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SLEEP. Dement and Kleitman (1930’s). Qu. How do we measure sleep?. Electro-encephalogram ( Head ) Electro-oculogram ( Eye ) Electro-myogram ( Neck ). EEG TODAY. Brain Waves and Sleep Stages. Awake. 1. 2. 3. REM. 4. 0. 1. 2. 3. 4. 5. 6. 7. Hours of sleep.

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Dement and Kleitman (1930’s)

Qu. How do we measure sleep?

  • Electro-encephalogram (Head)
  • Electro-oculogram (Eye)
  • Electro-myogram (Neck)
qu what are the sleep stages















Hours of sleep

Qu. What are the sleep stages?

EEG stages

qu why do we sleep
Restoration Model = Sleep allows us to recharge our bodies and recover from fatigue

Evolutionary/circadian rhythm model Sleep’s main purpose is to increase a species’ chances of survival

Qu. Why do we Sleep?
  • Cognitive model = Sleep is necessary for the consolidation of memory and mental functioning.
sleep deprivation experiments
Sleep deprivation experiments;
  • Peter Tripp radio DJ sleep deprived self for 200 hours.
  • Randy Gardner - sleep deprived for 264 hours under supervision of sleep researcher Dement
sleep deprivation effects
Sleep deprivation effects
  • I.Q drop - about 60 studies have confirmed that one hours loss of sleep leads to a 1-point drop in IQ.
  • Qu. If you skip two hours sleep a night for a week to cram in more revision, how many IQ points will you have dropped?
  • 15 x points - your STM is very poor, you cannot think in complex ways and you loose your flexible thinking for creative answers - you are on auto-pilot.
rem rebound dement
REM Rebound - Dement

Rebound phenomena

Following sleep deprivation, we recover much of our lost sleep but there is some segregation of recovery of different types of sleep.

Following selective SWS or REM deprivation, there is selective recovery

restoration or adaption jim horne 1999 asks
Qu. If the body can repair itself under a wakeful state, what is the main purpose of sleep, physiological repair or neurotransmitter recovery?

Qu. If REM is for neurotransmitter recovery, why do infants spend 50% of their sleep in REM, but by the first year they have half of that (when most learning occurs)?

RESTORATION OR ADAPTION?Jim Horne (1999) asks……
restoration theories
  • Horne (1999) - asks;
  • Qu. What is the point of falling unconscious?
  • Qu. Is sleep is purely restorative, why are there so many variations of sleep patterns across species?
brain development

Evolutionary/circadian rhythm model

Sleep’s purpose = increase the chances of survival

Species sleep patterns are different due to….


Ecological niche


Qu. Do all animals sleep?

All mammals and birds sleep.

Qu. Can you explain these differences?

qu do fish sleep
Qu. Do fish sleep?

Apparently so

Fish, reptiles and amphibians have periods of ‘inactivity’

meddis 1975 predation theory
Meddis, (1975) - Predation theory
  • Sleep has evolved to help species adapt to threats.
  • Patterns of sleep diversify across species due to environmental threats posed, leading to;
      • Sleep pattern?
  • Large predators =
  • Small vulnerable animals =
  • Animals who cannot see in the dark =
webb 1982 hibernation theory
Webb, (1982) - Hibernation theory
  • Sleep evolved to conserve energy
  • Hibernation necessary when food resource are low.
energy consumption issues
Energy consumption issues?
  • Marine mammals do not show REM sleep, perhaps because relaxed muscles are incompatible with the need to come to the surface to breathe.
  • In dolphins and birds, only one brain hemisphere enters SWS at a time— the other remains awake.
evolutionary critiques
Evolutionary critiques?
  • Qu. Can these ideas be tested?
  • Qu. Does sleep serve the same function for all species?
  • Qu. Is sleep an ‘adaptive process’?
  • Qu. What happens if we are deprived of sleep?
cognitive theories
  • Empsom and clark (1970)
  • Sleep - especially REM sleep - facilitates the reinforcement of information in memory.
  • Qu. What would happen if you were deprived of REM sleep during revision?
  • Qu. How would you prove the theory right?
rem and cogntition


Strickgold (1999) found that PET scans reveal a high level of activity between these two structures during sleep.

SWS - activity is one way

REM - info flows other way

strickgold 1999
Strickgold (1999)
  • Method: Students taught a visual discrimination task (learning to spot things in their peripheral vision).
  • They had to do 25 sets in the evening, and another 25 sets in the morning - measured overall improvement.
  • Some were allowed to sleep normally, others were sleep deprived - some SWS, others REM sleep.
  • Results: Normal sleep - improved performance 40%
  • Deprived SWS sleep - Improved 28%
  • Deprived REM sleep - improved only 18%