Altered inter-hemispheric and intra-hemispheric functional connectivity dynamics in male cigarette smokers

Previous study has overlooked the heterogeneity between hemispheres and the knowledge of brain temporal dynamics in tobacco use disorder (TUD) individuals was limited. Traditional whole-brain based approaches hampered the exploration of dynamic functional connectivity at the hemisphere level.

We recruited 110 male subjects, including 70 smokers (32 high dependence smokers, 38 low dependence smokers) and 40 non-smokers, then obtained their rs-fMRI data and smoking clinical scales. The functional connections of whole-brain were decomposed into inter-hemispheric and intra-hemispheric connections. Meanwhile, sliding window method was used to evaluate inter- and intra-hemispheric dynamic functional connectivity density (dFCD) variability. Finally, correlation analyses were conducted to explore the relationship between dFCD variability and clinical scales.

We found shared dFCD variability in visual cortex of bilateral hemispheres among all smokers. Compared to low dependence smokers, high dependence smokers showed higher inter-hemispheric dFCD variability in left insula, and lower intra-hemispheric dFCD variability in right inferior frontal gyrus (IFG) and right inferior parietal lobule (IPL). Moreover, intra-hemispheric dFCD variability of right IPL in high dependence smokers was associated with physical dependence rather than psychosocial factors.

This study revealed shared inter/intra-hemispheric dFCD variability of visual cortex, and different connection patterns of frontoparietal control network and insula at hemisphere level in smokers. These findings supply novel insights into brain functional aberrance in TUD from a dynamic perspective, and suggest hemispheric specialization and aberrant inter-hemispheric communication in TUD.