By Mike Magee, MD Over the years of child rearing, my wife and I (thankfully) agreed on most things. But one area where she and I diverged was on bedtime. For me, sleeping was no big deal. For her, an early childhood educator, bed times were ironclad and serious business. Recent research on the purpose and value of sleep would suggest that, once again, she was right.1 It seems that sleep is vital to both memory and learning – and it appears America’s kids aren’t getting enough of it. More on that later. Harvard sleep expert Allan Hobson says, “…for years, [researchers] saw sleep as nothing but an annihilation of consciousness. Now we know different.”2 What researchers know has been relatively recent and slow in development. Modern sleep theory dates back only to 1952 when a University of Chicago grad student, Eugene Aserinsky, decided to hook up his 8-year-old son to a bunch of brain electrodes while he slept just to see what was going on inside his brain. To alert him when the boy was awake and opened his eyes, he also wired the eyelids. What he discovered, and subsequently published with his faculty adviser in 1953, was named rapid eye movement -- or REM -- sleep.3 Years later, this odd unconscious state, somewhere between light and deep sleep, was described by modern day sleep researcher Ross Levin, now armed with sophisticated imaging equipment, as “neurochemically…like the Fourth of July…incredibly active, much more so then when you’re awake.”2 Researchers now split sleep into four parts: light sleep, true sleep, deep sleep and REM sleep.4 When we first drop off to sleep, it is light. We’re literally half awake typically for 5 to 15 minutes. Our eyes are closed but we are easily awakened. But between 10 and 30 minutes of lying down, most move into true sleep. Breathing slows down and is regular. Heart rates and body temperatures drop. Over the next hour we sink into a deep sleep as our brain waves slow and our heart rate drops to its lowest level. While we may appear inactive, inside, there’s work to be done. Hormones are secreting, and muscles, bones, and tissues regenerating. An hour or two into the night’s rest, most walk back up the ladder quickly through true and light sleep for a run of REM sleep. At this point our brain is most active. Our eyes dart around under our closed lids. Breathing and blood pressure varies, but our muscles are paralyzed. Our dreams sometimes are wild, but we cannot act on them thankfully because we cannot move. Over the course of a typical light hour sleep, we repeat the cycle some four times. In total we spent about a quarter of the time in a mixture of light or REM sleep, about half the time in true sleep, and a quarter of the time in deep sleep.2 These different types of sleep occur at different times and are now believed to serve different purposes.5 For example we go in and out of REM sleep four or so times a night and with each episode, it lasts longer, with the longest stretch typically lasting close to an hour near the end of the sleep. Thus, if you cut off sleep early by rising an hour or two before normal, you can loose more than 50 percent of your REM sleep for that night. Researchers in 1994 discovered that REM sleep is critical to remembering things you learned the prior day.6 During REM sleep it appears that the brain separates, bundles and stores facts away in an organized fashion so that they ca be easily analyzed and retrieved. REM learning is felt to be especially critical for position recognition like learning grammar or playing games that require strategic moves and forward thinking.6 In addition, through dreams and other processes, during REM sleep we appear to discard useless facts.7 In contrast, deep sleep, which generally occurs in the first third of the evening, is felt to be critical for recall of memorized facts. Real sleep, that middle level of unconsciousness, which is spread more evenly throughout the night but still weighted more heavily toward the early morning hours, is believed to be critical in learning all sorts of motor tasks -- from managing a musical instrument to executing the perfect jump shot or swimming turn.2 There is clearly still a great deal to learn about sleep. But here’s what we know for sure. 1. Sleep is an active rather than passive event tied to memory and learning. 2. Not all sleep is the same. There are different types of sleep, which appear to serve different functions in the acquisition of knowledge. 3. Getting enough of the right types of sleep is essential. All-nighters rob the individual of time to organize and categorize what was just memorized. The risk? Losing all of that hard work. So it turns out my wife was right again. Recent reports say that 15 million school age children in America are suffering from inadequate sleep. Studies also show these children perform less well in tests, have less recall and responsiveness, have more depressive feelings, and perform less well in coordination and motor activities.8 Bottom line: Kids need a good nights sleep to learn. And it’s a parent’s job to make sure they get it. References 1. Science Daily. “Evidence that learning is consolidated during sleep.” 1 November 2004. 2. Carey B. An active, purposeful machine that comes out at night to play. New York Times. 23 October 2007. F1. 3. Aserinsky E., Klutman N. Regularly occurring periods of eye motility, and concomitant phenomena during sleep. Science. 1953; 118:273-274. 4. Lamberg L. Scientists never dreamed finding would shape a half century of sleep research. JAMA 2003:200;2652-2654. 5. Cromie WJ. Research links sleep, dreams and learning. Harvard University Gazette Research. 8 February 1996. 6. Karri A et al. Dependence on REM sleep of overnight improvement of a perceptual skill. Science. 29 July 1994 (265):5172:679-682. 7. Angier N. In the dreamscape of nightmares, clues to why we dream at all. New York Times. 23 October 2007. F1. 8. Carskadon, M. First National Sleep Conference. March 29-30. Explores Sleep’s role in Public Health NIH News. 25 March 2004. | 
