Individuals with a low response level to alcohol display differences in brain activity. This brain difference may contribute to an inability to recognize modest levels of alcohol intoxication, says a study by researchers at the University of California, San Diego School of Medicine.
These findings could provide a marker capable of identifying individuals who are at risk for developing an alcohol-use disorder before it starts.
For the study, researchers used functional magnetic resonance imaging (fMRI) to view brain activation in young men and women in San Diego, ages 18 to 25, with both low and high level of response (LR) to alcohol.
“We found significant differences in brain activation between individuals with high and low levels of response to alcohol while performing a cognitive task, possibly reflecting difference in the amount of brain activity used to deal with a cognitive challenge,” said Dr. Marc A. Schuckit, Distinguished Professor of Psychiatry at UC San Diego and leader of the study.
A low response level to alcohol is considered a genetically influenced characteristic, or phenotype, that carries a greater risk for alcoholism. This study looked into the physiological factors of a low and high LR, finding notable differences in brain activity during a cognitive task, possibly revealing differences in the amount of brain activity used to deal with a cognitive challenge.
“While some genes that contribute to LR have been provisionally identified, the mechanism through which the low LR operates in the brain has not been extensively studied,” said Schuckit. “This report confirms prior reports from our group that used a different cognitive task to show that people with a low LR process information differently from those with a high LR even when tested with placebo.”
“The differences between LR groups after placebo and alcohol across different cognitive tasks may help explain why low LR subjects might have more problems recognizing the effects of moderate doses of alcohol. If you aren’t able to recognize the effects of lower doses of alcohol, you are more likely to drink heavy amounts per occasion, which both directly and indirectly increases your risk for alcohol problems,” said Schuckit.
For the study, 98 volunteers (52 females, 46 males) who were young, healthy drinkers and non-alcohol dependent were previously identified through testing as clearly having low or high LRs to alcohol. The participants in the two LR groups were matched to be similar on recent drinking histories, age, gender, race and histories of smoking and use of illicit drugs.
All volunteers were evaluated during two fMRI sessions while they performed a cognitive task. The two groups were given either a placebo or an amount of alcohol roughly equal to three standard drinks, in random order. Treated subjects developed identical blood alcohol levels during the sessions.
After placebo, the low LR subjects seemed to exert more cognitive effort in performing the task than those with high LRs. But after alcohol, low LR subjects appeared to carry out the task with less effort than they had after placebo. In contrast, high LR subjects had to work harder to do the task after alcohol than after placebo.
“When the low LR people drink modest amounts of alcohol, they may not perceive much change in how their brain is working,” said Schuckit.
“If a modest dose of alcohol produces a situation where you don’t have to exert as much effort to think about how a challenging task that needs to be done — as might be true for low LR subjects — perhaps drinking is a bit more rewarding for you, compared to people who find that modest alcohol doses actually impairs their thinking, as is seen for high LR subjects.”
“The real issue for clinicians is that the low LR is an important, genetically influenced risk factor for later alcohol problems,” Schuckit added. “These results can also inform researchers interested in how the low LR might actually work to affect how intoxicated a person might feel.”
The study will be published in the January 2012 issue of Alcoholism: Clinical & Experimental Research.
Source: University of California