Many researchers might disagree with Shakespeare's suggestion that sleep, "Nature's soft nurse," steeps the senses in forgetfulness. Instead, they have come to believe slumber actively helps our brains consolidate what we learn and remember.
To be clear, not all researchers agree on sleep's role in memory consolidation. But the research in favor of the power of sleep may be mounting.
Experts distinguish between two broad categories of sleep based, in part, on brain wave patterns measurable using the electroencephalogram (EEG). Delta waves, the slowest rhythm of all brain waves, predominate during the deepest part of non-rapid eye movement (non-REM) sleep. Meanwhile REM sleep, the kind of sleep most often associated with dreaming, is characterized by bursts of rapid eye movement. Over the course of a good night's sleep, non-REM and REM sleep alternate cyclically.
Sleep and memory
While non-REM and REM sleep are both critical for cognitive functioning, they may be important in the encoding and consolidation of different kinds of memories. Non-REM sleep may be particularly significant for declarative memory, our ability to recall the kind of fact-based information we might be tested on in school. Meanwhile, REM sleep has been associated with procedural memory for how to do things like riding a bicycle or learning a new dance step.
Studies suggest depriving people of an adequate amount of sleep hampers their ability to learn new information. For example, researchers at Harvard Medical School found that a night of sleep deprivation reduces activity in the hippocampus, which results in poorer memory retention.
And, sleeping after something has been learned appears to help the brain consolidate new information in long-term memory. In one of their sleep studies, researcher Kenichi Kuriyama and his colleagues (also at Harvard Medical School) had participants get a night's rest after doing a finger-tapping task on a computer keyboard for 12 minutes. They found that the participants' performance significantly improved the following day on parts of the task that had been most difficult for them.
Do naps count?
The benefits of napping are also being investigated. In another study, the Harvard Medical School researchers found that people who napped for 60 to 90 minutes after learning the finger tapping task improved, while those who stayed awake didn't. However, the nappers' advantage disappeared overnight, once those who'd stayed awake were given a chance to catch some shut eye.
Sleeping, age, and memory
Experts agree that most people need seven or eight hours sleep to feel fully rested.
Unfortunately, the ability to fall and stay asleep is often a casualty of aging. Reports of sleeplessness begin to increase in the 30s. And as the years pass, adults tend to spend more and more hours lying in bed waiting for the sandman. By age 60, getting a solid uninterrupted night of sleep can be a cause for celebration.
According to surveys, more than 30% of adults over the age of 60 say they have trouble sleeping and, not surprisingly, sleep-deprived older adults account for a disproportionate share of the prescriptions doctors write for sleeping medications.
The fact that aging is associated with changes in both memory and sleep hasn't gone unnoticed. Researchers are investigating whether age-related declines and slowing in memory performance are associated with increased rates of insomnia and changes in sleep patterns among older age groups. There is some preliminary evidence that the two are related.
How to get a good night's sleep
Here are some tips from the experts for getting a good night's sleep:
- Fitness seems to help regulate sleep, so stay committed to your exercise program.
- Do not drink alcohol, coffee, cola, and tea after 7pm or 8pm.
- Drink a glass of warm milk at bedtime.
- Go to bed only when you are tired.
- Make sure your bedroom is quiet and dark.
- Learn some deep relaxation techniques.
- Don't try to force sleep. Let it overpower you.
- Read or do a relaxing hobby for a while if you can't sleep or wake up during the night.
- Limit the number of hours you spend in bed, even if you've slept badly.
- If you had a sleepless night, try taking a short nap of no more than 45 minutes.
Other ways you might improve your memory and cognition
- Use BrainHQ, a brain training system with online exercises that are clinically proven to sharpen both auditory and visual memory. (If you only have time for one, pick BrainHQ over crosswords and other puzzles, since a recent study showed BrainHQ is significantly more beneficial for the brain than puzzles)
- Get regular physical exercise—it’s good for the brain as well as the body
- Eat with an eye for brain health—dark chocolate and red wine are both on the brain-healthy list!
- Be social—studies show people who maintain an active social life are typically brain healthier, and happier, too.