Jayne Gackenbach, a professor of psychology and sociology at Grant MacEwan College, Canada has completed research which claims that video games alter the way the brain works. Gackenbach has been researching dreams for almost 30 years, and in 1997 she polled a group of her students on the effects gaming had on their dreams, with inconclusive results.
In 2004 she repeated the poll and found that frequent video game players have more "lucid dreams" (in which the dreamer is aware that they are dreaming) than non-gamers. Often, the dreamer can even manipulate the action or observe it in third-person, much like a video game.
"On an intuitive level, it makes sense," said Gackenbach. "If you're spending a lot of time in a changeable virtual environment, it acts as a sort of practice for another virtual reality, dreams."
I am waiting for the first Massive Online Dream Dungeon.
More here (pdf).
Image taken from a playstation campaign.