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Abstract:
Within left frontal cortex, there is evidence that ventral
regions near and along IFG (BA 44/45/47) are differentially
recruited during meaning-based encoding, and activity in these
regions is predictive of memory performance (Logan, et al 2000).
Using fMRI, regional activation of multiple encoding conditions was
examined to determine to what extent these relations were preserved
in healthy aging. 16 younger and 16 older adults performed three
word encoding tasks: shallow and deep incidental encoding, and
intentional encoding. Older adults recruited ventral regions
significantly less during self-initiated (intentional) encoding
compared to younger adults. This age effect was eliminated during
deep encoding conditions, suggesting that under more supportive
encoding conditions older adults can recruit frontal regions known
to predict successful memory performance to the same extent as
younger adults. Older adults also showed a relative increase in
recruitment of right frontal regions compared to younger adults
during self-initiated encoding. This pattern remained even under
supportive encoding conditions when there were no age differences
in left ventral frontal activity and is perhaps indicative of
non-selective (versus compensatory) recruitment. These results
indicate a potential double hit of aging: (1) during self-initiated
encoding older adults under-recruit frontal regions known to
predict successful memory performance compared to younger adults;
(2) when frontal regions are recruited, they may be recruited
non-selectively.
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