An Event-Related Potential Study In Schizophrenia Using The Japanese Language

Background. To evaluate the basis of any abnormalities in schizophrenics' semantic processing, event-related potentials (ERPs) were recorded in 11 schizophrenic patients and 13 healthy controls during a semantic task.Methods. In each trial, stimuli consisting of S1 (word) and S2 (nonword, unrelated word, related word, or repeated word) were presented. The subjects were required to indicate whether the pairs of words were semantically related or not, and to press a "yes" or "no" button.Results. The negativity elicited by the nonword persisted longer and the following LPC was attenuated in schizophrenia, reflecting a deficit in a retrieval process or inadequate inhibition at the convergent stage of identifying a nonword. The N400 effect for schizophrenics was reduced, which may be interpreted as reflecting that integration is poor in schizophrenia. The N400 effect for healthy controls was larger on the right than on the left hemisphere, and this laterality was also observed in schizophrenia.Conclusions. We concluded that schizophrenics have a disturbance in processes for both identification of the word and integration into the preceding context.