"We don't understand the purpose of sleep, but it must be importantbecause all animals do it," Chiara Cirelli and Giulio Tononi, the study authors say, who describes the search forsleep as like the search for the mythological phoenix.
Some scientists believe that sleep is not important by itself inmammals and birds, and is just a way to impose a quiet and immobilestate. Cirelli and Tononi reject this opinion, pointing to the factthat, so far, there has been no evidence of any animal not sleeping.
Even the dolphin, which is often used as an example of an animal thatdoes not sleep because it keeps moving, has developed its own method ofsleeping. The dolphin shuts down one half of its brain, swimming withone eye closed, and exhibiting the slow waves characteristic of deepsleep.
"The very fact that dolphins have developed the remarkablespecialization . . ., rather than merely getting rid of sleepaltogether, should count as evidence that sleep must serve someessential function and cannot be eliminated," Cirelli says.
Cirelli also points to sleep deprivation, and the after-effect ofhaving gone a long time without sleep, as examples of the necessity ofit. Sleep deprivation has been shown to kill animals like rats, fliesand cockroaches, as well as humans who suffer from genetic insomnia.And when a human rebounds from lack of sleep, they sleep for a longtime to recuperate.
Their hypothesis suggests that sleep acts as a way for the brain toregroup after a hard day. Sleep theoretically gives the synapses –which have been escalating in strength during the day – a chance toslow down again, and return to a base level. given that the brain uses80% of its energy in order to keep the synaptic activity happening,there is an obvious need for the brain to rest.
They also suggest that sleep allows for the consolidation of newmemories, and the trashing of older, random and unimportant memoriesfrom the day passed. this theoretically allows for more learning thefollowing day. "While there may still be no consensus on why animalsneed to sleep, it would seem that searching for a core function ofsleep, particularly at the cellular level, is still a worthwhileexercise," Cirelli concludes.
Posted by Josh Hill.
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Source: http://www.physorg.com/news138941239.html