or long term memory with the specific aims of: (1) extending our findings on the effects of aging on sentences with embedded relative clauses from reading to speech; (2) determining whether the elderly do indeed have problems with language comprehension because of the demands that sentence processing makes on consolidation processes in working memory; (3) testing the hypothesis that the elderly will differ from the young in anaphoric reference to the extent that pronoun resolution is implausible, thereby requiring inhibition of a prior expectation; (4) examining the hypothesis that inhibitory processes become slower and/or less efficient with advancing age by investigating negative priming with homophones in sentences and during a lexical decision task; (5) testing the hypothesis that the elderly have a harder time ignoring and inhibiting irrelevant stimulus attributes using a generalized """"""""2-back"""""""" working memory paradigm with non-language materials as well; (6) testing the proposal that because of less efficient inhibitory mechanisms, older individuals will show larger """"""""fan effects"""""""" than younger individuals in verifying probe items related to a series of propositions that they have been taught. This research project will refine electrophysiological markers of important cognitive functions in relation to language processing and organization of working and long-term memory in normal adults throughout life. These data can, in principle, offer guidelines on the best structure for language materials aimed at the elderly. Moreover, this normative data base should be of value for the assessment of young and old individuals with disorders of aging and language processing.
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