Under the Hood

A Power Nap In School And The Office May Help You Retain Learned Memory Better

How to improve memory
Here's one more reason people should be encouraged to get short sleep in the middle of the day. Tatiana Bulyonkova, CC BY-NC-SA 2.0

Power naps influence memory recall, according to a new study out Saarland University in Germany.

Researchers cited studies that have shown short naps (about an hour) can positively influence memory performance. But, they wanted to better understand the role naps play in both associative and item memory. The American Psychological Association defines associative memory (AM) as “the ability to learn and remember the relationship between unrelated items, such as the name of someone we have just met.” Item memory (IM), on the other hand, refers to the ability to recall items, such as the names of friends, phone numbers, even an ATM password.

In which case, researchers taught and tested 41 participants 90 single words and 120 word pairs, such as “milk-taxi.” The word pairs were purposefully unrelated so participants would need to access the specific memory of the corresponding episode in the brain’s hippocampus (where it’s believed memories are consolidated). After their memory tests, half of the participants were allowed to sleep and the rest watched a DVD.

When participants were re-tested after their nap and movie, those who took a nap retained more word pairs in memory than those who didn’t take a nap. In other words, their AM (not IM) had improved. In fact, researchers found a short sleep lasting between 45-minutes and an hour produced a five-fold improvement in memory recall.

“The control group, whose members watched DVDs while the other group slept, performed significantly worse than the nap group when it came to remembering the word pairs,” Dr. Axel Mecklinger, who supervised the study, said in a press release. “The memory performance of the participants who had a power nap was just as good as it was before sleeping, that is, immediately after completing the learning phase.”

Despite power nap participant's memory performance not changing much before and after sleep, their recall was constant and consistent with researcher's predictions.

Additionally, researchers were able to better study sleep spindles, “a particular type of brain activity…that plays an important role in memory consolidation during sleep." Sara Studte, lead study author and a graduate biologist specializing in neuropsychology, suspected these sleep spindles work to consolidate certain memory types. And she found they do.

Successfully learning and retrieving information before and after sleep related to spindle density during a power nap, Studte said. Put it another way: the greater number of sleep spindles seen in a participant's brain, the stronger their AM was.

Source: Studte S, Bridger E, and Mecklinger A. Nap sleep preserves associative but not item memory performance. Neurobiology of Learning and Memory, 2015.

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