Why do people tend to get aggressive after a drink or two? It is because certain areas in the brain that temper aggression shuts off, researchers say.

In the study, the researchers noted changes in the working of the prefrontal cortex -- the brain area involved in tempering a person's levels of aggression, cognitive behaviour and decision making -- in participants just after two drinks. While being provoked was found to have no influence on participants' neural responses, but when behaving aggressively, there was a dip in activity in the prefrontal cortex of those who had consumed alcoholic drinks.

This dampening effect was also seen in the areas of the brain that are involved with rewards. Also, heightened activity was noted in the hippocampus, the part of the brain associated with memories. "Although there was an overall dampening effect of alcohol on the prefrontal cortex, even at a low dose of alcohol, we observed a significant positive relationship between dorsomedial and dorsolateral prefrontal cortex activity and alcohol-related aggression," said Thomas Denson, Associate professor at the University of New South Wales in Autralia.

"These regions may support different behaviours, such as peace versus aggression, depending on whether a person is sober or intoxicated," Denson added. The findings, published in the journal Cognitive, Affective, and Behavioural Neuroscience, may help reduce alcohol-related harm. The team recruited a small group of young men, who were either given two drinks containing vodka, or placebo drinks without any alcohol and then underwent a functional magnetic resonance imaging (fMRI) scan.

There is a need for "large-scale investigations into the neural underpinnings of alcohol-related aggression with stronger doses and clinical samples. Doing so could eventually substantially reduce alcohol-related harm", Denson said.