A power nap is a very short sleep that terminates before an individual falls deeper into the slow-wave sleep phase of the sleep cycle. People have been taking power naps to jumpstart their day or to supplement normal sleep, especially when they have accumulated sleep debts.
Neuropsychologists from Saarland University in Germany have further uncovered how taking short-lived slumbers can significantly improve memory performance, especially the retention of learned material in memory.
The neuropsychologists conducted a study that involved participants learning 90 single words and 120 meaningless word-pairs. These participants subsequently performed initial tests that assessed their hippocampus-dependent associative memory (AM) and hippocampus-dependent item memory (IM).
Associative memory involves recalling the relationship between unrelated items—such as the meaningless word-pairs. On the other hand, item memory is recall or recognition of previously presented information.
After the AM and IM tests, the neuropsychologists grouped the participants into two. The first group took a nap that spanned within 90 minutes while the second group or the control group watched DVDs. The entire participants once again performed final AM and IM tests.
The researchers compared the results between the first and second AM and IM tests. Their comparison revealed that both groups performed poorly in the second IM test than the first IM tests. However, the group who took power naps had consistent performance in the first and second AM tests while the control group had performed poorly.
A notable takeaway from the study is that power nap preserves associative memory performance but not item memory performance.
More than this takeaway, however, the neuropsychologists also uncovered the role of power nap and hippocampus in consolidating memory. Note that the hippocampus is a region in the brain that plays an important role in consolidating information from short-term memory to long-term memory.
When recalling the meaningless word-pairs, participants were accessing memory in the hippocampus. The fact that the group that took power naps performed consistently in both pre-nap AM test and post-nap AM test is suggestive that short-lived sleeps can improve associative memory. To be specific, power naps may not increase memory capacity but it helps in the retention of learned material or improve the ability to learn and remember the relationship between unrelated items.
“A short nap at the office or in school is enough to significantly improve learning success,” said Axel Mecklinger, research head and professor at Saarland University. “Wherever people are in a learning environment, we should think seriously about the positive effects of sleep.”
Further details of the study are in the article “Nap sleep preserves associative but not item memory performance” that appeared in the journal Neurobiology of Learning and Memory. Sara Studte and Emma Bridger are co-researchers.