Microstate-specific functional connectivity in alcohol use disorder using resting-state EEG

Alcohol Use Disorder (AUD) is often described as a "disconnection syndrome", reflecting neural dysfunction associated with chronic alcohol use. However, previous studies on functional connectivity of resting-state EEG (rsEEG) in AUD have reported inconsistent findings — some showing hyperconnectivity, others hypoconnectivity or no significant differences — possibly due to overlooking the brain's dynamic nature even at its resting state. Here, we examined rsEEG in 26 young adults with AUD and 35 healthy controls (HC), using microstate analysis to characterize transient brain states and to estimate functional connectivity within each state. We showed that microstate map topologies were comparable between the two groups. However, the temporal dynamics in the AUD group were biased toward microstates C and D, characterized by anterior-to-posterior configurations, within which between-channel functional connectivity differed from that of HC. Particularly within microstate C, the AUD group showed significantly reduced functional connectivity compared to the HC group in the majority of channel pairs. Moreover, compared with conventional functional connectivity estimates, microstate-specific functional connectivity yielded superior classification performance in distinguishing individuals with AUD from HC. Subsequent computation of graph-theoretical measures revealed that individuals with AUD showed less stable hub-like properties and reduced small-worldness in microstate C, indicating diminished network efficiency. Our findings suggest that transient EEG properties, exemplified by microstate-specific functional connectivity, provide informative neural markers for characterizing the impact of alcohol use on the brain.