| |
Abstract:
We investigated the role of anterior cingulate and related
brain circuitry in inhibition of attention to salient, but
irrelevant peripheral stimuli by manipulating the predictive value
of flanker stimuli in a fMRI study. Seven healthy adult subjects
were scanned while performing a flanker task (Eriksen et al.,
1974). Subjects were instructed to press the left key if the center
stimulus (>) was pointing left and the right key if the center
stimulus was pointing right. Congruent and incongruent flankers
were presented on either side of the target stimulus (e.g.,
>>> > >>> or <<< > <<<).
The predictive value of the flankers was manipulated by block with
predictive blocks consisting of 70% congruent and 30% incongruent
flankers, and nonpredictive blocks consisting of 30% congruent and
70% incongruent flankers. A 4 (runs) X 2 (conditions) analysis of
variance with a contiguity threshold of 3 pixels and p < .005
was performed on the subjects' pooled data. The results showed that
during the predictive condition subjects had more difficulty on
incongruent trials than during the nonpredictive condition (514
msec and 91% accuracy vs. 505 msec and 96%, respectively).
Similarly, increased MR signal intensity was observed in
dorsolateral prefrontal, parietal and anterior cingulate cortices
during the predictive condition compared to the nonpredictive
condition.
|
