| Disruption of self-monitoring processes has been hypothesized to be related to the neurocognitive impairments and symptoms experienced by schizophrenia patients. This study used a component of the event-related brain potential, the error-related negativity (ERN), to examine behavioral monitoring in schizophrenia patients. The amplitude of the ERN has been demonstrated to be associated with error detection and response competition. Electrophysiological data were collected while 16 relatively asymptomatic schizophrenia patients and 10 normal comparison subjects performed a choice reaction time (RT) flanker task under two instruction conditions: emphasize accuracy and emphasize speed. Schizophrenia patients showed reduced ERN amplitude compared to normal comparison subjects in error trials when instructed to focus on response accuracy. On correct trials, schizophrenia patients tended to show enhanced negativity compared to normal comparison subjects in both instruction conditions. In schizophrenia patients, error correction and increases in RT and accuracy on trials following errors were associated with larger ERNs. Normal comparison subjects also demonstrated these patterns except they showed no association between ERN size and RT on following trials. These findings suggest that although the ERN may not be as sensitive to the accuracy of responses and to task context in schizophrenia patients as it is in normal comparison subjects, the functional relationship between error-related activation and response-related behaviors is similar in the two groups. The absence of a relationship between ERN amplitude and symptom ratings in schizophrenia patients puts to question the theory that these patients are impaired in the monitoring and representation of their own mental states (Frith, 1992, 1994) although failure to observe such as association may have been due to the relatively restricted range in clinical symptoms observed in the present study. |
