one reason for sleep might be toxin removal

brain cells shrink during sleep to open up the gaps between neurons and allow fluid to wash the brain clean.

Source: BBC News - Sleep 'cleans' the brain of toxins
added 2013-10-17T21:23:35Z by anders

70% of Americans are sleep deprived

70 percent of Americans who the National Sleep Foundation estimates get less than the generally recommended eight hours of sleep per night

Source: Snorting a Brain Chemical Could Replace Sleep
added 2012-07-07T10:47:20Z by anders

sleep replacement drug

A nasal spray containing a naturally occurring brain hormone called orexin A reversed the effects of sleep deprivation in monkeys, allowing them to perform like well-rested monkeys on cognitive tests.

Source: Snorting a Brain Chemical Could Replace Sleep
added 2012-07-07T10:46:15Z by anders

sleeping shortly after learning new information improves retention

At 24 hr retest, with all subjects having received both a full night of sleep and a full day of wakefulness, we found that memory was superior when sleep occurred shortly after learning rather than following a full day of wakefulness.

Source: PLoS ONE: Memory for Semantically Related and Unrelated Declarative Information: The Benefit of Sleep, the Cost of Wake
added 2012-03-25T22:15:45Z by anders

hypnopompic

A hypnopompic state (or hypnopomp) is the state of consciousness leading out of sleep

opposite of hypnogogia, the state leading into sleep

Source: Hypnopompic - Wikipedia, the free encyclopedia
added 2012-03-23T12:04:58Z by anders