Severity-dependent alterations in default mode network subnetwork connectivity in social anxiety disorder: an EEG study

Social anxiety disorder (SAD) is associated with excessive self-focused processing and heightened sensitivity to social threat, yet how large-scale brain networks vary across symptom severity remains unclear. The Default Mode Network (DMN), central to self-referential and internally oriented cognition, represents a key system for examining severity-related neural alterations in SAD. In this study, we investigated severity-dependent changes in DMN functional connectivity using electroencephalography (EEG). Resting-state and anxiety-loaded EEG data were collected from healthy controls and individuals with mild, moderate, and severe SAD. Functional connectivity was quantified using Phase-Locking Value (PLV) across multiple frequency bands and analyzed within anatomically defined DMN subnetworks, including frontal, fronto-parietal, posterior, and interhemispheric components. The results revealed systematic, severity-dependent alterations in DMN connectivity. At rest, alpha-band synchronization within frontal and posterior DMN hubs was relatively preserved, whereas fronto-parietal and interhemispheric connectivity progressively declined with increasing SAD severity, particularly in higher-frequency bands. Under anxiety-loaded conditions, these alterations were amplified, with pronounced reductions in long-range connectivity while core DMN hubs remained comparatively resilient.