State dependent changes in error monitoring in schizophrenia.

The aim of this study was to determine if error negativity/error-related negativity (N(e)/ERN), error positivity (P(e)), correct response negativity (CRN) or correct response positivity (P(c)) amplitude are influenced by state changes in schizophrenia. Event-related potentials (ERPs) were recorded from nine schizophrenic patients while they performed a simple go/no-go task during the early stages of an acute episode and again following 6 weeks of treatment with antipsychotics. ERPs were also recorded from nine healthy participants while they performed the same task. Response-locked potentials were computed for errors of commission and for correct responses. Scores for reality distortion syndrome, psychomotor poverty syndrome and disorganization syndrome were determined for the schizophrenic participants before and after treatment using the Signs and Symptoms of Psychotic Illness (SSPI) Scale. N(e)/ERN amplitude was significantly reduced, compared with that in healthy participants, in the schizophrenic patients when acutely ill, and increased significantly following treatment. N(e)/ERN amplitude remained significantly larger in the healthy group than in the patients with schizophrenia after treatment. This study suggests that N(e)/ERN and CRN amplitude are modulated by clinical state in schizophrenia and provides further support to findings that decreased N(e)/ERN amplitude is a potentially useful trait marker for schizophrenia, while P(c) and P(e) amplitude are not abnormal.