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.
