Gray matter volume correlates of global positive alcohol expectancy in non-dependent adult drinkers

Abstract

Alcohol use and misuse is known to involve structural brain changes. Numerous imaging studies have examined changes in gray matter (GM) volumes in dependent drinkers, but there is little information on whether non-dependent drinking is associated with structural changes and whether these changes are related to psychological factors-such as alcohol expectancy-that influence drinking behavior. We used voxel-based morphometry (VBM) to examine whether the global positive scale of alcohol expectancy, as measured by the Alcohol Expectancy Questionnaire-3, is associated with specific structural markers and whether such markers are associated with drinking behavior in 113 adult non-dependent drinkers (66 women). Alcohol expectancy is positively correlated with GM volume of left precentral gyrus (PCG) in men and women combined and bilateral superior frontal gyri (SFG) in women, and negatively correlated with GM volume of the right ventral putamen in men. Furthermore, mediation analyses showed that the GM volume of PCG mediate the correlation of alcohol expectancy and the average number of drinks consumed per occasion and monthly total number of drinks in the past year. When recent drinking was directly accounted for in multiple regressions, GM volume of bilateral dorsolateral prefrontal cortices correlated positively with alcohol expectancy in the combined sample. To our knowledge, these results are the first to identify the structural brain correlates of alcohol expectancy and its mediation of drinking behaviors. These findings suggest that more studies are needed to investigate increased GM volume in the frontal cortices as a neural correlate of alcohol expectancy.

Keywords: Cerebral morphometry; frontal cortex; gender difference; positive alcohol expectancy; prefrontal cortex; social drinkers.

Figure 1

Voxel based morphometry: multiple regressions against alcohol expectancy. The clusters show regions with GM volume correlated with alcohol expectancy, p<0.001, uncorrected. (A) men and women combined (n=113): precentral gyrus; (B) women (n=66): superior frontal gyrus; (C) men (n=47): ventral putamen. (D) When alcohol consumption is accounted for as a covariate, the GM volume of bilateral dorsolateral prefrontal cortices (DLPFC) correlated positively with alcohol expectancy in men and women combined (n=113), p<0.001, uncorrected. Color bars represent voxel T value; warm color: positive correlation with AEQ; cool color: negative correlation with AEQ. The numbers at the bottom are z coordinates of axial sections.

Figure 2

Correlation of GM volume of regions of interest (ROIs) with alcohol expectancy plotted for men and women separately: (A) left precentral gyrus; (B) bilateral superior frontal gyri; and (C) right ventral putamen. Inset shows results of differences in the regression slope between men and women for each of the ROIs.

Figure 3

Single-level mediation analysis of alcohol expectancy (AE), drinking variables, and GM volumes. Dashed arrows indicate the lack of a significant connectivity at p<0.05, Bonferroni corrected (p=0.05/4=0.0125). The mark “*” indicates significant mediation at p<0.05, corrected.