For quite some time, researchers believed that learning took place only during the fifth, or REM, stage of sleep; in fact, when a task was studied that showed that REM sleep wasn’t involved in its comprehension, some scientists continued to believe that sleep wasn’t involved in learning at all. Now, however, not only is it certain that sleep is involved in learning, but as we continue to test tasks we’re finding that every stage of sleep has an important part in making it happen.
In general, it appears that NREM, or non-REM, sleep—the first four stages of sleep—facilitates declarative, or facts-and-figures, learning. REM sleep, the last stage of the sleep cycle, seems to enable the consolidation of procedural, or more complex, learning. Enhanced sleep-dependent performance, in fact, has been associated with both slow wave sleep in the early part of the night and REM sleep in the later part of the night. Some researchers believe, though, that both types of sleep affect learning in a complementary and sequential way. Studies of birds have shown that both slow wave sleep, the kind found in Stages 3 and 4, and REM sleep play complementary roles in their memory consolidation.
But whether or not the different kinds of learning take place in one stage of sleep or across several stages, we need a full night of uninterrupted sleep, cycling through all the stages to the maximum extent, to give our brain the time it needs to lay down, consolidate, and enhance both types of memory. Only in this way can we learn much of anything—studies show that less than six hours of sleep the night following information intake blocks the positive effect of sleep on learning.
But one night of great sleep is not enough. To really cement the learning that’s taking place, the brain needs three consecutive nights of adequate, regular rest. But the first night is key—if you don’t get enough sleep then, the information you took in gets wiped out and isn’t necessarily recoverable on the second and third nights. In your teen’s case, if she starts reading a book the day before a test on it and stays up till 2:00 a.m. to finish it, all the information that was taken in won’t be there come test time if the bus arrives for pickup at 7:15. In simple terms, all-nighters don’t work; sleep does. As a good friend always said in college when faced with a big exam the next day, better