T39. IMPAIRED SENSORIMOTOR GATING USING THE ACOUSTIC PREPULSE INHIBITION PARADIGM IN INDIVIDUALS AT A CLINICAL HIGH RISK FOR PSYCHOSIS

BACKGROUND: Many robust studies on prepulse inhibition (PPI) were conducted in patients with schizophrenia, and, increasingly, evidence has indicated individuals who are at clinical high risk for psychosis (CHR). The specificity of the PPI is insufficient with the classic paradigm. The current study investigated an improved perceived spatial separation PPI (PSSPPI) paradigm in CHR individuals, compared with patients of first-episode schizophrenia (FES) and healthy controls (HC), and the relationship between PPI, demographics, clinical characteristics, and cognitive performance. METHODS: We included 53 FESs, 55 CHR individuals, and 53 HCs. CHRs were rated on the Structured Interview for Prodromal Syndromes (SIPS). The prepulse inhibition measures of perceived spatial co-location PPI (PSCPPI) and PSSPPI paradigms were applied using 60- and 120-ms lead intervals. The MATRICS Consensus Cognitive Battery (MCCB) was used to assess neurocognitive functions. RESULTS: Compared with HC, the CHR group had lower PSSPPI level (ISI=60 ms, P<0.001; ISI=120 ms, P<.001). PSSPPI showed a large effect size (ES) between CHR and HC (ISI=60 ms, ES=0.91; ISI=120 ms, ES=0.98); on PSSPPI using 60-ms lead interval, ES ranged from small to large from CHR to FES. PPI deficits in CHR were unrelated to demographics, clinical characteristics, and cognition. DISCUSSION: CHR individuals show a sensorimotor gating deficit similar to FES patients on PSSPPI of the startle response, with greater sensitivity than the classic PPI paradigm. PSSPPI appears a promising objective approach for identifying individuals at clinical high risk for psychosis related to a high risk of transition to schizophrenia.