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Abstract:
Declines in explicit memory are common in healthy elderly,
whereas implicit memory is relatively well preserved. This pattern
of preservation and declines in cognitive skills may stem from
differential aging of their substrates. We examined age differences
in motor performance in conjunction with differential aging of
cerebral structures and cognitive resources. Healthy adults (age
22-80) performed a pursuit rotor task. Volumes of the basal
ganglia, the prefrontal cortex and the hippocampus were obtained
from MRI. The performance index was time on target (TOT). Linear
improvement was evident across trials, and across blocks. The slope
of improvement was age-invariant. However, younger participants
showed significantly longer TOT. When the influences of regional
brain volumes and working memory were taken into account, the
direct age effect on mean TOT disappeared. Instead, reductions in
the volume of the putamen, and the prefrontal cortex, mediated by
nonverbal working memory performance, predicted shorter TOT. In
contrast, neither the volume of the caudate and the hippocampus,
nor verbal working memory showed association with motor
performance. The results indicate that in healthy aging, procedural
learning is preserved, and motor performance is reduced only in
individuals with significant shrinkage in selected neostriatal and
prefrontal circuits. Working memory for visual-spatial information
is important for acquiring and maintaining a motor skill.
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