Drunken bravado has biological roots, according to a brain-scan study that finds that alcohol inhibits the ability to feel fear, HealthDay News reported April 30.

"You're less likely to feel afraid, and you're also less likely to run away or to avoid conflict," said study co-author Daniel Hommer of the National Institute on Alcoholism and Alcohol Abuse.

Researchers conducted brain scans on a group of 12 social drinkers with an average age of 26 who were given either alcohol or a saline solution intravenously. The subjects were then shown images designed to evoke a fear response while their brain patterns were monitored via functional MRI scans.

The study showed that alcohol increased activity in the reward centers of the brain but depressed activity in areas involved in fear response.

The findings were published in the April 30, 2008 issue of the Journal of Neuroscience.