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Abstract:
Consistent with previous long-term memory findings (Chalfonte
& Johnson, 1996), data from Experiment 1 showed that in a
working memory task, compared to young adults, older adults
demonstrate a disproportionate deficit remembering combinations of
features, even with equivalent memory for individual features. Such
evidence suggests age-related deficits in reflective processes
necessary for binding features into episodic memories. Neuroimaging
evidence from young adults suggests that prefrontal cortex
maintains and manipulates information (e.g., D'Esposito et al.,
1998; Petrides, 1994); electrophysiological recordings in monkeys
show some cells in prefrontal cortex code for both object and
location (Rao, Rainer, & Miller, 1997). Thus, in Experiment 2
we used FMRI to compare prefrontal activation in young and older
adults using a task that required participants to respond on the
basis of memory for either individual features or feature
combinations. Each trial consisted of three 3 X 3 grids, presented
sequentially, each containing a different object in a different
location. On different blocks of trials, young and older adults
studied, and were tested on, either object, location, or combined
object+location information. We used an event-related FMRI method
to temporally isolate neural correlates of component processes
engaged during encoding, delay, and test. Results will be discussed
in terms of age-related deficits in reflective component processes
that support long-term encoding.
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