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Abstract:
Abstract: Working memory studies with rhesus monkeys show
that there are some cells in the dorsolateral prefrontal cortex
(DLPFC) which support mnemonic activity during the delay period of
a delayed-response task (DRT). Furthermore, lesions in the DLPFC
lead to severely impaired working memory function as well as
symptoms that resemble schizophrenia such as increased
distractibility and perseveration. Previous DRT studies show that
schizophrenia patients have spatial working memory deficits. The
current study probed the effects of spatial and temporal
distractors during the delay of a DRT. Participants were required
to remember target location while ignoring a distractor that was
presented in one of several locations in the same or opposite
hemifield as the target. Distractor onset was t=0 (simultaneous
with target presentation), 1000, 5000, 8000, or 9000 ms
(simultaneous with response template). Both schizophrenia patients
and controls showed greater error distances for t=0 than t=9000
distractors, but error patterns for intermediate onset times
differed between groups. Specifically, schizophrenia patients'
accuracy diminished with early distractor onset whereas controls'
accuracy did not. This concurs with a previous finding that working
memory performance in monkeys was disrupted only if electrocortical
stimulation to the DLPFC occurred early in the delay (Stamen 1985).
Current analysis of distractor location shows that both groups
performed worse when the target and distractor were in opposite
hemifields.
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