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Abstract:
Single-trial list learning was used to evaluate the
neurophysiological effects of normal aging on non-verbal memory
function. Thirteen young and 10 elderly healthy volunteers (23.6
± 2.4 and 69.6 ± 6.5 years, respectively) were
scanned with
15
O-H
2
O PET while viewing successive lists of novel, nondescript line
figures. Test blocks were interleaved between study lists to obtain
old/new judgments to test figures. The regional blood flow (rCBF)
response to an effective memory challenge (EMC) was compared to
rCBF in two baseline conditions. For individual subjects, list
length for EMC was determined during practice as the maximum length
at which 75% recognition accuracy was achieved. Baseline M1
consisted of single-item study lists. Non-memory baseline NM
consisted of single-item study lists that repeated the same
nonsense figure. Mean list lengths for the young and elderly were
15.8 ± 2.9 and 5.9 ± 2.1, respectively. Every subject
in each age group revealed significant incremental increases in
right hemisphere, medial temporal rCBF from NM to M1 to EMC (p <
.001). The main group differences did not occur in medial temporal
areas, but instead appeared as incremental increases (p < .001)
in elders rCBF in the right hemisphere insular cortex and basal
ganglia. These results suggest that single-trial list learning may
reveal compensatory memory functions that operate in normal
aging.
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