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Researchers have looked to animals exhibiting USWS to determine if sleep must be essential; otherwise, species exhibiting USWS would have eliminated the behaviour altogether through evolution. [ 3 ] The amount of time spent sleeping during the unihemispheric slow-wave stage is considerably less than the bilateral slow-wave sleep.
Sleep can follow a physiological or behavioral definition. In the physiological sense, sleep is a state characterized by reversible unconsciousness, special brainwave patterns, sporadic eye movement, loss of muscle tone (possibly with some exceptions; see below regarding the sleep of birds and of aquatic mammals), and a compensatory increase following deprivation of the state, this last known ...
Slow-wave sleep is necessary for survival. Some animals, such as dolphins and birds, can sleep with only one hemisphere of the brain, leaving the other hemisphere awake to carry out normal functions and to remain alert. This kind of sleep is called unihemispheric slow-wave sleep, and is also partially observable in humans. Indeed, a study ...
Among mammals, infants sleep the longest. [44] Human babies have 8 hours of REM sleep and 8 hours of NREM sleep on an average. The percentage of time spent on each mode of sleep varies greatly in the first few weeks of development and some studies have correlated this to the degree of precociality of the child. [45]
Known as slow-wave sleep or stage 3 non-REM sleep, this is the deepest stage of sleep and the hardest to wake up from. Brain activity slows down, muscles and bones strengthen, hormones regulate ...
Unlike most animals, whales are conscious breathers. All mammals sleep, but whales cannot afford to become unconscious for long because they may drown. They are believed to exhibit unihemispheric slow-wave sleep, in which they sleep with half of the brain while the other half remains active. This behavior was only documented in toothed whales ...
Sperm whales have the largest brain mass of any animal on Earth, averaging 8,000 cm 3 (490 in 3) and 7.8 kg (17 lb) in mature males. [28] The brain to body mass ratio in some odontocetes, such as belugas and narwhals, is second only to humans. [29] In some whales, however, it is less than half that of humans: 0.9% versus 2.1%. [citation needed]
The pineal body, known to regulate sleep patterns in humans, is thought to produce the hormones involved in hibernation and aestivation in amphibians. [ 73 ] Tadpoles retain the lateral line system of their ancestral fishes, but this is lost in terrestrial adult amphibians.