ERP ABNORMALITIES DURING SEMANTIC PROCESSING IN SCHIZOPHRENIA

To examine the neurophysiological and cognitive characteristics of tho ught disturbance in schizophrenic patients, we examined the amplitude, latency, and topography of a specific event-related brain potential ( ERP), the N400, which is elicited by semantically incongruent words an d phrases. Twelve chronic schizophrenic patients and twelve age-matche d control subjects read sentences presented visually that had either s emantically correct (e.g., 'People pray in their local church') or inc orrect endings (e.g., 'Every Sunday morning people pray in their local nest'). Relative to normal controls, schizophrenic patients had signi ficantly reduced N400 amplitude and increased latency to semantically anomalous endings. Additionally, a late positive component which follo ws the N400 was significantly reduced in amplitude in schizophrenic pa tients. However, patients and controls did not differ significantly in terms of the topographical distribution of either the N400 or its lat e positive potential, examined at 28 electrode sites. Thus, N400 topog raphy in schizophrenic patients was not accompanied by the asymmetry w hich frequently characterizes the well known auditory P300 disturbance in schizophrenic patients. We concluded that these findings may refle ct a profound disturbance in attentional processes in chronic schizoph renia.