RELATED: If You Do This When Getting Dressed, It May Be a Sign of Dementia. Scientists have long believed that a good night’s sleep is associated with the consolidation of memories. Now, a new study published this month in the Nature partner journal NPJ: Science of Learning has confirmed that longer durations of slow-wave sleep can measurably improve memory. The researchers assembled a group of 24 subjects aged 18 to 31 years old, and asked them to memorize 80 faces and names—40 from a hypothetical Latin American history class and another 40 from a Japanese history class. The subjects then took daytime naps with an electroencephalogram (EEG) to monitor their brain waves, and were read some of the names aloud during the slow-wave phase of sleep. When they woke up, the subjects were asked to recall the names they had learned prior to sleep. The researchers found that “people’s name recall improved significantly when memories of newly learned face-name associations were reactivated while they were napping.” The team concluded that “memory benefits were positively correlated with the duration of stage N3 sleep (slow-wave sleep) and negatively correlated with measures of sleep disruption.” Successful recall was dependent on “ample and undisturbed slow-wave sleep,” the researchers wrote. RELATED: If You’re Sweating at Night, Get Your Blood Checked, Experts Warn. Sleep occurs in two forms, REM sleep (which accounts for 20 percent of sleep) and non-REM sleep (which accounts for the remaining 80 percent). Non-REM sleep is broken up into four stages: stage one being the lightest sleep and stage four being the deepest. Slow-wave sleep—the stage in which we seem to consolidate memory—occurs in the third and fourth stage.ae0fcc31ae342fd3a1346ebb1f342fcb Though the memories of the NPJ study subjects were externally reactivated during this sleep stage, experts believe that the brain also does this naturally while you sleep. “Over a typical night of sleep, a multitude of such memories are presumably consolidated, each reactivated to improve future retention,” says a 2021 study published in the journal Communications Biology. In fact, another 2021 study published in Frontiers in Behavioral Neuroscience determined that targeted memory reactivation (TMR) had little affect on subjects’ problem solving abilities. They found that those who experienced uninterrupted slow-wave sleep reaped the same cognitive benefits as those who were given TMR cues to boost memory. This seems to suggest that uninterrupted slow-wave sleep can improve cognitive function—even without an external nudge from researchers. According to The Sleep Association, there are several things you can do to achieve longer periods of deep sleep. “The most important thing that you can do to increase your amount of deep sleep is to allow yourself adequate total sleep time. Often, individuals will deprive themselves of adequate total sleep. In addition to reducing deep sleep, REM sleep is also shortened,” their experts explain. Additionally, they suggest building some period of “vigorous exercise” into your daily routine, noting that several studies have found that it helps to “increase or consolidate deep sleep.” Following a healthy diet—in particular a lower carb diet—has also been shown to increase slow-wave sleep, the sleep authority says. For more health news sent directly to your inbox, sign up for our daily newsletter. Experts say that your psychological state before bed can also affect how long you achieve slow-wave sleep. The ideal mental state for sleep is one of “serenity,” in which you feel “safe, comfortable and loved,” Rafael Pelayo, a clinical professor of psychiatry and behavioral sciences at the Stanford Center for Sleep Sciences and Medicine, recently told Newsweek. “When that’s happening, you have the luxury of being able to sleep deeply. If you go to sleep in a state of uncertainty of any kind—it doesn’t matter what you’re uncertain about, it could be something as simple as leaving the front door unlocked or thinking about whether your alarm is on or not—the brain will react by causing you to sleep as lightly as possible,” Pelayo said. For this reason, it’s important to resolve as many minor issues as you can before bedtime in an effort to ease your mind. Keeping a journal or writing up a “to-do” list for the next day may help you set your worries aside until the following day. “For most people, the only time they are alone with their thoughts is when they’re in bed. So, they’re in bed saying, ‘I gotta take care of this, I can’t forget to do this.’ Now you’re telling your brain to remember something, which is not allowing your body to go to sleep,” Pelayo warned. Instead, let the little things go for a better night’s sleep—and improved memory. RELATED: If You Dream About This, Call Your Doctor Immediately.
