Event-related potential P3 elicited by a single tone in personality disorders

Background: A cerebral P3 potential (passive P3) in response to a single tone shares similar morphology to the classical P3 elicited in the active "oddball" paradigm, but reflects passive attention. As the patients with schizotypal, antisocial and borderline personality disorders showed reduced amplitude and prolonged latency of classical P3, it is reasonable to expect that these patients might show an abnormal passive P3. In order to test this hypothesis, we tried the single tone elicited event-related potentials (ERPs) in patients with several sorts of personality disorders. Methods: We tested the passive ERPs in 205 patients with personality disorders (22 patients with the paranoid type, 11 schizoid, 14 schizotypal, 18 antisocial, 18 borderline, 16 histrionic, 20 narcissistic, 27 avoidant, 30 dependent and 29 obsessive-compulsive) and in 30 healthy volunteers. Their Axis I symptoms of depression and anxiety were measured by Zung's Self-rating Depression Scale and Self-rating Anxiety Scale. Results: Both schizoid and paranoid groups showed significantly reduced P3 amplitude. In addition, the schizoid group showed significantly shorted N1 latency and enhanced N2 amplitude. Most patient groups except schizoids scored higher on the Depression or Anxiety scales, or both, but the ERP findings were not correlated with the Axis I symptoms in any given group alone. Conclusions: The abnom1al negative components implied a higher vigilance or cortical arousal level in the schizoid patients, while the reduced P3 amplitude indicated a poorer passive attention in both schizoid and paranoid patients.