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Posted: 10:11 AM Nov 4, 2006
Sleep Sharpens Memory
Testing supports resting Remember those all-nighters, cramming for the big exams? A new study says without sleep, those facts and figures probably won't stick.
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Remember those all-nighters, cramming for the big exams? A new study says without sleep, those facts and figures probably won't stick.
Nineteen-year-old Kimberly Hagan is a busy college sophomore and a good night's sleep isn't always a top priority.
“I think sleep and college life sometimes don’t mix too well," she says.
Kimberly took part in a recent study that looked at whether sleep can enhance memory. Using computers, study participants learned pairs of vocabulary words. The next morning, researchers asked them to recall what they’d learned.
Dr. Jeffrey Ellenbogen says, "Instead of asking them to just recall the information, as one would normally do, we had them learn a new set of words, meant to disrupt the original words that they learned. And then we had them tested on words that they had learned prior to sleeping."
The study found that sleep strengthens memories even when those memories are challenged.
Dr. Ellenbogen says, "Sleep is helping to stabilize memory, such that the information is resistant to the normal, everyday bombardment of information that comes in and causes us to forget."
That's why all-night studying can leave you forgetful.
Dr. Ellenbogen says, "You might even do OK the next day but I wouldn’t expect that memory to be stable or strong. Don’t expect it to be there for the midterm or the final."
To build on these findings, future research will go in several directions, including the relationship between sleep and memory in different age groups such as high school students and older adults.
Fast Facts:
Sleep
Most adults need seven to ten hours of sleep a night. However, a recent poll by the National Sleep Foundation found 40 percent of American adults are getting less than seven hours of sleep/night on weekdays. On average, most people are sleeping 6.8 hours per weekday night and 7.4 hours on a weekend night.
Lack of quality sleep can take a toll on the body and mind. People who are sleep-deprived have more difficulty paying attention and staying focused. Reaction time is slowed and decision making skills can be impaired. Sleepiness can affect mood and lead to strained family relationships and poor school or work performance. Annually, sleepy drivers are believed to cause more than 100,000 automobile accidents. The National Sleep Foundation estimates daytime sleepiness costs this country about $100 billion.
Memory
There are several different types of memory. Short term memory works like a temporary file and has limited capacity. As new information comes in, old information can be lost or “forgotten.”
Long-term memory can be divided into two different categories. Procedural memory refers to the ability to store and retrieve information related to perception, motor and verbal skills and cognitive thought. Examples of procedural memory are learning to ride a bike or play the piano. Declarative memory refers to factual information that can be consciously recalled. It can be further divided into “episodic memory” (i.e., remembrance of situations, like a first date or vacation) and “semantic memory” (factual information, like addition skills, vocabulary or history).
The Role of Sleep in Memory
Research has shown that sleep is essential to learning and memory. The exact role of sleep in memory isn’t known. However, scientists believe that, during sleep, the brain actively processes, reinforces and relocates new information.
At Brigham and Women's Hospital in Boston, investigators tested the effects of sleep on declarative memory (the ability to remember “facts”). Participants were asked to memorize a series of 20 paired words during evening hours. The next morning (12 hours later), the subjects were given a recall test. Prior to the recall, half of the participants were given a second group of paired words to study. These new words were introduced in an attempt to “distract” the brain, or create interference in recall of the first set of words. To study the effects of sleep, another group of participants was given the first set of words at the beginning of the day and tested later in the day.
The researchers found sleep had an important influence on the ability to recall the first set of words. In the non-interference group (those who didn’t have to learn the second set of words), participants who slept after learning the first set of words had a slightly higher recall rate than those in the non-sleep group (who learned the words the same morning). In the interference group, those who slept had significantly higher rates of recall than the non-sleep learners.
Neurologist Jeffrey Ellenbogen, M.D., says this is the first study to show the benefits of sleep for declarative memory. He says the study may be a “wake-up” call to students who often spend all night studying for exams. Sleep appears to be an important tool for the brain to make stronger connections for stored facts. Those who stay up all night to cram for an exam may perform decently on the next day’s test. However, later recall of the information may be impaired because the brain hasn’t had enough time to “set” those facts.
Web Resources
For general information on sleep:
