Lack of repetition priming effect on visual event-related potentials in schizophrenia

Background: The present study was designed to assess, using event-related potentials, whether aberrant semantic processing reported in schizophrenia results from primary semantic overactivation or contextual dysregulation. Methods: The visual event-related brain potentials were compared between 9 schizophrenic subjects and 16 normal control subjects performing two kinds of semantic categorization tasks with different nontarget stimuli: 1) nontargets comprising words, pseudowords, and unpronounceable foreign letters and 2) nontargets comprising initial presenting words, immediate repetition words, and delayed repetition words. Results: Schizophrenic subjects showed no evidence suggestive of a greater negative potential associated with words and pseudowords, but they did show a lack of amplitude change associated with immediately repeated words relative to that in control subjects. Conclusions: These results suggest that aberrant semantic activation in schizophrenia results mainly from a failure to utilize information from preceding words or context, and could explain the increased N400 to the congruent or related words recently reported in this disease.