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the function of sleep

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Many sleep theories have been proposed over the years. However, most of them belong to two broad classes of theory. The first theory that will be discussed is the recovery or restoration theory. All animals' sleep, which suggests that sleep, has some important function. Also the fact that the part of the brain which governs sleep is the oldest, so therefore marks sleep out as a fundamental requirement of all animals. Different species have different sleep requirements. They either sleep little and often or for long periods of time; or they sleep during the day or the night. This suggests sleep is an evolutionary adaptation to environmental conditions. An important function of sleep is probably to save energy and for the restoration of tissue. These theories focus on the benefit of sleep for the physiological system. Sleep may serve to restore psychological functions. If physiological restoration is the function of sleep, we would expect: sleep deprivation would have serious effects, animals that use more energy are more likely to sleep more, and more sleep would be required after physical exertion. ...read more.


Horne and Minard tried to exhaust their participants, and found they went to sleep faster but not for longer. It is purposed people who take little exercise would sleep less than those who take an average amount of exercise. There is little evidence for this. There is a considerable amount of support for this study but also problems or inconsistencies. If restoration was the only function of sleep we would expect to find consistent effects from sleep deprivation. The inconsistent effects may be due to the fact that only some aspects of sleep provide a physiological function. Also if this was the case, we would expect people who are more active to require more sleep, so therefore a mix of findings cannot full support this. The theory however, does support that it is impossible to go without sleep and remain ok, this shows face validity. The importance of SWS4 sleep and REM is also supported. After sleep deprivation there was a greater recovery of REM sleep and SWS4 sleep. This can bring to conclusion that the function of sleep is vital for restoration of the body and brain, but due to lack of evidence, whether this is the main function is questionable. ...read more.


this seems inconsistent with adaptive theories of sleep. However, those at more danger from predators may benefit from keeping themselves vigilant. It is impossible to falsify Meddis' theory. To evaluate, we have already seen that there are problems with the predation theory as it is non-falsifiable. You cannot possibly predict an evolution change. There are also problems with applying this theory to human sleep. If the function of sleep was due to evolutionary factors why hasn't there been some move in the direction of less sleep when today there would be enormous advantages for an individual who needed very little sleep. The explanations in this theory are only of how animals fit sleep in to their lives. The theory also does not explain the function of complex neural activity during sleep. In conclusion sleep is generally less crucial according to adaptive theorists, in contrast to the recovery theorists who believe sleep is absolutely essential. Horne made the point that sleep probably serves different purposes in different species. Therefore no theory is likely to be adequate. It could be argued that the adaptive approach focuses on when different species sleep. ...read more.

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