January 8, 2008, Updated September 13, 2012

At work? An afternoon snooze could be an important key to learning new tasks according to Israeli researchers.Good news for all those sloths out there. According to researchers at the University of Haifa, a 90-minute siesta helps speed up the process of long-term memory consolidation.

In a recent study, Prof. Avi Karni and Dr. Maria Korman of the Center for Brain and Behavior Research at the University of Haifa found that an afternoon nap changes the course of consolidation in the brain. “We still don’t know the exact mechanism of the memory process that occurs during sleep, but the results of this research suggest the possibility that it is possible to speed up memory consolidation, and in the future, we may be able to do it artificially,” said Karni.

Long-term memory is defined as a permanent memory that does not disappear, or that disappears after many years. Long-term memory is divided into two types – memories of “what” (for example: what happened yesterday or what one remembers from an article one read yesterday) and memories of “how to” (for example: how to read Hebrew, how to drive, play basketball or play the piano).

In the study, published in the scientific journal Nature Neuroscience, the researchers worked with two groups of participants. Group members practiced a repeated motor activity which consisted of bringing the thumb and a finger together in a specific sequence. The research examined the “how” aspect of memory in the participants’ ability to perform the task quickly and in the correct sequence. One of the groups was allowed to nap for an hour and a half after learning the task while the other group stayed awake.

The researchers, who worked in cooperation with the Sleep Laboratory at the Sheba Medical Center and researchers from the Department of Psychology at the University of Montreal, found that the group that slept in the afternoon showed a distinct improvement in their task performance by that evening, as opposed to the group that stayed awake, which didn’t exhibit any improvement.

Following an entire night’s sleep, both groups exhibited the same skill level. “This part of the research showed that a daytime nap speeds up performance improvement in the brain. After a night’s sleep the two groups were at the same level, but the group that slept in the afternoon improved much faster than the group that stayed awake,” stressed Prof. Karni.

A second experiment showed that other aspects of memory consolidation are also accelerated by sleep. In previous studies, researchers demonstrated that in the six to eight hours after completing an effective practice session, the neural process of “how” memory consolidation is susceptible to interference. If, for instance, you learn or perform a new task after learning the first, your brain will not be able to successfully remember how to carry out the first task

At the University of Haifa, a third group of participants learned a different thumb-to-finger movement sequence two hours after practicing the first task. As the second task was introduced at the beginning of the six to eight hour period during which the brain consolidates memories, the second task disturbed the memory consolidation process and this group did not show any improvement in their ability to perform the task, either that evening, or the following morning.

When a fourth group of participants was allowed a 90 minute nap between learning the first set of movements and the second, however, they did not show much improvement in the evening, but showed a marked improvement in performance the following morning, as if there had been no interference at all.

“This part of the study demonstrated, for the first time, that daytime sleep can shorten the time “how to” memory becomes immune to interference and forgetting. Instead of six to eight hours, the brain consolidated the memory during the 90 minute nap,” explains Prof. Karni.

While it is clear that this study demonstrates that the process of memory consolidation is accelerated during daytime sleep, Karni said it is still not clear which mechanisms sleep accelerates in the process. The researchers believe, however, that the elucidation of these mechanisms could enable the development of methods to accelerate memory consolidation in adults and to create stable memories in a short time.

Until then, if you need to memorize something quickly or you’ve got lots of different activities to learn how to do at one go, better find some time for an afternoon snooze.


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Jason Harris

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