S76. PROACTIVE AND REACTIVE RESPONSE INHIBITION IN INDIVIDUAL WITH SCHIZOTYPY: AN ERP STUDY

BACKGROUND: Schizotypy, a subclinical group at risk for schizophrenia, have been found to show impairments in response inhibition. Recent studies differentiated proactive inhibition (a preparatory process before the stimuli appears) and reactive inhibition (the inhibition of a pre-potent or already initiated response). However, it remains unclear whether both proactive and reactive inhibition are impaired in schizotypy and what are the neural mechanisms. The present event-related potential study used an adapted stop-signal task to examine the two inhibition processes and the underlying neural mechanisms in schizotypy compared to healthy controls (HC). METHODS: A total of 21 individuals with schizotypy and 25 matched HC participated in this study. To explore different degrees of proactive inhibition, we set three conditions: a “certain” go condition which no stop signal occurred, a “17% no go” condition in which stop signal would appear in 17% of trials, and a “33% no go” condition in which stop signal would appear in 33% of trials. All participants completed all the conditions, and EEG was recorded when participants completed the task. RESULTS: Behavioral results showed that in both schizotypy and HC, the reaction times (RT) of go trials were significantly prolonged as the no go percentage increased, and HC showed significantly longer go RT compared with schizotypy in both “17% no go” and “33% no go” conditions, suggesting greater proactive inhibition in HC. Stop signal reaction times (SSRTs) in “33% no go” condition was shorter than “17% no go” condition in both groups. Schizotypy showed significantly longer SSRTs in both “17% no go” and “33% no go” conditions than HC, indicating schizotypy relied more on reactive inhibition. ERP results showed that schizotypy showed larger overall N1 for go trials than HC irrespective of condition, which may indicate a compensation process in schizotypy. Schizotypy showed smaller N2 on both successful and unsuccessful stop trials in “17% no go” conditions than HC, while no group difference was found in “33% no go” conditions for stop trials, which may indicate impaired error processing. DISCUSSION: These results suggested that schizotypy tended to be impaired in both proactive control and reactive control processes.