ACC-related functional circuit organisation across static, dynamic and directed connectivity in internet gaming disorder.

The anterior cingulate cortex (ACC) coordinates internally oriented, salience-related and control processes, and hence may be involved in addictive behaviours. Its role in internet gaming disorder (IGD) remains unclear. We therefore seek to determine whether ACC-related circuits show convergent alterations across complementary levels of functional organisation in IGD. Resting-state functional magnetic resonance imaging (fMRI) data from 45 participants endorsing at least five DSM-5 IGD criteria and 45 matched healthy controls were analysed using all four atlas-defined ACC subregions as seeds to account for the functional heterogeneity of the ACC. We first mapped static functional connectivity differences. Next, we tested whether the implicated pathways showed altered temporal variability using sliding-window dynamic functional connectivity, characterised recurring seed-to-parcel connectivity states, and estimated directed effective connectivity using spectral dynamic causal modelling with parametric empirical Bayes. Compared with healthy controls, individuals with IGD showed reduced static connectivity between the dorsal ACC and two left precuneus clusters, and between the subgenual ACC and a posterior medial calcarine/precuneus cluster. Primary dynamic analyses revealed reduced variability in dorsal ACC connectivity with the left inferior frontal gyrus and left medial superior frontal gyrus, increased variability in subgenual ACC connectivity with the left precuneus/cuneus, and greater occupancy of a ventral attention/default mode-dominant connectivity state. Spectral dynamic causal modelling indicated weaker directed influence from the subgenual ACC to the posterior medial node and from this node to the left inferior frontal gyrus. Together, these findings delineate multilevel alterations in ACC-related posterior medial and frontal control circuitry in IGD, suggesting disrupted coordination across static, dynamic, state-based, and directed dimensions of intrinsic brain organisation.