According to researchers at the University of Illinois at Chicago College of Medicine, previous studies have shown that alcohol suppresses activity in the amygdala. The amygdala is the area of the brain responsible for perceiving social cues, such as facial expressions.
“Because emotional processing involves both the amygdala and areas of the brain located in the prefrontal cortex responsible for cognition and modulation of behavior, we wanted to see if there were any alterations in the functional connectivity or communication between these two brain regions that might underlie alcohol’s effects,” said Dr. K. Luan Phan, a UIC professor of psychiatry.
For the study, the researchers recruited 12 heavy social drinkers — 10 men, two women — with an average age of 23. The subjects’ reported average of 7.8 binge drinking episodes a month — defined as five or more drinks for men and four or more drinks for women — put them at a high risk for developing alcohol dependence, according to the researchers.
The participants were given a beverage containing either a high dose of alcohol (16 percent) or a placebo. They then were asked to match photographs of faces — happy, fearful, angry or neutral — while researchers used functional magnetic resonance imaging (fMRI) to see which areas of the brain were active during the task.
The researchers found that when the participants processed images of angry, fearful and happy faces, those who had the alcohol experienced a reduction in the coupling between the amygdala and the orbitofrontal cortex.
This part of the prefrontal cortex is implicated in processing information in the environment that includes social cues, as well as emotional cues, such as whether another person’s tone is angry or sad. This part of the brain also appears to be important in rational decision-making.
The researchers also noticed that alcohol reduced the reaction in the amygdala to threat signals — the angry or fearful faces.
“This suggests that during acute alcohol intoxication, emotional cues that signal threat are not being processed in the brain normally because the amygdala is not responding as it should be,” Phan said.
It may be that people who drink heavily largely lose the ability to process important contextual information from their environment — especially in relation to other people.
“The amygdala and the prefrontal cortex have a dynamic, interactive relationship,” he continued. “How the amygdala and prefrontal cortex interact enables us to accurately appraise our environment and modulate our reactions to it.”
If these two areas are uncoupled during acute alcohol intoxication, Phan said, then the ability to assess and appropriately respond to the non-verbal message conveyed on the faces of others may be impaired.
“This research gives us a much better idea of what is going on in the brain that leads to some of the maladaptive behaviors we see in alcohol intoxication, including social disinhibition, aggression and social withdrawal,” he concluded.
The study, supported by a Brain Research Foundation Grant, was published in Psychopharmacology.