Background: Functional brain abnormalities have been studied in AOS cases. However, the alterations of causal connectivity between brain regions in AOS remains unclear. 
Methods: Thirty-two first-episode drug-naïve AOS patients and 27 healthy controls (HC) were recruited for resting-state functional MRI scanning. The brain region with the between-group difference in Regional homogeneity (ReHo) values was chosen as a seed to perform the Granger causality analysis (GCA) and further detect the alterations of causal connectivity in AOS. Both receiver-operating characteristic analysis and probabilistic neural network were applied to test the possibility of using abnormal brain connectivity for distinguishing cases from controls. 
Results: AOS patients exhibited increased ReHo values in left superior temporal gyrus (STG) compared with HC. Significantly decreased values of outgoing Granger causality from left STG to right superior frontal gyrus and right angular gyrus were observed in GC mapping for AOS. Significantly stronger causal outflow from left STG to right insula and stronger causal inflow from right middle occipital gyrus (MOG) to left STG were also observed in AOS patients. Based on assessments of the two strengthened causal connectivity of the left STG with insula and MOG, a cross-validated probabilistic neural network model could discriminate all patients from controls with remarkable accuracy at 94.9%. 
Conclusions: Patients with drug-naïve first-episode AOS exhibit brain functional connectivity abnormalities in left STG. The alterations of directional connections in left STG may play an important role in the pathogenesis of AOS and serve as potential biomarkers for the disease.

09 - ABNORMAL CAUSAL CONNECTIVITY OF LEFT SUPERIOR TEMPORAL GYRUS IN DRUG-NAÏVE FIRST- EPISODE ADOLESCENT-ONSET SCHIZOPHRENIA: A RESTING-STATE FMRI STUDY