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 study released on Tuesday 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 first-person shooter game called "Medal of Honor: 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 Dr. Vincent Mathews, a professor of radiology at Indiana University School of Medicine in Indianapolis and the study’s author.

After playing the games, the children completed tasks requiring concentration and processing of emotional stimuli while their brain activity was scanned. Alterations in brain function reflecting changes in blood flow appeared as brightly colored areas on the magnetic resonance images.

"What we showed is there is an increase in emotional arousal. The fight or flight response is activated after playing a violent video game," Mathews said.

The findings were presented at a meeting of the Radiological Society of North America.

The $13 billion 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.

Video games with a T-rating (for Teen) are considered suitable for ages 13 and older. They may contain violent content, strong language or suggestive themes.

Numerous behavioral and cognitive studies have linked exposure to violent media and aggressive behavior. Now, researchers are using advanced imaging technology to scan the brain for clues to whether violent video games cause increases in aggression.

Mathews said he hopes to conduct additional studies on the long-term effects on brain function of exposure to violent video games.