Effects of Aging on Recollection, Familiarity, and Conceptual Priming

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DESCRIPTION (provided by applicant): A major goal in cognitive neuroscience of aging is to identify the neural bases of cognitive abilities that are impaired vs. spared by aging. Recollection is the form of memory most impaired by healthy aging and Alzheimer's Disease. Recollection refers to vividly remembering a past event including its associated contextual details, and it differs from familiarity, which refers to the vague feeling that the event occurred in the past even though details cannot be retrieved. Behavioral studies have provided strong evidence that older adults are impaired in recollection but largely unimpaired in familiarity (for a review, see Yonelinas, 2002). Very little is known about the neural bases of this dissociation. In young adults, recollection has been shown to be more dependent on the hippocampus and prefrontal cortex (PFC), while familiarity is more dependent on the rhinal cortex. However, it is unclear whether age-related declines in recollection are primarily mediated by hippocampal or PFC dysfunction. Furthermore, it is uncertain whether the sparing of familiarity is related to the preservation of conceptual priming, a form of implicit memory in which memory performance is facilitated by previous exposure to semantically-related information. The proposed study integrates three methodological approaches to investigate the scope and limits of impaired and preserved episodic memory processes in older adults. First, functional magnetic resonance imaging (fMRI) is used to determine whether older and younger adults use similar or different brain regions during recollection, familiarity, and conceptual priming. Second, diffusion tensor imaging (DTI) is used to quantify white matter integrity in pathways linking regions of interest. Finally, a test battery is used to assess individual differences in neuropsychological status (NS) and determine whether varying levels of executive and memory function can account for differences in task performance and in associated brain activity. These three approaches will be used together to investigate each question of interest. The proposed project is significant for several reasons. Although PFC dysfunction is assumed to play a major role in cognitive aging, the contribution of this region to memory deficits in older adults is still uncertain. In addition, the rhinal cortex is one of the first sites of Alzheimer's Disease neuropathology; thus, understanding its precise role in memory is an important step in distinguishing healthy aging from pathological aging. Moreover, if we can show that the reengagement of conceptual information during measures of familiarity is used to influence and improve memory judgments, then this offers a potential avenue for cognitive training and rehabilitation. Thus, investigating these questions is important at both basic and applied levels. PUBLIC HEALTH RELEVANCE: The rhinal cortex is one of the first sites of Alzheimer's Disease neuropathology; thus, understanding its precise role in memory is an important step in distinguishing healthy aging from pathological aging. Moreover, if we can show that the reengagement of conceptual information during measures of familiarity is used to influence and improve memory judgments, then this offers a potential avenue for cognitive training and rehabilitation. Thus, investigating these questions is important at both basic and applied levels.