Dorsal anterior cingulate glutamate is associated with engagement of the default mode network during exposure to smoking cues

- The default mode network (DMN) is involved in internally focused cognition.
- We show less DMN suppression when nicotine-dependent smokers view smoking cues.
- The dorsal anterior cingulate cortex (dACC) may play a role in modulating the DMN.
- We show an association between dACC glutamate and DMN reactivity to smoking cues.

BackgroundWhen exposed to smoking cues, nicotine dependent individuals activate brain regions overlapping with the default mode network (DMN), a network of regions involved in internally-focused cognition. The salience network (SN), which includes the dorsal anterior cingulate cortex (dACC), is thought to interact with the DMN and aids in directing attention toward salient internal or external stimuli. One possibility is that neurochemical variation in SN regions such as the dACC impact DMN reactivity to personally relevant stimuli such as smoking cues. This is consistent with emerging evidence suggesting an association between midline cortical glutamate (Glu) and activity in brain regions overlapping with the DMN.MethodsIn 18 nicotine-dependent individuals, we assessed the relationship between DMN activation to smoking relative to neutral cues using functional magnetic resonance imaging and dACC Glu as measured by magnetic resonance spectroscopy. This association also was tested in a replication sample of 14 nicotine-dependent participants.ResultsNot only was the DMN significantly less suppressed during smoking cue exposure, but also there was a positive association between DMN reactivity to smoking relative to neutral cues and dACC Glu (r = 0.56, p < 0.02). This finding was confirmed in the independent replication cohort (r = 0.64, p < 0.02).ConclusionsThe current findings confirm that the DMN is less suppressed when smokers view smoking relative to neutral cues, suggesting that smoking cues engage self-relevant processing. Furthermore, these results indicate that dACC Glu is associated with enhanced DMN engagement when nicotine-dependent individuals are exposed to self-relevant smoking cues.