Paranoid induction reduces N400s of healthy subjects with delusional-like ideation.

A previous study suggests that the amplitude of the N400 event-related potentials (ERPs) of healthy subjects does not vary with their delusional-like ideations. This contrasts with the smaller N400 amplitudes observed in more- than in less-deluded schizophrenia patients. Here, we hypothesize that these smaller N400 amplitudes were related to the paranoid feelings patients had during the ERP recording. We thus induced this type of feelings in healthy subjects. Delusional-like ideation was assessed with the schizotypal personality questionnaire. Thirty-four healthy subjects completed a semantic categorization task. Paranoid feelings were significantly enhanced by the induction. In these conditions, greater delusional-like ideation scores were associated with smaller N400 amplitudes and larger late positive components. Controlling for the two other schizotypal factors strengthened these results. These findings may help us understand why delusions persist.