Featured Research

from universities, journals, and other organizations

Exploring The Function Of Sleep

Date:
August 27, 2008
Source:
Public Library of Science
Summary:
Is sleep essential? Ask that question to a sleep-deprived new parent or a student who has just pulled an "all-nighter," and the answer will be a grouchy, "Of course!" But to a sleep scientist, the question of what constitutes sleep is so complex that scientists are still trying to define the essential function of something we do every night.

Is sleep essential? Ask that question to a sleep-deprived new parent or a student who has just pulled an "all-nighter," and the answer will be a grouchy, "Of course!"

Related Articles


But to a sleep scientist, the question of what constitutes sleep is so complex that scientists are still trying to define the essential function of something we do every night. A study published this week in PLoS Biology by Chiara Cirelli and Giulio Tononi addresses this pressing question.

The search for the core function of sleep can seem as elusive as the search for the mythological phoenix, says Cirelli, an associate professor of psychiatry at the University of Wisconsin School of Medicine and Public Health in Madison.

Some scientists argue that sleep is merely a way to impose a quiet, immobile state (rest), and isn't important by itself in mammals and birds. This is the so-called "null hypothesis," and Cirelli and Tononi reject it.

"We don't understand the purpose of sleep, but it must be important because all animals do it," Cirelli says.

There's no clear evidence of an animal species that doesn't sleep, she says. Even the dolphin—which is sometimes held up as an animal that doesn't sleep because it moves continuously—will show "unihemispheric sleep" with one eye closed and one half its brain showing the slow waves characteristic of deep sleep.

"The very fact that dolphins have developed the remarkable specialization ..., rather than merely getting rid of sleep altogether, should count as evidence that sleep must serve some essential function and cannot be eliminated," Cirelli says.

She also argues that sleep is strictly regulated by the brain, because sleep deprivation is followed by a rebound, in which the sleep-deprived animal either sleeps longer, or spends more time in the deeper sleep characterized by large slow brain waves.

Prolonged sleep deprivation has been shown to kill rats, flies and cockroaches. Humans who have a genetic insomnia can also die. In less extreme cases, sleep deprivation affects cognitive function in animals ranging from flies to rodents. Rats kept awake will engage in "micro-sleep" episodes, and sleep-deprived humans tend to fall asleep even in the most dangerous circumstances.

Because it is universal, tightly regulated, and cannot be lost without serious harm, Cirelli argues that sleep must have an important core function. But what?

"Sleep may be the price you pay so your brain can be plastic the next day," Cirelli and Tononi say.

Their hypothesis is that sleep allows the brain to regroup after a hard day of learning by giving the synapses, which increase in strength during the day, a chance to damp down to baseline levels. This is important because the brain uses up to 80 percent of its energy to sustain synaptic activity.

Sleep may also be important for consolidating new memories, and to allow the brain to "forget" the random, unimportant impressions of the day, so there is room for more learning the next day. This could be why the brain waves are so active during certain periods of sleep.

"While there may still be no consensus on why animals need to sleep, it would seem that searching for a core function of sleep, particularly at the cellular level, is still a worthwhile exercise," she concludes.


Story Source:

The above story is based on materials provided by Public Library of Science. Note: Materials may be edited for content and length.


Journal Reference:

  1. Cirelli C, Tononi G. Is sleep essential? PLoS Biol, 2008; 6(8): e216 DOI: 10.1371/journal.pbio.0060216

Cite This Page:

Public Library of Science. "Exploring The Function Of Sleep." ScienceDaily. ScienceDaily, 27 August 2008. <www.sciencedaily.com/releases/2008/08/080825203918.htm>.
Public Library of Science. (2008, August 27). Exploring The Function Of Sleep. ScienceDaily. Retrieved November 1, 2014 from www.sciencedaily.com/releases/2008/08/080825203918.htm
Public Library of Science. "Exploring The Function Of Sleep." ScienceDaily. www.sciencedaily.com/releases/2008/08/080825203918.htm (accessed November 1, 2014).

Share This



More Health & Medicine News

Saturday, November 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Melafind: Spotting Melanoma Without a Biopsy

Melafind: Spotting Melanoma Without a Biopsy

Ivanhoe (Oct. 31, 2014) The MelaFind device is a pain-free way to check suspicious moles for melanoma, without the need for a biopsy. Video provided by Ivanhoe
Powered by NewsLook.com
Battling Multiple Myeloma

Battling Multiple Myeloma

Ivanhoe (Oct. 31, 2014) The answer isn’t always found in new drugs – repurposing an ‘old’ drug that could mean better multiple myeloma treatment, and hope. Video provided by Ivanhoe
Powered by NewsLook.com
Chronic Inflammation and Prostate Cancer

Chronic Inflammation and Prostate Cancer

Ivanhoe (Oct. 31, 2014) New information that is linking chronic inflammation in the prostate and prostate cancer, which may help doctors and patients prevent cancer in the future. Video provided by Ivanhoe
Powered by NewsLook.com
Sickle Cell: Stopping Kids’ Silent Strokes

Sickle Cell: Stopping Kids’ Silent Strokes

Ivanhoe (Oct. 31, 2014) Blood transfusions are proving crucial to young sickle cell patients by helping prevent strokes, even when there is no outward sign of brain injury. Video provided by Ivanhoe
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins