• Obsessive-compulsive disorder;
  • Event-related potentials;
  • Processing negativity;
  • N200;
  • P300;
  • Overfocused attention


A hypothesis of overfocused attention in obsessive-compulsive disorder was investigated by measuring auditory event-related potentials (ERPs) during a selective attention task. Unmedicated patients (n= 18) with this disorder showed significantly larger attention-related processing negativity (PN), with earlier onset and longer duration, than did normal controls (n= 15). In the N200 region (160–250 ms), PN was larger in patients with fewer nonspecific neurological soft signs. This task, however, did not yield any group differences in mismatch negativity (N2a) or classical N200 (N2b). P300 amplitudes for attended targets were smaller for patient than normal groups, but the reverse was true for P300 and positive slow wave amplitudes for unattended nontargets. Collectively, these ERP abnormalities suggest a misallocation of cognitive resources. Because of the importance of the frontal lobe in the control of selective attention, PN enhancement in patients with obsessive-compulsive disorder may reflect hyperactivation of this region. This conceptualization is consistent with recent functional neuroimaging findings.