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Abstract:
In previous studies, age-related changes in the maps of
scalp-recorded P3 activity, elicited by rare targets and
task-irrelevant novel environmental sounds, pointed to age-related
changes in level of frontal lobe activity. The maps were consistent
with different brain generator activity in young and elderly
subjects. However, identification of intracerebral sources is
difficult based on surface mapping alone. Therefore, a brain source
analysis was performed to obtain estimates of the brain activity
during the time period of the P3 component. "Regional source"
probes were used to examine generator activity in six brain sectors
(left and right frontal, posterior, and temporal-hippocampal
regions). This analysis revealed both bilateral frontal and
posterior brain activity to the novel stimuli in the young, but
primarily posterior brain activity to targets. For the elderly, by
contrast, targets as well as novels elicited frontal and posterior
brain activity. These models indicate different frontal brain
activity underlying the P3 in young and old, and suggest that the
elderly continue to utilize frontal processes for stimuli that are
well categorized by the young. Moreover, they add to the evidence
that the P3 component is generated by a neural system
interconnecting widespread areas of the cortex.
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