It's common knowledge that a drink or two can lower inhibitions and result in people becoming aggressive and violent. Researchers from the University of New South Wales in Australia are asking why, using MRI scans to trace which part of the brain controls aggression.

The study involved 50 otherwise healthy male participants, who were given either a low dose of vodka or two glasses of a non-alcoholic placebo drink. Then using the Taylor Aggression Paradigm, a competitive reaction time task that has been used for the past 50 years to test aggression, the researchers used MRI scanner to identify which areas of the brain lit up when they behaved aggressively.

They found that participants who drank alcohol showed a temporary decrease in activity in the prefrontal cortex, a part of the brain which is believed to regulate aggressive behavior.

"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," says Thomas Denson, lead author of the study. "These regions may support different behaviors, such as peace versus aggression, depending on whether a person is sober or intoxicated."

The alcohol was also found to decrease reward activation in the brain, reducing activity in the ventral striatum and the caudate, while the hippocampus, which is associated with memory, showed an increase in activity.

The research builds on existing theories on alcohol-related aggression, including another study that used neural imaging to show changes in the prefrontal cortex and the ventral striatum.

"We encourage future, larger-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," says Denson.

The team's study was published in Cognitive, Affective & Behavioral Neuroscience.

Source: University of New South Wales