Prefrontal regions play a predominant role in imposing an attentional 'set': evidence from fMIRI

fMRI was used to determine whether prefrontal regions play a predominant ro le in imposing an attentional 'set' that drives selection of task-relevant information. While monitoring for an atypical item, individuals viewed Stro op stimuli that were either colored words or colored objects. Attentional d emands were varied, being greater when the stimuli contained two distinct a nd incongruent sources of information about the task-relevant attribute (e. g., when attending to color, seeing the word 'blue' in red ink) as compared to only one source (e.g., seeing the word 'late' in red ink). Prefrontal b ut not anterior cingulate regions exhibited greater activation on incongrue nt than neutral trials, suggesting that prefrontal cortex has a major role in imposing an attentional 'set'. In addition, we found that prefrontal act ivation is most likely to occur when that attentional set is difficult to i mpose. (C) 2000 Elsevier Science B.V. All rights reserved.