Attenuation of typical sex differences in the time-resolved functional connectivity of the fusiform gyrus in autism

Background Autism is characterized by social-communicative difficulties, with sex differences in symptom presentation. Social functioning is inherently dynamic, however, many neuroimaging studies rely on static, time-averaged approaches that obscure time-varying network interactions, potentially limiting our ability to capture the dynamic processes underlying social cognition. The fusiform gyrus (FFG), central to face and social perception, shows differences in functional connectivity in autism, yet is rarely examined dynamically or as a spatially heterogeneous structure. Here, we investigate the dynamic functional connectivity of FFG subregions in terms of their large-scale network configurations as a function of diagnosis and sex. Methods We applied micro co-activation patterns analysis (CAPs) to resting-state fMRI data from 286 autistic individuals (208:78 males:females) and 228 non-autistic individuals (146:82 males:females), aged 6-30 years, from the EU-AIMS LEAP dataset. CAPs were identified using k-means clustering with FFG as the seed, and connectopic mapping positioned each CAP along the principal connectivity gradient. We quantified CAPs occurrence and further examined dwell time, transition probabilities, and spatial extent, along with associations with social functioning. Results Six CAPs mapped onto distinct FFG subregions along a posterior-anterior axis. A significant sex-by-diagnosis interaction emerged for a default mode network (DMN)-related CAP. Non-autistic females exhibited significantly more frequent occurrences, longer dwell times and distinct transition dynamics compared to males, while no sex difference was observed in autism. The spatial extent of this CAP showed a reversal of typical sex effects. Conclusions Autism is associated with an attenuation and reversal of typical sex differences in the functional configuration and spatial extent of FFG-DMN coupling, indicating that neural signatures of social-cognitive functions are sex-specific and dynamic. These findings suggest that sex is a neurobiologically meaningful dimension of heterogeneity in autism, expressed in dynamic network organization.