The goal of the proposed research is to improve our understanding of memory and language dysfunctions in the early stages of Alzheimer's disease (AD) by assessing the nature of changes in the representations of knowledge that subserve perception, language, and memory. Such changes are manifested in speeded or biased responses to stimuli following exposure to those stimuli: The facilitated performance is termed priming. The proposed research derives from a new three-level model of priming that identifies separable learning processes supporting distinct components of vision and language. The model is motivated by memory-systems analyses that relate specific kinds of learning to separable neural systems on the basis of spared and impaired learning capacities in patients with global amnesia or AD. The model postulates three dissociable levels of priming: (1) perceptual-structural priming, reflecting visuoperceptual learning processes intact in amnesia and in AD; (2) lexical-semantic priming, reflecting semantic-retrieval learning processes intact in amnesia and impaired in AD; and (3) event-fact priming, reflecting contextual learning processes impaired in amnesia and in AD. The model generates four hypotheses which we propose to test over five years in seven multi-experiment studies with 100 mildly-to- moderately demented AD patients and 100 normal control subjects. The newly obtained empirical evidence will guide us in restructuring our integrative model of priming functions in normal subjects and priming dysfunctions in AD patients. In turn, the revised model will improve our understanding of the functional organization of the neural systems that subserve normal perception, language, and memory, and may reveal how damage to those systems leads to dementia in AD. The elaboration of a theoretical framework that is well supported by empirical evidence should be useful in the development of valid and sensitive behavioral testing instruments for assessing the efficacy of putative cognition- enhancing drugs in AD and other age-related neurological diseases.
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