The proposal continues a research program aimed at elucidating the cognitive and neural bases of memory for the core content of an experience (item memory) which shows moderate age-related declines, versus memory for the context of an experience (source memory) which shows larger age-related declines. The methods we apply are behavior, event-related potentials (ERPs), and diffusion-tensor MR imaging (DTI). Most studies compare older and younger adults, but we also emphasize variability among older adults, and examine relationships between performance in experimental memory paradigms, neuropsychological measures, ERPs, and measures of white matter integrity. 1. Multiple experiments are designed to characterize the conditions which improve or worsen source memory performance in older adults. Selection of conditions is guided by the hypothesis that these are conditions which reduce the burden on prefrontal/executive functions, so that many of these experiments simultaneously test hypotheses about prefrontal function. Adjunct hypotheses are that older adults will prove more sensitive to the experimental manipulations than young, and that those particular older adults whose neuropsychological profile suggests poorer prefrontal/executive function will prove most sensitive. Some experiments manipulate encoding conditions (including emotional arousal) because some older adults (those with weaker executive skills) may fail to spontaneously select optimal encoding strategies. Alternatively, it may be the case that encoding strategies which lead to tighter binding of different aspects of an event into a unitary memory trace are less demanding of executive resources at retrieval. Retrieval conditions which may alleviate or exacerbate the source memory deficit in older adults are also manipulated;these include interference during the test phase, and the provision of external cues to aid in sequencing memory operations. 2.
A second aim i s to examine criterion setting, and evaluation of stimuli with respect to a criterion, as candidate """"""""prefrontal executive functions"""""""" necessary for successful performance of some memory tasks. 3.
A third aim i s to characterize relationships between prefrontal and more posterior brain activity, with the hypothesis that these will be qualitatively different in older and younger adults, and may sometimes reflect an effort to compensate for failing memory via increased prefrontal engagement. 4. Finally, we examine one neurobiological hypothesis about age-related deficits in complex memory tasks (such as source memory), namely that a breakdown in connectivity between prefrontal and posterior brain regions may be apparent in DTI measures, and correlate with behavioral measures of executive function and prefrontal ERPs.
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