Semantic processing impairment in individuals with schizotypal personality disorder features: a preliminary event-related potential study.

OBJECTIVE This study aimed to examine semantic processing features in individuals with and without schizotypal personality disorder (SPD) features. METHODS An implicit semantic task was used to examine the automatic spreading semantic activation process which is relatively free from the influence of attention. An explicit semantic task was used to examine the controlled semantic processing which requires high involvement of attention. Individuals with stable SPD features (n=17) were those who scored higher than 36 on the schizotypal personality questionnaire (SPQ) at two time points. Individuals with unstable SPD features (n=15) were defined as participants who scored higher than 36 at the baseline time point but lower than 36 at the second time point. Their performances in the two semantic tasks were then compared to 17 individuals without SPD features (scoring below 36 at both time points). Event-related potentials (ERP) were recorded when participants were performing the two tasks. RESULTS Behavioral data, early ERP components and N400s were analyzed in each experiment. No between-group difference was observed in the implicit semantic task. In the explicit semantic task, the differences involved only the N400 component. When compared to the group without SPD features, participants with stable and unstable SPD features showed enhanced N400 effects (difference wave), while there was no difference between the two groups with SPD features. Moreover, the larger N400 effects were found to be due to less negative N400 amplitudes to related target words. CONCLUSION These findings suggest that individuals with SPD features were impaired in processing of context-related stimuli. The inhibition function to contextually unrelated materials in participants with SPD features appeared intact.