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We’ve all had the experience of having our memory fail us, whether it’s forgetting a name, struggling to remember what you did the day before, or wandering in search of a pair of keys. Before you ascribe that fuzzy memory to a “senior moment,” or to the frenetic pace of daily life, try putting your head to the pillow for a good night’s rest. Sleep—how much you get, and how well you sleep—can have a powerful effect over memory.
When we talk about memory and its relationship to sleep, we’re talking about the intersection of two complicated and dynamic physiological processes—processes that science is still working to understand. Broadly speaking, we can talk about the memory process as having three distinct phases:
Acquisition: taking in new information
Consolidation: storing information that’s been acquired
Recall: retrieving memory from storage
Sleep can play a role in helping—or hindering—each of these aspects of memory. Sleeping well, and avoiding sleep deprivation, can make a real difference in your ability to take in new information—essentially, to learn. If you’ve ever tried to study for a test or complete a work project while short on sleep, you’ve experienced the obstacles that sleep deprivation can have on memory acquisition. Even a very short period of sleep deprivation can diminish your capacity to form new memories in everyday learning.
One recent study illustrates the possible benefit of sleep to skill learning and the formation of new memories. Scientists studying the neural activity of mice found that a period of sleep immediately after learning a new skill encouraged the growth of synapses in the brain that were specifically related to that new learning. Tested on performance after periods of 1 and 5 days, mice that slept after the initial learning performed twice as well on the newly learned task than mice that had not slept.
Sleep is also important to your ability to recall memories you’ve already made. Research indicates that recall of both short-term working memory as well as long-term memory of different forms are impaired by lack of sleep. A sleep-deprived brain is less effective at memory retrieval, while staying well rested can help protect and improve this “remembering” phase of memory.
While both memory acquisition and memory recall are influenced by sleep, it is the middle phase of the memory process—consolidation—that actually occurs during sleep itself. Memory consolidation takes new knowledge you’ve acquired and stabilizes that information, preserving it for future recall and helping to protect it from disruption or degradation over time. Memory consolidation that takes place during sleep not only secures memory for future retrieval, but also appears to free up the learning centers of the brain in preparation to take in new batches of information in the next waking day. Scientists are still discovering how memory consolidation works during sleep, but it’s believed that memory consolidation occurs during several different stages of sleep throughout a night’s rest. The slow brain wave oscillations and sleep spindles that are characteristic of deep sleep (also known as slow-wave sleep), appear to play a critical role in memory consolidation, particularly for forms of memory that involve the brain’s hippocampus. The relationship between REM sleep and memory is especially complicated, and still not well understood. But REM sleep, with its high levels of brain activity and dreaming, appears to also be important to the processing and consolidation of some types of memory.
The large and growing body of research devoted to the relationship between memory and sleep suggests that a routine of sleeping well can have a positive, protective effect on memory. Keep in mind that both the quantity and the quality of sleep are important to memory function. Here are some basic strategies that can help you sleep both more and better:
Establish a sleep routine. A consistent bed time—one that allows for 7-8 hours of nightly rest—is the foundation of a strong sleep routine, and can help you avoid the sleep deprivation that interferes with memory and other cognitive functions.
Be thoughtful about consumption. Avoiding stimulants such as caffeine and alcohol within several hours of bedtime can help improve sleep quantity and quality. Not only can these substances make it more difficult to sleep, they can disrupt normal sleep cycles, and may alter time spent in the stages of sleep that are most important to memory consolidation. Eating heavily in the evenings, and eating late at night, can also disturb sleep quality and lead to restless, interrupted sleep.
Ease your stress. Managing daily stress is also critical for healthy, high-quality sleep. Worry and anxiety are among the most common sources of poor and insufficient rest, leaving you with a tired body and tired mind at the beginning of the next day.
When you’re tempted to stay up late for the sake of being productive, in mind that you and your memory ultimately will be better served by getting a good night’s sleep. Well rested, you’re more likely to feel better, perform better, and to remember more.
Michael J. Breus, PhD
The Sleep Doctor™