The brains of teen video gamers look similar to those of addicts, with larger so-called reward centers, a new study suggests.

The reward center, focused around a brain region called the ventral striatum, releases "feel good" chemicals when we do something that helps us survive and reproduce — like eating or mating. Sometimes, as is the case with addiction, these brain regions become overactive in response to non-useful stimuli, like cocaine, alcohol, excessive sex or excessive gambling.

"Our participants did not reach formal criterions of addiction," study researcher Simone Kühn, of Ghent University in Belgium, said in an email to LiveScience. "But indeed especially the finding that they show more activity in a reward region ... might be a mechanism by which behavioral addiction develops."

The researchers can't tell if the gaming caused the brain changes, or if overactive reward centers led to excessive gaming.

Brain on games

The researchers studied 154 14-year-olds. The adolescents filled out questionnaires about their gaming and had undergone functional magnetic resonance imaging, a way to analyze brain structures. Overall, the teens played an average of 12 hours per week — gamers playing under nine hours were considered "infrequent gamers," while those playing more than nine hours were "frequent gamers."

Compared with the infrequent gamers, the frequent gamers had much larger ventral striatums, a reward center in the brain linked to emotional and motivational aspects of behavior. Problems with this area have been correlated to disorders such as schizophrenia, addiction and obsessive-compulsive behaviors.

The teenagers also played a gambling game while the researchers scanned their brain activity. The frequent gamers were faster at making decisions during the game, and their brains showed more activity in the reward circuit when they lost.

"This indicates that losing money is somehow rewarding for frequent gamers," Kühn told LiveScience. "This could be the neural basis of a phenomenon called 'loss chasing,' which is known from pathological gambling. It describes the phenomenon that pathological gamblers keep on playing even when they lose a lot of money."

This larger brain region could mean that the brain of a gamer releases more dopamine (a brain chemical that helps control the brain's reward and pleasure centers) when playing. This has also been seen when Parkinson's disease patients take dopamine, and they sometimes acquire gambling and other addictions as a result.

Which came first?

The researchers can't be sure if the brain changes resulted from the high levels of gaming, or if the high levels of gaming changed the brain. "These findings suggest the importance of striatal volume and activity in shaping preferences of skills for video gaming rather than striatal changes being the consequence of excessive gaming," the researchers write in the Nov. 15 issue of the journal Translational Psychiatry. "Individuals with higher ventral striatum volume might experience video gaming as more rewarding in the first place."

Brain structures have been shown to be malleable — when a physical skill, like juggling, is practiced, motor brain regions enlarge. Changes in brain structure have also been associated with larger social networks, in monkeys and in humans.

An overactive reward system may also be a precondition for excessive gaming, as has been shown in studies published in the journals Cerebral Cortex in 2010 and PLoS ONE in 2011. The studies showed that a larger dorsal striatum and increased striatum activity predicted quicker video-game learning, respectively.

"The burning question that this study does not resolve is whether the structural difference is a change caused by the frequent game play, or whether individual differences in this system naturally dispose some people to more excessive play," Luke Clark, a researcher from the University of Cambridge who wasn't involved in the study, said in a statement. "For teenagers, parents and clinicians to make sense of this finding, we need research monitoring brain structure over time."

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