Theories of the Functions of Sleep

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  • Created by: rhallett
  • Created on: 09-12-15 16:46
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  • Theories of the Function of Sleep
    • Restoration Theories argue that sleep is needed to reverse the wear and tear and daytime activity; means that sleep has an essential biological function
    • Oswald
      • Argues REM sleep is for brain growth and repair. May help restore NTM levels. Argues REM is do with brain repair partly because people who experience traumas -like drug ODs- have more REM sleep after
      • Stages 3 & 4 are for physical restoration as this is when growth hormones are produced, simulating growth, protein synthesis to occur.
    • Horne
      • Argues brain restoration occurs during the first 4-5 hours of sleep; mainly stages 3 and 4 and some REM sleep which is called 'core' sleep. Agrees with Oswald that sleep restores brain function.
      • Other stages, 1 and 2, are 'optional' sleep as they have no essential function; may help keep animals safe from predation or help conserve energy. Physical restoration occurs during relaxed wakefulness in humans
      • Horne's theory is based partly on the fact that humans deprived of sleep experienced cognitive problems but no physical ones.
    • Evidence
      • +Sleep deprivation on rates using disk over water technique found that they suffered physically eg reduced brain activity, inability to regulate temp and died after 33 days; sleep has an important physical restoration function
        • -Rat deaths may be due to stress not sleep deprivation; rats fell into water as they started to sleep - very stressful
        • -May be hard to extrapolate from rates to humans as rats have simpler brains and biology
        • -Moreover, similar research on pigeons found that sleep deprivation had no ill effects; unclear whether animal research can supports a restoration approach; sleep perhaps has different functions in different species
      • +Shaprio found that people who had run a marathon slept for an hour extra in the 2 nights following, slow wave sleep increased in particular; suggesting sleep restored them physically; thus supports Oswald
        • -However, general research found that intense exercise does not increase amount of time asleep. EG Horne & Minard gave RPs exhausting things to do and didn't find their sleep increased; unclear whether research on exercise supports a restoration approach
      • +Humans deprived of sleep EG Peter Trpp experience a range of cognitive problems eg paranoia, hallucinations; suggests that sleep is required for mental restoration like restoring NTM levels in the brain; supports Oswald and Horne
        • -However these studies are poorly -EG Tripp took drugs to stay awake- and only on individuals; unclear what they really show about the functions of sleep
      • +Growth hormone secreted during the day but a lot is secreted during stages 3 and 4 of sleep; enables protein synthesis to occur suggesting sleep is vital to physical restoration; supports Oswald
      • +All animals appear to sleep, even when it is difficult such as in the case of dolphins; suggesting sleep has an important restorative function

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