524. DISTINCT SIGNATURES OF OSSOS COMPARED TO SSDS AND HC USING GRAPH THEORY ANALYSIS

Abstract Background No studies have explored the differences in topological properties of resting-state fMRI (rs-fMRI) between patients with Other Specified Schizophrenia Spectrum and Other Psychotic Disorders (OSSOs) and Schizophrenia Spectrum Disorders (SSDs). Aims & Objectives This study aimed to investigate these differences in functional brain connectomes using a graph theory approach. Method We recruited 86 OSSOs, 77 SSDs, and 83 healthy controls (HCs) matched for age, sex, and education. OSSOs were further divided into subgroups: those with stable diagnoses for over one year (OSSOs ≥1-year) and those with pure delusion (PD). Global and local network metrics were obtained via graph-based rs-fMRI analysis, with Network-Based Statistic (NBS) performed as ancillary analysis. Results Both OSSOs and SSDs showed intact global network properties but exhibited higher global functional connectivity strength and hyperconnectivity within an interconnected component compared to HCs. For local metrics, OSSOs had significantly higher betweenness centrality in the right thalamus than SSDs and HCs, while SSDs showed increased betweenness centrality in the right thalamus compared to HCs. Subgroup analysis showed that OSSOs ≥1-year, PD, and SSDs maintained intact global metrics but exhibited higher global functional connectivity strength and hyperconnectivity relative to HCs. Although the betweenness centrality of the right thalamus was significantly higher in PD than in SSDs and HCs, SSDs demonstrated a higher nodal clustering coefficient in the left middle temporal gyrus compared to OSSOs ≥1-year and HCs. Discussion & Conclusions In the OSSOs, the thalamus exhibited higher betweenness centrality, and the left middle temporal gyrus (MTG.L) showed a lower nodal clustering coefficient compared to SSDs. These findings indicate potential network biomarkers for differentiating OSSOs from SSDs. Additionally, they may support the hypothesis that OSSOs should be regarded as a distinct clinical syndrome with a unique neural network.