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Microsoft PowerPoint - Theories of Sleep and Dreaming (1)

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					Theories of sleep & dreaming




                 Mark Illingworth & Emma Pearch
           Why do we sleep?
For AS you need to know 2 theories of sleep:



• Evolutionary Theory
          Evolutionary Theory
                  ---Survival of the fittest (genes)---

• MEDDIS (1979):
         (1979)
        – Researched into the relationships between sleep patterns of
          predatory animals and their prey.
        – Found that prey sleep for less time than predators as being at
          an alert state as much as possible is essential to the prey’s
          survival.
        – Humans have evolved to sleep at night because
          without our eyesight we not only lose our
          productivity but we also become prey.
• WEBB:
        – Looked at cases of prey that can sleep for lengths due to the
          safety of burrowing etc (e.g. Rabbits).
        – In circumstances where we can be relatively sure of
          our safety during sleep, we can then also sleep
          longer.
Evaluating Evolutionary Theory
+ Similar animals sleep in similar ways. (i.e. reptiles do not have REM
  sleep - due to the less developed hypothalamus.)

+ Some animals have evolved their sleep patterns to adapt to their
  environments.



- Surely if alertness is the question, why haven’t we evolved not to
  sleep? Then we could be vigilant 24/7.

- This theory has no explanation for the different cycles of sleep which
  have been proven to occur.

- We can’t test this theory, well, until someone invents a time machine
  so that we can observe changes in human sleep patterns over time.
            Why do we sleep?
 For AS you need to know 2 theories of sleep:



• Evolutionary Theory
               ~~Survival of the fittest genes over time~~



• Restoration Theory
          Restoration Theory
                 ~~Exertion requires regeneration~~



• OSWALD:

      – Looked at how the body recovers most during sleep, with
        peak levels of protein synthesis in cases for the recovery of
        the body as well as general growth.

      – ‘We need to sleep to restore ourselves physiologically
        and psychologically’
Evaluating Restoration Theory
+ All hormones work more effectively at night.

+ After 5/6 sleepless nights, delusions and other psychological problems are
  known to develop.

+ The youngest and oldest people sleep much less as with their lesser
  exertion, they require less restoration.

+ SHAPIRO: Studied marathon runners, who due to their massive exertions,
  required longer sleeping times to restore their bodies.

-   REM sleep is where the brain is often at its most active, so brain energy
    must not be being conserved.

-   Sleep studies are hard to certify as there can be many external factors that
    affect sleep.

-   RYBACK & LEWIS (1971): - Kept active people in a room and told them to
    do nothing, the participants were expected to not need to sleep due to the
    lack of exertion, but they did sleep.
            Why do we sleep?
 For AS you need to know 2 theories of sleep:



• Evolutionary Theory
               ~~Survival of the fittest genes over time~~



• Restoration Theory
               ~~Exertion requires regeneration~~



[SORTED! – Onto the Dreaming then! Only need one of those!]
      Reprogramming Theory
              ~~Further processing new information~~


• EVANS (1984):
        – HERMAN & ROFFWARG (1983): Discovered that after
          spending a day wearing distorting lenses, participants spent
          more time than usual in REM sleep – interpreted as the brain
          taking longer to organise all the new experiences.

        – The brain goes ‘off-line’ during REM sleep and tries to
          make sense of events that have recently occurred.
Evaluating Reprogramming Theory
+ May explain why most dreams are inclusive of recent events, and why
   dreams tend not to make sense.

+ Can explain why old people spend less time in REM sleep. (As they will rarely
   be encountering new things for the first time)

- Foetuses & very young infants spend very much time in REM sleep, though
   they very little if any memories processed which would require sorting out.
           Why do we dream?
 For AS you need to know 1 theory of sleep:



• Reprogramming Theory
                      ~~Further processing new information~~




[SORTED! – Hope this helped, I’m off to sleep now!]

                       No pun intended, its 2:16am,
                       really!

				
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Description: Microsoft PowerPoint - Theories of Sleep and Dreaming (1)