S86. DURATION OF UNTREATED PSYCHOSIS CORRELATES WITH BRAIN CONNECTIVITY IN ANTIPSYCHOTIC-NAïVE PATIENTS WITH FIRST EPISODE PSYCHOSIS

Abstract

S340 Poster Session III the present study we aimed to investigate the subcortical volumes and cer-ebellar grey matter volumes, as well as their structural covariance in individuals with schizotypy. Methods: Six samples consisting of 352 valid participants (mean age, 19.8 years; range, 16-28 years; 41.5% male) from 4 imaging centers were included. The T1 weighted brain images were preprocessed using the FreeSurfer software v6.0 (http://www.freesurfer.net) and SUIT toolbox (http://www.diedrichsenlab.org/imaging/suit.htm) for the calculation of subcortical volumes and cerebellar volumes, respectively. Both the Schizotypal Personality Questionnaire (SPQ) and the Chapman scales (including Social Anhedonia Scale and Physical Anhedonia Scale) were used to measure the dimensional schizotypy. We split the participants into high schizotypy according to commonly used criteria (top 10%, total score>=36 for high SPQ group, n=56; >=MEAN+1SD for high Social Anhedonia group, n=88) and low schizo-typy groups ( < 0.05) and pallidum (r =-0.37, p < 0.001) in the low schizotypy group. For the high Social Anhedonia group, we found a consistent negative correlation between cerebellar grey matter volumes and thalamus (r =-0.23, p < 0.05). However, no such correlation was found in the high SPQ group. Discussion: Although several studies have examined the brain structural changes associated with schizotypy, few have focused on the unique changes concerning the different dimensions of schizotypy. Individuals with high negative schizotypy were found to exhibit local structural changes in the caudate and the cerebellum while maintaining an intact thalamic-cerebellar connection. However, individuals with high positive schizotypy exhibited relative intact local brain volumes but disrupted thalamic-cerebellar connection. These findings provide further evidence to support different patterns of structural brain changes associated with positive and negative dimensions of schizotypy. Indeed, our results suggest that cerebellar volumes as well as thalamic-cerebellar connections may serve as risk indicators for psychosis. Background: The National Institute of Mental Health has deemed imperative to 1) fully understand the behavioral and brain mechanisms of individuals who experience first episode psychosis (FEP) and to 2) substantially reduce the duration of untreated psychosis (DUP; the time between the onset of psychosis and initiation of appropriate treatment) as shorter DUP has been associated with a better prognosis in schizophrenia (SZ). Deficits in SZ have been linked to aberrant functional connectivity among three key brain networks: the default mode (DMN), salience (SN), and central executive networks (CEN). To date, only a handful of studies have examined DUP in SZ using in-vivo neuroimaging techniques. The objective of this study is to examine the effect of DUP using resting state functional connectivity MRI (rsfcMRI) in a sample of antipsychotic-naïve patients with FEP. Methods: rs-fMRI data from 45 patients with SZ (mean age = 23 yo; 32M/13F) were used and processed using a standard preprocessing pipeline. Signal from a priori brain regions of interest from posterior cingu-late cortex (DMN), right insula (SN), and bilateral posterior parietal cortex (CEN) were extracted and correlated with the rest of the brain. Additionally, exploratory connectivity analyses were also performed: local correlation (LCOR; the average of correlation coefficients between each individual voxel and a region of neighboring voxels) and global correlation (GCOR; the average of correlation coefficients between each individual voxel and all of the voxels in the brain). To examine DUP and brain connectivity, patients were divided into 3 groups: short DUP (≤ 1month; n = 15), medium DUP (< 1 year; n = 17), and long DUP (≥ 1 year; n = 13) and groups differences were tested. DUP, as a continuous variable, was also correlated with brain connectivity across all patients. All analyses were corrected for age and gender. Results: The results are: 1) for a priori analysis, significant clusters of group differences were found in L/R postcentral (DMN), L/R middle frontal/tem-poral and L/R superior temporal (SN), left inferior temporal, right frontal pole, left supramarginal and left fusiform gyri (CEN); 2) for exploratory analyses, significant clusters of group differences were found in left superior temporal and precentral, and right frontal pole (LCOR) and in left insula and temporal pole, and left superior temporal and precentral gyrus (GCOR); and 3) correlations between DUP and brain connectivity were found across both analysis in the same regions. Across all results, a very consistent pattern of greater rs-fcMRI for shorter vs. longer DUP was observed. All analyses were corrected using voxel (p < .01, uncorrected) and cluster level correction (p < .05, FDR corrected). Discussion: Our findings of rs-fcMRI suggest that heterogeneity in SZ may relate to alterations in brain mechanisms due to a possible effect of DUP. Furthermore, these differences may be mediated by symptom severity and cognitive deficits within the disorder. Future steps will include examining the impact of DUP on response to treatment using antipsychotic medication on these same patients. Overall, these preliminary findings underscore the need to further examine and shorten DUP in psychiatric populations.