Electrophysiological Evidence for Impaired Control of Motor Output in Schizophrenia.

Previous research has demonstrated pervasive deficits in response-related processing in people with schizophrenia (PSZ). The present study used behavioral measures and event-related potentials (ERPs) to test the hypothesis that schizophrenia involves specific impairment in the ability to exert control over response-related processing. Twenty-two PSZ and 22 matched control participants completed a choice response task in counterbalanced testing sessions that emphasized only accuracy (the unspeeded condition) or emphasized speed and accuracy equally (the speeded condition). Control participants successfully modulated behavioral and ERP indices of response-related processing under speed pressure, as evidenced by faster and less variable reaction times (RTs) and an earlier onset and increased amplitude lateralized readiness potential (LRP). By contrast, PSZ were unable to improve RT speed or variability or to modulate the LRP under speed pressure, despite showing a decrease in accuracy. Notably, response-related deficits in PSZ emerged only in the speeded condition; behavioral and ERP measures did not differ between groups in the unspeeded condition. Together, these results indicate that impairment in the ability to exert control over response-related processing may underlie response-related deficits in schizophrenia.