Sleep and Memory

Several mornings each week, Liz, a Harvard freshman from Toronto, Ontario, rises before 6:00 a.m. to join her teammates for rowing practice. On days like these she seldom sleeps more than seven hours per night, but it's not for lack of trying. In contrast to the college student stereotype, Liz often forgoes opportunities to socialize in order to get her schoolwork done and still get to bed at a reasonable time. Even without knowing just how important sleep is to her ability to learn, she tries to make time for it. 

Only a month and a half into her first semester at college, Liz already wishes she had more time for sleep. The problem is: "You never feel like you've done enough," she says, referring to her school demands. "If you're not working, you feel like you should be. There's always more to do." For Liz, the many demands on her time include her chosen sport, as well as activities like studying for optional, extra-credit exams that she and her peers have come to view as mandatory for anyone trying to excel. 

A Snapshot of Sleep in College

Of course, Liz isn't alone. College students represent one of the most sleep-deprived segments of our population. Course work, sports and other extracurricular activities, and newfound independence all conspire to rob students of sleep. A 2001 study found that only 11 percent of college students slept well consistently, while 73 percent experienced at least occasional sleep issues.¹  A 2007 survey by the American College Health Association found that 40 percent of students felt well rested no more than two days per week.²  No longer considered a harmless aspect of college life, poor sleep is now thought to have a significant impact on memory and learning. 

Basics of Learning

Learning involves three distinct brain processes: acquisition, consolidation, and recall. 

• Acquisition is the process by which the brain receives information—be it a list of facts or the proper technique for shooting a free-throw—and stores this information within its neural circuits as a memory. 
• Consolidation is a process that can extend over minutes, hours, or even days, during which connections in the brain are strengthened, extended, and in some cases even weakened, so that a memory ends up in a more stable and useful form. 
• Recall is the last important step in learning, in which the brain accesses and utilizes stored information, often bringing memories back to mind.

During sleep, your brain is taking your memories, reactivating and looking at them again, and storing them in a more efficient and effective form.

-Dr. Robert Stickgold

The Sleep Connection

Inadequate sleep negatively affects all three learning processes. Acquisition and recall suffer in the most recognizable way. It is simply more difficult to concentrate when we are sleep deprived; this affects our ability to focus on and gather information presented to us, and our ability to remember even those things we know we have learned in the past. The less obvious—but possibly more profound—impact of sleep deprivation on learning is the effect that many sleep researchers think it has on memory consolidation.

Although no one knows exactly how sleep enables memory consolidation, a number of studies have shown that a reduction in total sleep time or specific sleep stages can dramatically inhibit a person's ability to consolidate recently formed memories.^3,4,5  Poor sleep appears to affect the brain's ability to consolidate both factual information—such as what you had for breakfast or that Paris is the capital of France—and procedural memories about how to do various physical tasks—such as riding a bicycle or playing the piano. Research suggests that the most critical period of sleep for memory consolidation is the one immediately following a lesson.⁶  If this opportunity is lost—such as when a student pulls an "all-nighter"—it generally can’t be made up. Even if sleep is "recovered" on subsequent nights, the brain will be less able to retain and make use of information gathered on the day before the all-nighter.

Making Time for Sleep

These findings have shed new light on the importance of making time for sleep, not only for college students, but for anyone who wants to continue to learn. However, that doesn't mean finding the time for sleep is always easy. For many people—even those who recognize the importance of sleep—balancing work, school, family, social activities, and personal time can be difficult, and sleep is often one of the first activities to get squeezed out.

Early in her first semester at Harvard, Liz feels like she is maintaining a healthy balance, but just barely. Striving to get the most out of her time in college, she admits that it's sometimes hard to see sleep as an important part of her scholastic and athletic objectives. But that's exactly what many researchers say sleep is. Rather than thinking of sleep as wasted time or even time off, they say, we should instead view sleep as the time when our brain is doing some of its most important work.

For more on this topic, see Sleep, Learning, and Memory in the Healthy Sleep module.

Sheila, a mother of two and an attorney, found that getting more sleep helped improve her focus and effectiveness at work. To learn more, see Sheila’s Balancing Act.

References

1. Buboltz WC, et al. Sleep Habits and Patterns of College Students. Journal of American College Health. 2001. 50: 131–135.
2. American College Health Association, National College Health Assessment, Fall 2007 Report. 
3. Walker MP, et al. Sleep-dependent Motor Memory Plasticity in the Human Brain. Neuroscience. 2005; 133(4): 911-7.
4. Stickgold R, Walker MP. Memory Consolidation and Reconsolidation: What is the Role of Sleep? Trends Neurosci. 2005 Aug; 28(8): 408-15.
5. Ellenbogen JM, et al. The Role of Sleep in Declarative Memory Consolidation: Passive, Permissive, Active or None? Curr Opin Neurobiol. 2006 Dec; 16(6): 716-22. 
6. Walker MP, Stickgold R. Sleep-dependent Learning and Memory Consolidation. Neuron. 2004 Sep 30; 44(1): 121-33.