Saturday, January 22, 2022

Brain Activity Helps Explain Response to Alcohol

People who need to drink relatively high amounts of alcohol before feeling its effects, a genetically influenced risk factor for future heavy drinking and alcohol problems, may have differences in brain connectivity that impair their ability to interpret facial expressions and recognize their own intoxication, a new study suggests. The paper, in Alcoholism: Clinical & Experimental Research, is believed to be the first to demonstrate differences in brain connectivity between people with low and high responses to alcohol. Varying levels of responses to alcohol — for example, how many drinks a person consumes before feeling intoxicated — are known to be related to neurobiological processing. Low responders, who drink more alcohol before feeling affected by it, are at greater risk of alcohol use disorder (AUD) than high responders, who feel the effects of fewer drinks. 

Scientists using functional magnetic resonance imaging (fMRI) are exploring the possibility that low responders are less able to recognize certain modest sensory inputs because of atypical brain connectivity. Previous studies found that low responders are likely to require greater effort than high responders to identify facial emotions, a task that is key to social and emotional functioning. For the new study, researchers at the University of California San Diego showed pictures of happy, angry, and fearful faces to study participants undergoing brain scans. They examined connectivity between the amygdala, a structure involved in processing emotions and reward, and other brain regions, and whether differences between low and high responders were associated with problematic drinking later.

The study involved 108 college students aged 18–25. The students had taken an alcohol challenge and been identified as having either a low or high response to alcohol; none had developed an AUD before testing. They were organized into 54 pairs of low and high responders matched by sex, demographics, and substance use. Each participant underwent two fMRI sessions during which they observed pictures of faces, one after consuming alcohol, the other after a placebo beverage. The investigators measured the students’ accuracy at identifying facial expressions, compared amygdala activity, and used statistical analysis to look for associations between alcohol responses and problematic drinking five years later.

The results showed differences in functional connectivity between the brains of low and high responders during the emotional processing task. Low-response participants observing pictures of angry faces, after both alcoholic and placebo drinks, had diminished amygdala connectivity with the cortical regions of the brain compared to their high-response peers. In addition, low responders’ functional connectivity when viewing angry and happy faces declined after drinking alcohol, while high responders’ connectivity increased. Fearful faces did not reveal similarly divergent responses, suggesting that distinct emotional experiences trigger specific biological processes. Two regional brain differences observed in low responders after the placebo beverage were associated with increased alcohol problems five years later.

The findings suggest that people with low responses to alcohol may have aberrant functional connectivity in certain brain circuits. These differences in their neurobiological processing could impair their performance in certain cognitive tasks, such as interpretating facial expressions, as well as their ability to recognize their own intoxication — the rewarding aspects of alcohol — in social situations. The investigators cautioned that the study results may not apply to everyone and called for further research on fMRI findings as predictors of future drinking problems.

Source/Credit: Research Society on Alcoholism