An Afternoon Siesta May Boost Memory Through Dreaming


2010-04-22 22:00

Many cultures still participate in a short afternoon nap, called siesta in countries of Spanish influence. Although the custom appears to be largely cultural, several studies have linked the practice with cognitive benefits. The most recent, from the Center for Sleep and Cognition at Beth Israel Deaconess Medical Center in Boston, suggests that an afternoon “power nap” may boost the ability to process and store information.

Lead author Robert Stickgold and colleagues asked 99 college students to memorize a complex maze on a computer. The students were then placed inside a virtual 3-D version of the same maze and asked to navigate to a certain spot. After completing the exercise a few times, approximately half of the participants took a 90-minute nap while the remainder stayed awake, watching videos.

Five hours later, the nappers performed better in the maze than those who had stayed awake. The researchers then narrowed down the nappers into who dreamed during the nap and who did not. Those who dreamed performed 10 times better than those who did not.

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"When you dream, your brain is trying to look at connections that you might not think of or notice when [you're] awake," says Stickgold. "In the dream...the brain tries to figure out what's important and what it should keep or dump because it's of no value.”

The sleeping brain, whether at night or during the day, continues to process information. According to Michael Breus of Arrowhead Health, not involved in the study, if something is particularly relevant or helpful in your life experience, the brain involves the memory network during sleep to help improve performance on the task in the wakeful hours.

As for napping itself, some evidence has suggested that humans become sleepy in the afternoon because of a change in body temperature related to circadian rhythms. Sleepiness during the day is related to poor alertness and performance, and even just 10 minutes can boost mood and mental abilities.

To use sleep to your best advantage for learning, Stickgold suggests, "If you're studying something tough, get the basics down and take a nap. If you dream about it, you will probably understand it better. Or, go to bed a little earlier the night before, wake up early, review the material, and then take a quick nap to solidify your understanding."

Keep in mind though, that naps should not last longer than 45 minutes or occur after 4pm or it will interfere with nighttime sleep.

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