Beijing -- Teens who play violent video games show increased activity in areas of the brain linked to emotional arousal and decreased responses in regions that govern self-control, a recent study found.

The study used functional magnetic resonance imaging to record tiny metabolic changes in brain activity in 44 adolescents who were asked to perform a series of tasks after playing either a violent or nonviolent video game for 30 minutes.

The children, with no history of behavior problems, ranged in age from 13 to 17. Half played a T-rated (for Teen) first-person shooter game called Medal of Honour: Frontline, involving military combat, while the other group played a nonviolent game called Need for Speed: Underground.

Those who played the violent video game showed more activation in the amygdala, which is involved in emotional arousal, and less activation in the prefrontal portions of the brain associated with control, focus and concentration than the teens who played the nonviolent game.

"Our study suggests that playing a certain type of violent video game may have different short-term effects on brain function than playing a nonviolent, but exciting, game," said Vincent Mathews, a professor of radiology at Indiana University School of Medicine in Indianapolis and the study's author.

The findings were presented at a meeting of the Radiological Society of North America. The 13 billion dollars U.S. video game industry, with revenue rivaling Hollywood box office sales, is at the center of a cultural battle over violent content.

Lawmakers' various attempts to ban the sale of violent video games to children have been blocked by courts in Louisiana, Illinois, California. Michigan and Minnesota.