Researchers are discovering surprising differences between the brains of adults and those of teenagers -- differences that have begun to explain at least some of the differences in the way these two groups think. One aspect of the teenage way of life, however, may affect the moods, actions, and potential of young people just as much if not more than brain anatomy: lack of sleep.

Many teenagers today juggle so many activities that there is just not enough time in the day to get everything done -- unless they give something up. Very often that "something" is sleep. With most high schools in the United States starting at around 7:20 a.m., and with many teens going to bed between 11 p.m. and midnight, sleep researchers worry that teenagers across the country are getting far too little sleep. This trend of sleep deprivation among young people, they say, is having a dramatic impact on many aspects of teenagers' lives, including their ability to learn.

Studies conducted at Harvard Medical School and Trent University in Canada have found strong evidence to support the sleep/learning connection. In these experiments students were put through a battery of cognitive tests. Afterwards they were allowed to sleep various lengths of time, and then were re-tested on the same material to determine how sleep affected their ability to learn. The results showed that after the students went to sleep, their brains "practiced" what they had learned during the day. While parents always knew intuitively that sleep helped learning, few people recognized that learning actually continues to take place while a person is asleep. This means that sleep after a lesson is as important as getting a good night's rest immediately prior to a test or exam.

According to researchers, the brain practices what it has learned during two particular phases of sleep. During the first part of the night, the levels of several brain chemicals fall sharply. Facilitated by this chemical change, information flows out of the hippocampus and into the surrounding cerebral cortex. Then, according to one neuroscientist, during a phase of sleep called slow-wave sleep, the brain distributes this new information into the appropriate networks. Inside the brain, proteins strengthen the connections between the nerve cells responsible for transmitting the new information. Later, during a phase of sleep called REM (for Rapid Eye Movement), the brain replays the lessons from the previous day and solidifies the newly made connections.

Unfortunately, practicing good sleep habits is particularly difficult for teenagers. Not only do their own natural sleep rhythms fight against going to sleep early, but many teens have no control over what time they must wake up. Teens can do something to try to reset their internal body clocks, however. Sleep experts say dimming the lights at night and getting lots of daylight in the morning can help. Having a routine bedtime of no later than 10 p.m., sleeping in a cool environment, and turning off the stereo, TV, and computer when it is time for bed can also help teens reset their body clocks.