The processing of attended and nonattended stimuli in schizophrenic patients was examined with event-related potentials (ERPs) in a lexical decision task. In positive semantic and repetition priming the N400 amplitude did not differ between a group of 17 medicated schizophrenic patients and a group of 20 matched healthy controls. However, negative priming affected the N400 only in controls. Reaction time effects were dissociated from these ERP effects, with patients showing stronger positive priming than controls but identical negative priming. The semantic processes related to the N400 appear to be intact in schizophrenic patients, but patients seem to incorporate less context information (about the nonattended prime) in their episodic memory traces. A stronger increase of the posterior late positive complex in parallel to the stronger positive priming in schizophrenic patients may reflect relatively stronger automatic memory retrieval processes in patients.
