Effects of moderate alcohol levels on default mode network connectivity in heavy drinkers

Background It is well established that even moderate levels of alcohol affect cognitive functions such as memory, self‐related information processing, and response inhibition. Nevertheless, the neural mechanisms underlying these alcohol‐induced changes are still unclear, especially on the network level. The default mode network (DMN) plays an important role in memory and self‐initiated mental activities; hence, studying functional interactions of the DMN may provide new insights into the neural mechanisms underlying alcohol‐related changes. Methods We investigated resting‐state functional connectivity (rsFC) of the DMN in a cohort of 37 heavy drinkers at a breath alcohol concentration of 0.8 g/kg. Alcohol and saline were infused in a single‐blind crossover design. Results Intranetwork connectivity analyses revealed that participants showed significantly decreased rsFC of the right hippocampus and right middle temporal gyrus during acute alcohol exposure. Moreover, follow‐up analyses revealed that these rsFC decreases were more pronounced in participants who reported stronger craving for alcohol. Exploratory internetwork connectivity analyses of the DMN with other resting‐state networks showed no significant alcohol‐induced changes, but suffered from low statistical power. Conclusions Our results indicate that acute alcohol exposure affects rsFC within the DMN. Functionally, this finding may be associated with impairments in memory encoding and self‐referential processes commonly observed during alcohol intoxication. Future resting‐state functional magnetic resonance imaging studies might therefore also investigate memory function and test whether DMN‐related connectivity changes are associated with alcohol‐induced impairments or craving. Our study investigated the effects of alcohol (ALC) on functional brain connectivity in 37 heavy drinkers. Compared to saline (SAL), moderate alcohol exposure (0.8 g/kg) significantly decreased the functional connectivity of two brain areas within the default mode network (DMN). The DMN is a brain system implicated in memory processes and self‐initiated mentation. It is active when we are awake but resting. Our findings help explain dysfunctions in episodic memory encoding and self‐referential processing apparent after moderate alcohol consumption.