Response activation impairments in schizophrenia: Evidence from the lateralized readiness potential


  • This study was made possible by a grant from the National Institute of Mental Health (R01MH065034) and by University of Maryland General Clinical Research Center Grant Number M01-RR-16500. E.S.K. was supported by a National Science Foundation graduate research fellowship.

Address correspondence to: Emily S. Kappenman, UC-Davis Center for Mind & Brain, 267 Cousteau Place, Davis, CA 95618. E-mail:


Previous research has demonstrated deficits in preresponse motor activity in schizophrenia, as evidenced by a reduced lateralized readiness potential (LRP). The LRP deficit could be due to increased activation of the incorrect response (e.g., failure to suppress competition) or to reduced activation of the correct response (e.g., a low-level impairment in response preparation). To distinguish these possibilities, we asked whether the LRP impairment is increased under conditions of strong response competition. We manipulated the compatibility of stimulus-response mappings (Experiment 1) and the compatibility of the target with flankers (Experiment 2). In both experiments, the patient LRP was reduced as much under conditions of low response competition as under high competition. These results are incompatible with a failure of patients to suppress competition and are instead consistent with a deficit in activating the correct response.