Millions of boys could be at increased risk of Alzheimer's disease and other mental illnesses in later life through playing action video games such as Call of Dutyor Assassin's Creed, according to new research.
Scientists say players navigate the screen using a key area of the brain called the caudate nucleus, which leads to loss of grey matter in the hippocampus.
Previous studies have shown reduced volume in the hippocampus, which controls memory, learning and emotion, is associated with neurological and psychological disorders including dementia and depression.
The Canadian team said if action gamers have less grey matter, as people who rely on the caudate nucleus normally do, then they may be more prone to mental illness.
In the study, published in Proceedings of the Royal Society B, they tested 26 players and 33 non players who wore skull caps recording their brainwaves and eye movements as they negotiated a virtual maze decorated with trees and mountains from which they had to retrieve objects.
It found the players were twice as likely to use their caudate nucleus (80.76%) during navigation rather than the non-gamers (42.42%) who tended to rely on the brain's spatial memory system, the hippocampus.
The caudate nucleus is the brain's reward system and has also been linked with drug and alcohol addiction.
Dr Gregory West, of the University of Montreal, said: "For more than a decade now, research has demonstrated action video game players display more efficient visual attention abilities. Our current study again confirms this notion.
CT scan of a brain axial section showing atrophy due to Alzheimer's disease in a 84 year old male patient
"We, however, also found action video game players use navigation strategies that rely on the caudate nucleus to a much greater degree than non video game players.
"Past research has shown people who rely on caudate nucleus dependent strategies have lower grey matter and functional brain activity in the hippocampus.
"This means people who play a lot of action video games could have reduced hippocampal integrity, which is associated with increased risk for neurological disorders such as Alzheimer's disease."
The researchers said people across the world now spend three billion hours a week playing video games, and it is estimated the average young person will now have clocked up almost 10,000 hours by the time they are 21. But the effect of intense gaming on the brain are just beginning to emerge.
As past research has promoted video games as having positive effects on attention, it is important for future research to confirm gaming does not harm the hippocampus. • Has Stanford University found a cure for Alzheimer's disease?
The researchers said brain scans will be required to further underline the findings and should investigate the direct effects of specific action video games on the caudate nucleus and the hippocampus.
Previous research has also shown brains of people who regularly play computer games differ from those of infrequent gamers.
A study in teenagers showed the "reward hub", which is involved in addiction, was larger in regular players.
Brain scans showed a larger ventral striatum, which is the hub of the brain's reward system, in regular gamers. Playing computer games has been linked to a range of effects from addiction to improved reasoning.