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Abstract:
Abstract: Two patients with focal anterior cingulate cortex
lesions (D.L. - right caudal ACC, R.N. - left rostral ACC) were
tested in a behavioral task designed to investigate error
processing and advance configuration of task set. Age matched
normal subjects participated as controls. On each trial, subjects
responded under time pressure to a target stimulus using one of two
stimulus-response mappings, indicated by a cue presented at two
different stimulus onset asynchronies (short and long cue SOA).
Erroneous responses could be corrected with a second response
within 1600 ms. In one condition, visual feedback was available
right after the initial response, in another condition, the
feedback was delayed by 800 ms. Proportions of errors corrected
within 800 ms (early corrections) and later (late corrections) in
the two conditions were compared to assess the ability to detect
and compensate for errors. Both patients relied on external
feedback for error correction to a greater extent than controls,
suggesting a deficit in the internal monitoring of performance. In
addition, D.L. showed a disproportionately large increase in
reaction time when shifting between response mappings. R.N., on the
other hand, failed to show a benefit in accuracy and reaction time
for long cue SOA. The results are discussed in the context of
current views on ACC involvement in response monitoring and
executive control of attention.
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