The way the brain reacts to alcohol has, for the first time, been documented by researchers at the U.S. National Institute on Alcohol Abuse and Alcoholism in Bethesda, Maryland.
Researchers have documented how alcohol affects brain activity. Photo: Cheers! Credit: CUKUFJ/flickr
Researchers Jodi Gilman and Daniel Hommer monitored the brain activity of twelve volunteers who had been injected with alcohol to a level of 0.8 grams of alcohol per 100 millilitres of blood - the legal limit for driving in the UK and the US.
They then compared the volunteers' brain activity using magnetic resonance imaging (MRI) to when they had been sober and found the alcohol had changed the way the brain reacted to images shown them.
The study showed the alcohol-influenced volunteers were unable to identify images of people's faces who exhibited fear, reacting equally to neutral and fearful faces.
Researchers found the the amygdala, which processes emotional reactions in the brain, lit up when fearful faces where shown to the sober volunteers but was less active after alcohol consumption.
"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 at the Rosalind Franklin University of Medicine and Science in Chicago to The Guardian. She was not involved in 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," she said.
"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'."
Gilman and Hommer also showed the reward level of the brain, such as the nucleus accumbens, was stimulated by alcohol, resulting in the time-honoured sense of a pleasurable experience.
The research is published in the Journal of Neuroscience.
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