The anterior cingulate cortex (ACC) in patients with obsessive-compulsive disorder (OCD) has been found to be hyperactive at rest, during symptom provocation, and after commission of errors in cognitive tasks. This hyperactivity might reflect an abnormality in conflict detection, a hypothesized basic mechanism for the action-monitoring function of the ACC. This hypothesis was tested using functional magnetic resonance imaging, by scanning 11 OCD patients and 13 matched control subjects while they performed a version of the continuous-performance task with four trial types that induced graded levels of response conflict. Although a behavioral index of conflict (i.e., accuracy) was similar for patients and control subjects, the ACC activation was increased in patients during high-conflict trials. The error-related activity in the same brain region was also higher in patients, consistent with previous electrophysiological findings. Both conflict- and error-related activity showed trends for positive correlations with severity of OCD symptoms, but not with anxiety. These findings suggest that as part of an overactive action-monitoring system, the ACC is more directly involved in the pathophysiology of OCD than previously thought.
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