昼寝が記憶力を強化する

 45分の昼寝が記憶力を強化するとの研究。言語的な情報(言語的な記述・事実・意味)が記憶される『宣言的記憶(declarative memory)』に関係する。睡眠により、こうした宣言的記憶が簡単に呼び出せるようになる。
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A Daytime Nap Can Boost Memory
But the shut-eye only helps with material that was learned well, study suggests
By Steven Reinberg, HealthDay Reporter
http://health.msn.com/health-topics/neurological-cognitive-health/articlepage.aspx?cp-documentid=100189996
画像FRIDAY, Feb. 1 (HealthDay News) -- A 45-minute midday nap can help boost your memory and remember facts, but only if you learned them well in the first place, a new study suggests.

This type of memory is called "declarative memory" and applies to standard textbook learning and knowledge, in contrast to "procedural memory," which applies to skills. Sleep appears to help "set" these declarative memories and make them easier to recall, the researchers said.

"Sleep appears to have an impact on what is learned well, but not so much when one is not motivated to learn," said lead researcher Matthew A. Tucker, a postdoctoral fellow at Harvard Medical School's Center for Sleep and Cognition.

For the study, 33 people were trained with certain declarative memory tasks. After the training, 16 took a non-REM nap, while 17 stayed awake and watched a movie. Later the same day, all the participants were tested. The tests included memorizing words, memorizing a maze and memorizing a complex line drawing.

Tucker's team found that over three very different declarative memory tasks, taking a nap improved performance compared with staying awake. However, napping only worked for people who had really learned the task well in the first place.

"The nap group performed better overall than the awake group, but the difference wasn't significant," Tucker said. "However, when we looked at individual performance during training, we found those who did better during training benefited from napping," he said.

In addition, people appeared to perform well on one task only, but not all three, Tucker said. "There is likely a basic level of learning that has to be attained before sleep can have an impact on performance," he said.

The findings were published in the Feb. 1 issue of the journal Sleep.

Tucker thinks that taking a nap may actually improve one's memory of facts if one is motivated to learn. "There is a lot of data starting to come in that there are benefits from naps on memory," he said.

Sara Mednick, an assistant professor at the University of California, San Diego's Laboratory of Sleep and Behavioral Neuroscience, said the new study is further proof of the role of sleep on memory and learning.

"This paper is further evidence of how sleep, specifically naps, can be a tool for memory consolidation," she said. "Interestingly, the data shows that not all subjects utilize sleep for consolidation to a similar extent."

More information

For more on the importance of sleep, visit the National Sleep Foundation.

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Enhancement of Declarative Memory Performance Following a Daytime Nap Is Contingent on Strength of Initial Task Acquisition
Volume : 31 Issue : 02 Pages : 197-203
Matthew A. Tucker, PhD; William Fishbein, PhD
http://www.journalsleep.org/ViewAbstract.aspx?citationid=3463
Laboratory of Cognitive Neuroscience and Sleep, Department of Psychology, Program in Cognitive Neuroscience, The City College of the City University of New York, New York, NY

Study Objectives:

In this study we examined the benefit of a daytime nap containing only NREM sleep on the performance of three declarative memory tasks: unrelated paired associates, maze learning, and the Rey-Osterrieth complex figure. Additionally, we explored the impact of factors related to task acquisition on sleep-related memory processing. To this end, we examined whether testing of paired associates during training leads to sleep-related enhancement of memory compared to simply learning the word pairs without test. We also examined whether strength of task acquisition modulates sleep-related processing for each of the three tasks.

Subjects and Procedure:

Subjects (11 male, 22 female) arrived at 11:30, were trained on each of the declarative memory tasks at 12:15, and at 13:00 either took a nap or remained awake in the sleep lab. After the nap period, all subjects remained in the lab until retest at 16:00.

Results:

Compared to subjects who stayed awake during the training retest interval, subjects who took a NREM nap demonstrated enhanced performance for word pairs that were tested during training, but not for untested word pairs. For each of the three declarative memory tasks, we observed a sleep-dependent performance benefit only for subjects that most strongly acquired the tasks during the training session.

Conclusions:

NREM sleep obtained during a daytime nap benefits declarative memory performance, with these benefits being intimately tied to how well subjects acquire the tasks and the way in which the information is acquired.

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