[Community-informed connectomics of cortical intrinsic organization in subjective cognitive decline]

Objective: To investigate the intrinsic organization of cortical circuitry in individuals with subjective cognitive decline (SCD) via resting-state functional magnetic resonance imaging (rs-fMRI) connectome analysis and its correlation with cognitive level. Methods: From June 2017 to November 2019, thirty-six middle-aged and elderly individuals with complaints of memory decline and 32 normal controls (NC) were enrolled from communities in Nanjing. We collected cognitive scale performance,T₁-weighted imaging (T₁WI) and rs-fMRI data of all subjects. There were 5 males and 31 females in the SCD group, with an average age of (64±5) years. In the NC group, there were 8 males and 24 females, with an average age of (65±5) years. Preprocessing of rs-fMRI data was conducted, then the cerebral cortex was divided into 333 cortical parcels (nodes) and 10 predefined communities according to the prior template. Further, we established full connection matrices between cortical parcels and calculated the within-module degree (WMD) and participation coefficient (PC) of each node based on the matrices. The WMD and PC values were compared between the SCD and NC groups,and their correlations with cognitive scale performance were analyzed. Results: Compared to the NC group,the SCD group showed increased WMD in the dorsolateral prefrontal cortex (DLPFC)(P<0.05,FDR corrected) and the middle frontal gyrus (P<0.005,uncorrected) of the right frontoparietal network (FPN). The SCD group also showed decreased WMD(P<0.05,FDR corrected) in the superior occipital gyrus of the left visual network (VN) and decreased PC (P<0.005,uncorrected) in the supramarginal gyrus of the left dorsal attention network (DAN). The WMD values in the DLPFC showed significant positive correlations with the auditory verbal learning test (AVLT)short-delayed memory (r=0.364,P=0.029),recognition memory (r=0.364, P=0.029) and the Boston naming test scores (BNT, r=0.356, P=0.033)in the SCD group. The PC values in the supramarginal gyrus were significantly positively correlated with the BNT scores (r=0.413, P=0.012) in the SCD group. Conclusion: Cortical network imbalance and reconstruction characterized by decreased intra-module connectivity of VN and inter-module connectivity of DAN exist in SCD subjects,while increased intra-module connectivity of FPN may serve in a compensatory way for the early cognitive decline.