Overnight Abstinence Is Associated With Smaller Secondary Somatosensory Cortical Volumes and Higher Somatosensory-Motor Cortical Functional Connectivity in Cigarette Smokers

Abstract

Introduction: Abstinence symptoms present challenges to successful cessation of cigarette smoking. Chronic exposure to nicotine and long-term nicotine abstinence are associated with alterations in cortical and subcortical gray matter volumes (GMVs).

Aims and methods: We aimed at examining changes in regional GMVs following overnight abstinence and how these regional functions relate to abstinence symptoms. Here, in a sample of 31 regular smokers scanned both in a satiety state and after overnight abstinence, we employed voxel-wise morphometry and resting-state functional connectivity (rsFC) to investigate these issues. We processed imaging data with published routines and evaluated the results with a corrected threshold.

Results: Smokers showed smaller GMVs of the left ventral hippocampus and right secondary somatosensory cortex (SII) after overnight abstinence as compared to satiety. The GMV alterations in right SII were positively correlated with changes in withdrawal symptom severity between states. Furthermore, right SII rsFC with the precentral gyrus was stronger in abstinence as compared to satiety. The inter-regional rsFC was positively correlated with motor impulsivity and withdrawal symptom severity during abstinence and negatively with craving to smoke during satiety.

Conclusions: These findings highlight for the first time the effects of overnight abstinence on cerebral volumetrics and changes in functional connectivity of a higher-order sensory cortex. These changes may dispose smokers to impulsive behaviors and aggravate the urge to smoke at the earliest stage of withdrawal from nicotine.

Implications: Overnight abstinence leads to changes in gray matter volumes and functional connectivity of the second somatosensory cortex in cigarette smokers. Higher somatosensory and motor cortical connectivity in abstinence is significantly correlated with trait motor impulsivity and withdrawal symptom severity. The findings add to the literature of neural markers of nicotine addiction.

Figure 1.

(A) Whole-brain analysis identified the left ventral HP and right SII showing smaller GMVs in abstinence versus satiety. The inset shows the coronal section of the two clusters at y = −15. Color bar shows T value and Cohen’s d for the clusters. (B) Connected-line plots show the GMVs of left ventral HP and right SII of each participant in abstinence versus satiety: 25 and 27 of the 31 subjects showed lower GMVs in abstinence versus satiety for the left ventral HP and right SII, respectively. GMV, gray matter volume; HP, hippocampus; SII, secondary somatosensory cortex. ***p < .001.

Figure 2.

Right precentral gyrus (PrCG) shows stronger rsFC with the right secondary somatosensory cortex (SII) in abstinence versus satiety (center). Color bar shows T value and Cohen’s d. Correlations between right SII-PrCG rsFC and (A) BIS-11 motor subscore, (B) withdrawal symptoms, (C) craving to smoke, and (D) state anxiety in the state of abstinence and satiety. Crosses represent individual data points and dashed lines represent 95% confidence intervals of the mean regressions (solid lines). *p < .05.