Resting-State EEG Theta-Band Functional Connectivity Characterizes Heterogeneity in Internet Gaming Disorder

Abstract Background. Symptom-based assessments capture IGD severity but provide limited information about neurophysiological heterogeneity. We examined whether resting-state EEG amplitude envelope correlation (AEC) profiles relate to IGD symptoms and reveal connectivity-defined heterogeneity. Methods. Thirty participants with IGD and thirty healthy controls underwent five-minute eyes-closed resting-state EEG. Source-level AEC was estimated across theta, alpha, beta, and gamma bands. Exploratory representational similarity analysis tested associations between connectivity-profile dissimilarity and IGD-20 differences; theta-AEC profiles within IGD were further examined using principal component analysis and k-means clustering. Results. Within IGD, theta-AEC dissimilarity was associated with mood-modification differences ( rₛ = 0.277, p FDR = 0.020), whereas the corresponding association in controls was not significant. Exploratory clustering indicated connectivity heterogeneity, with the largest difference involving Visual–Salience/Ventral Attention connectivity; clusters did not differ in IGD-20 scores or weekly gaming time. Conclusions. Theta-AEC may capture symptom-related neurophysiological variation within IGD.