New brain imaging research published this week shows that, after consuming alcohol, social drinkers had decreased sensitivity in brain regions involved in detecting threats, and increased activity in brain regions involved in reward.
The study, in the April 30 issue of The Journal of Neuroscience, is the first human brain imaging study of alcohol's effect on the response of neuronal circuits to threatening stimuli.
"The key finding of this study is that after alcohol exposure, threat-detecting brain circuits can't tell the difference between a threatening and non-threatening social stimulus," said Marina Wolf, PhD, at Rosalind Franklin University of Medicine and Science, who was unaffiliated with the study. "At one end of the spectrum, less anxiety might enable us to approach a new person at a party. But at the other end of the spectrum, we may fail to avoid an argument or a fight. By showing that alcohol exerts this effect in normal volunteers by acting on specific brain circuits, these study results make it harder for someone to believe that risky decision-making after alcohol 'doesn't apply to me'," Wolf said.
Working with a dozen healthy participants who drink socially, research fellow Jodi Gilman, working with senior author Daniel Hommer, MD, at the National Institutes on Alcohol Abuse and Alcoholism, used functional magnetic resonance imaging (fMRI) to study activity in emotion-processing brain regions during alcohol exposure. Over two 45-minute periods, the study participants received either alcohol or a saline solution intravenously and were shown images of fearful facial expressions. (Previous studies have shown that expressions of fear signal a threatening situation and activate specific brain regions.)