Some studies have shown a connection between gaming and emotional arousal, although there's no evidence that this heightened emotional state leads to physical violence.
In 2006, a small study by Indiana University found that teenagers who played violent video games showed higher levels of emotional arousal, but less activity in the parts of the brain associated with the ability to plan, control and direct thoughts and behavior.
The study assigned 44 adolescents to play either a violent or nonviolent but "equally fun and exciting" video game for half an hour. Researchers measured their brain function immediately after playing. The group that played the nonviolent game showed more activity in the prefrontal parts of the brain, which are involved in inhibition, concentration and self-control. They also showed less activity in the area involved in emotional arousal.
But if those changes have any impact on real-world behavior, researchers haven't yet detected it.