Does Sleep Have A Core Function?

Written by Anna Sophia McKenney
26 Aug 2008
http://www.medicalnewstoday.com/articles/119129.php

The potential necessary functions of sleep were recently discussed in an article released on August 25, 2008 in the open-access journal PLoS Biology.

While it is largely publicly accepted that sleep is essential, there are still many mysteries surrounding its function and how essential it is. Sleep scientists continue to research these questions and find the core function of sleep, which is discussed in the piece by Chiara Cirelli and Giulio Tononi. This is a complex process can require information on many levels, including cells, organs, and the whole organism. "Everybody knows that sleep is important, yet the function of sleep seems like the mythological phoenix,"says Cirelli.

One theory, referred to as the "null hypothesis," states that sleep simply is a manifestation of a quiet, immobile state known as rest. This theory implies that sleep is not individually important in mammals and birds. The null hypothesis is systematically rejected by the authors through three central postulates: that there are animals that do not sleep, that there are animals that do not need recovery sleep when deprived, and that there are no serious consequences to sleep deprivation.

The first, that there are animals that do not sleep, is rejected by refuting the few commonly cited examples: the bullfrog and the coral reef. They claim that the investigations have not been widely performed and further research is needed, at least, to make the claim that they do not actually sleep. Cirelli explains: "We don't understand the purpose of sleep, but it must be important because all animals do it."

Even dophins, which move continuously, sleep in one hemisphere of the brain at the time, with one eye closed and half of its brain in 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," says Cirelli.

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