Abstract

Recognition memory and the dissociation of immediate and delayed recognition in schizophrenic patients were investigated using event-related potential (ERP) and a continuous word recognition task. Fourteen schizophrenic patients and 14 age and gender matched control subjects participated. Among 240 stimulus words, 40 words were not repeated, 100 were repeated immediately and 100 were repeated after 5 intervening words. Both schizophrenic and control groups responded faster to words repeated immediately than to words repeated after a delay and to first-presented words. However, schizophrenic patients responded less accurately to words immediately and to words repeated after a delay than the controls. In terms of ERP, schizophrenic patients showed significantly reduced N200, LPC and N400 amplitudes, and a more frontally distributed N200 topography than the controls. For controls, immediate repetition was associated with a large LPC amplitude and the absence of N400, while delayed repetition was associated with a small LPC amplitude and the presence of N400. However, this association between immediate and delayed repetition was not observed in schizophrenic patients. All of these results indicate that schizophrenic patients have recognition memory impairment, the cause of which may range from early encoding, and memory search to late retrieval.