Do We Learn While We're Asleep?
Studies show that sleep enhances learning, memory, and problem solving
Posted Mar 04, 2012
Although most of us already know that sleep is the time when our bodies and brains replenish, giving us the resources we need to get through the challenges of the day ahead, most of us are quick to move it to the bottom of our swelling to-do lists. But a new Harvard Medical School report, Learning While You Sleep: Dream or Reality?, suggests that the benefits of sleep may extend beyond our daily functioning. It may actually enhance our learning, memory, and creative problem solving—even when our heads are on the pillow.
The Stages of Sleep
To better understand the results of the highlighted studies, here's a quick refresher on how sleep works.
Sleep has two major phases: rapid-eye-movement (REM) and non-rapid-eye-movement (NREM). We begin sleep in the NREM phase, which itself has four stages: Stage 1 (onset), Stage 2 (light sleep), Stages 3 and 4 (deep sleep). After approximately 60 to 90 minutes, most people enter REM sleep, which lasts about 20 to 30 minutes, after which NREM sleep returns and a new sleep cycle begins. During a normal night's sleep, healthy adults experience between four to six consecutive sleep cycles.
Although NREM and REM sleep are both critical for our health and functioning, they are very different in nature. During NREM sleep, the body can move, but eye movements are typically absent. Breathing slows. Heart rate, blood pressure, and blood flow to the brain decreases, and EEGs show a slowing of the brain's activity. In contrast, REM sleep is characterized by physical immobility, rapid eye movement, increased blood flow to the brain, swings in blood pressure, heart rate, and respiratory rate, and spiking on EEGs. Although dreams occur most commonly during REM sleep, they sometimes occur in the early stages of NREM sleep.
Do we learn while we dream?
In a 2010 study, researchers at Harvard discovered that dreaming may reactivate and reorganize recently learned material, improving memory and boosting performance. Subjects were healthy college students with normal sleep patterns who agreed to avoid alcohol, caffeine, and drugs for at least 24 hours prior to the experiment. Each subject spent an hour trying to learn a complex three-dimensional maze-like puzzle. After the training, half of the subjects were allowed to nap for 90 minutes while the others read or relaxed. Afterwards, the subjects returned to the puzzle. Those who reported dreaming about the puzzle during their naps (NREM sleep) were the only ones whose performance substantially improved. The Harvard report notes, "Although the dreams didn't actually depict solutions to the puzzle, the researchers believe they show how the dreaming brain can reorganize and consolidate memories, resulting in better performance on learned tasks."
Do we learn when we nap?
Another Harvard study examined the effects of a 45 minute nap. Subjects were given 30 minutes to work on three tasks: memorizing 60 pairs of unrelated words, solving a maze puzzle, and copying an intricate figure. After being tested on the tasks, half of the subjects were allowed to nap while the other half rested quietly. Later in the afternoon, all subjects repeated the tasks. Researchers found that NREM napping boosted performance for the students whose initial tests demonstrated good learning (although napping did not help the students who scored poorly on their first tests).
But who in today's world has time for a 45 minute nap? Well, it seems that shorter naps may do the trick as well. In 2008, the Journal of Sleep Research published a study that found that even a nap as short as six minutes can improve learning and memory. Subjects were asked to memorize a word list, then tested an hour later. During the break, some of the subjects remained awake, some napped for six minutes, and some took longer naps. Researchers concluded, "In comparing word recall after conditions of no napping (waking), short napping, and long napping, we found superior recall for both nap conditions in contrast to waking as well as for long naps in contrast to short naps. These results demonstrate that even an ultra short period of sleep is sufficient to enhance memory processing. We suggest that the mere onset of sleep may initiate active processes of consolidation which—once triggered—remain effective even if sleep is terminated shortly thereafter."
Is REM even better?
These studies suggest that NREM sleep may improve memory and learning, but other studies suggest that REM sleep is even better. A University of California-San Diego study investigating sleep's impact on creative problem solving gave subjects a series of creative problems. Subjects were tested in the morning, and again in the afternoon, after either a nap with REM sleep, a nap without REM sleep, or a quiet rest period. Researchers manipulated various conditions of prior exposure to elements of the creative problem, and controlled for memory. The lead author of the study, Denise Cai, noted, "Participants grouped by REM sleep, non-REM sleep and quiet rest were indistinguishable on measures of memory. Although the quiet rest and non-REM sleep groups received the same prior exposure to the task, they displayed no improvement on the RAT test. Strikingly, however, the REM sleep group improved by almost 40 percent over their morning performances." This suggests that REM sleep allows the brain to work creatively on problems presented before sleep.
Something to sleep on?
When you combine these benefits with the well-known benefits that a good night's sleep has on our physical health, productivity, performance, and overall mental state, it should serve as a motivator to steal as much sleep as we can. But for many, getting good sleep can present a challenge ... even when we have time for it. So in my next posts, A No-Nonsense Guide to Great Napping and 5 Strategies to Ensure a Great Night's Sleep, I offer some suggestions to help you get the most out of the time you have for sleep.
© 2012 Sherrie Bourg Carter, All Rights Reserved