Investigating Effective Connectivity within the Default Mode Network in Autism Spectrum Disorder: Insights from Dynamic Causal Modeling of Resting-State fMRI

Autism Spectrum Disorder (ASD) is characterized by deficiencies in social interactions and communications. The default mode network (DMN) is a resting-state network implicating in the social-cognitive deficits observed in ASD. Studying brain connectivity within the DMN in a large group can reveal useful insights into the mechanisms of ASD. This study investigated effective connectivity (EC) within the DMN, including the right and left middle temporal cortex ($\mathrm{r} / \mathrm{l}$ MTC), right and left hippocampus, posterior cingulate cortex, medial prefrontal cortex, and right and left inferior parietal cortex (r/l IPC), using spectral dynamic causal modeling. A large sample size from the ABIDE database was used, comprising 1281 participants (577 ASD, aged 5-60 years; 704 typically developing controls (TC), aged 5-57 years). Group-level analysis was conducted using Parametric Empirical Bayesian (PEB) method. The effects of sex, eye status during scanning, age, and Full-scale Intelligence Quotient (FIQ) on EC in ASD and TC groups were assessed. Results revealed significant group differences in EC from rIPC to IMTC, with decreased inhibition in ASD compared to TC. Additionally, a significant correlation was found between this EC and clinical scores (ADOS_G_TOTAL and ADOS_G_SOCIAL). Significant effects of sex and eye status on EC were observed in both groups, with differing patterns. In contrast, No association was found between age and EC, nor between FIQ and EC. In conclusion, this study highlights the alteration of EC in the DMN and underscores the importance of considering sex and eye status in EC studies of ASD.