Correlation between P50 suppression and psychometric schizotypy among non-clinical Japanese subjects

The link between P50 suppression and psychometric schizotypy was previously reported in non-clinical English-speaking subjects; however, whether a similar relationship exists within a different ethnic sample is unknown. Furthermore, whether such a relationship can also be accounted for by such basic personality characteristics as extraversion or neuroticism has not yet been reported. In the present study, we investigated the correlations of P50 suppression with psychometric schizotypy, and with extraversion or neuroticism among non-clinical Japanese. Subjects were 34 healthy volunteers. The auditory P50 potential was obtained using a paired stimulus paradigm. Psychometric schizotypy was assessed using schizotypal personality questionnaire (SPQ). Extraversion and neuroticism were assessed using Maudsley personality inventory (MPI). P50 suppression correlated not only with total SPQ score, but also with extraversion and with neuroticism. However, the partial correlation analysis revealed a significant partial correlation of P50 suppression with SPQ when controlled for extraversion or neuroticism, and a non-significant partial correlation of P50 suppression with extraversion or neuroticism when controlled for SPQ. When subjects were divided into two subgroups according to the mean SPQ score, the degree of P50 suppression was lower in the high than in the low SPQ scorers. Our results indicate that P50 suppression is one of the neurobiological substrates underlying psychometric schizotypy, and that this relationship cannot be accounted for by measures of extraversion or neuroticism.