FRIDAY, Dec. 5, 2008 (HealthDay News) -- College students who think all-night study sessions will help them remember facts might want to get some sleep instead. And not just because they'll be more rested when it's time for the test.
That's the message from a new study that finds that as you sleep, the mind consolidates the things you learn during the day.
Study participants who learned how to play a video game in the morning or evening did a better job the next day after a night's rest, apparently because their brains were actively absorbing what they'd learned as they slept.
The finding shows "that sleep is not just a passive state when no information is coming in," said study co-author Howard Nusbaum, a professor of psychology at the University of Chicago. "It could be the case that people who are pulling all-nighters are not doing themselves a favor."
For the study, the researchers recruited 200 college students, most of them women. Most of them weren't very familiar with playing video games, so they were taught to play the games "Quake III" and "Unreal Tournament" -- so-called "first-person shooter" games that require players to attack enemies.
Some of the participants learned how to play the games in the morning, while others learned in the evening. The researchers then tested the subjects on the video games 12 hours later and 24 hours later.
Those who took part in the morning training sessions showed an average eight-percentage-point improvement in their performance immediately after training. They performed more poorly -- scoring four percentage points better -- 12 hours later. But they scored 10 percentage points better the next morning.
"If we train you in the morning and come back at the end of the day, you forget some of what you learned," Nusbaum said. "But if you sleep after that, it restores some of what you learned."
The students who took part in the evening training sessions performed better the next morning after sleeping, than they did after being trained.
The study findings were published in the current issue of the journal Learning & Memory.
Nusbaum believes that people encounter "lots of interference" during the course of a day, and "you forget some of what you've learned." But researchers don't yet know what causes the interference.
The role that dreams play in the learning process -- if any -- isn't clear either. But some dreams could serve as a kind of practice for the brain, Nusbaum said.
"If you play a video game a lot, and you're playing in your dreams, maybe that could help you learn," he said.
Jerry Siegel, professor at the Center for Sleep Research at the University of Calfornia, Los Angeles, said going without sleep hurts performance, but he's not convinced that sleep itself actively contributes to learning.
"If you take a break for a few hours, it can easily be shown that learning did occur, because performance is better at the start of a new learning session than it was at the end of the initial session," he said. "No sleep needs to occur for this to happen."
Still, Siegel, who reviewed the new study, suggested that sleep before learning a skill is crucial.
"For long-term retention, it is more important to be well rested and therefore attentive when you are doing the learning than afterwards," he said. "It is even better if you don't have to choose and get your natural amounts of sleep every day."
Get basic information about sleep from the University of Washington.