Functional changes in the brains of social drinkers

Abstract

The aim of this study was to investigate the consequences of chronic non-pathological drinking, i.e., social drinking, on brain functioning. While ERPs were recorded, social drinking participants were assessed on cognitive tasks, which were chosen because normal functioning in these tasks allegedly depends on undamaged frontal lobes.

Verb generation task

Two studies were described. Study 1 involved two groups of students, a moderate social drinkers group and a heavy social drinkers group. Study 2 involved three older groups of social drinkers (light, moderate and, heavy) and an excessive drinkers group (mean age approximately 50 years). Interaction effects between group and verb generation were found at one mid frontal scalp location and at two right frontal scalp locations. An expected task effect, larger amplitudes for generating than for reading at an early latency at Fz, was found in both groups in study 1, but only for the light social drinkers in study 2. The moderate, heavy and excessive drinkers in study 2 did not show this task effect. Excessive drinkers also made more retrieval errors than the heavy social drinkers and differed at right frontal (F4) ERP components from the heavy social drinkers. A third interaction effect was found at the right frontal lead F6. At F6 higher amplitude was found for generating than for reading for the moderate drinkers of study 1 and the light drinkers of study 2.

Wisconsin card-sorting task

In the Wisconsin card-sorting task the N1 ERP component in response to the feedback stimuli differed between groups. The light social drinkers showed a trend towards more early negativity (N1) on early trials than on late trials; this effect was significant for the moderate drinkers, but absent in the heavy and excessive groups.

Other tasks In neither the continuous performance task, the visual attention task, nor the auditory odd-ball task, differences between social drinking groups were found on the various ERP components. According to the DSM-IV criteria, a subgroup of five participants in the excessive drinking group scored for alcohol dependence. Contrasting this subgroup of alcohol dependent participants with light social drinkers showed significantly smaller frontal Go P3 in the continuous performance task, and a trend towards smaller parietal P3 to attended stimuli in the visual attention task. No effects were found with respect to the auditory odd-ball task.Conclusion This study provides new insights in the effects of long-term alcohol use. We propose that the effects of alcohol use begin with very mild cognitive effects in young social drinkers, which are found at the right frontal cortex; with progressing age and alcohol use the effects become visible on more ERP components that expand to mid-frontal locations. It seems that all these effects in social drinkers are only found when the brain is challenged with more demanding or complex tasks. When participants become dependent on alcohol, also less complex and less demanding attention and inhibition tasks show effects that, in case of the visual attention task, also become more widespread, involving also parietal scalp locations.