EVENT-RELATED POTENTIAL INDEXES OF SEMANTIC PROCESSING IN SCHIZOPHRENIA

Event-related potentials (ERPs) were recorded while schizophrenic pati ents and healthy controls read congruous and incongruous sentences in anticipation of a memory test. The schizophrenic group performed more poorly in both recognition memory and cued recall tests. The two group s did not differ in the amplitude of the N400 component of the ERP but the difference between the ERPs to congruous and incongruous sentence s persisted longer in the schizophrenic sample. The schizophrenic samp le also showed reduced parietal positivity and a reduced effect of con gruity on the late positive component that follows N400. Within the sc hizophrenic sample, measures of attentional impairment and positive th ought disorder were correlated with mean amplitude of both the N400 an d the subsequent positivity. The results imply that the structure and spread of activation within semantic memory is not impaired in schizop hrenia. Rather, impairments appear to lie in processes required to int egrate activated information with the current context.