Trait and state aspects of internal and external performance monitoring in schizophrenia.

Disturbed internal performance monitoring has been repeatedly demonstrated in schizophrenia. Along with internal monitoring, efficiently processing external task-relevant performance feedback that goes unnoticed by the internal monitoring system is crucial for adequate performance. It is unknown whether external monitoring is disturbed in schizophrenia and whether it is trait or state dependent. The current study investigated the effects of treatment on both internal and external performance monitoring in schizophrenia. Twelve schizophrenia patients and twelve matched healthy controls performed a modified flanker task while ERPs and behavioral measures were obtained. Both groups were assessed twice, with a six-week interval, during which the patients received antipsychotic treatment. Internal monitoring was investigated by means of the response-locked error-related negativity (Ne/ERN), an event-related potential component elicited by erroneous responses. External monitoring was investigated by analyzing the feedback-locked P300 elicited by task-relevant external response-time feedback (late feedback). Compared to controls, schizophrenia patients showed diminished Ne/ERN amplitudes, which were insensitive to six weeks of treatment. Patients also had reduced P300 amplitudes in response to late feedback at the first assessment, but these were normalized at the second assessment. Also, patients showed increased performance following negative external feedback at the second session. This study demonstrates the importance of considering both forms of performance monitoring in schizophrenia. Diminished internal error processing seems to be an important 'trait' marker of the disorder, while processing of externally presented feedback appears to have a 'state' character, susceptible to treatment at both a neurophysiological and a behavioral level.