1. SLEEP

2. EEG TODAY
Mummy, I Can’t Sleep!

3. What you need to Know Two theories about the function of sleep
What happens during sleep and how this might relate to function.
Evidence and evaluation points for each theory
Evaluation using a possible THIRD theory

4. Objectives Lesson 1 Mini-test
To know the stages of sleep (1-4 +REM) and brain activity related to each one
To be clear about the difference between REM and NREM Sleep
To be able to describe Restoration Theory of sleep with supporting evidence.

5. Qu. What are the sleep stages?1 2 3 4 5 6 7
Awake
Hours of sleep
REM
EEG stages

6. Qu. How do we measure sleep?
Electro-encephalogram (Electrical Activity)
Electro-oculogram (Eye Movement)
Electro-myogram (Muscle tension)

7. Brain Waves and Sleep Stages

8. Stages 1 & 2 Relaxed state – easily woken
Heart rate slows & temperature drops
Alpha & Theta waves
Sleep spindles (stage 2)
Brain waves are quite fast

9. Stages 3&4 Slow Wave Sleep
Deeper Sleep – harder to wake
Heart rate slows further
Temperature keeps dropping
Some slow Delta Waves (50%+ in stage4)
Metabolic rate lowest
Growth hormone produced

10. REM Sleep Paradoxical Sleep Brain active - body paralysed
Faster waves – like waking
Increase in oxygen consumption, blood flow and neural firing
Rapid Eye Movements
Hardest to wake from

11. 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

12. Objectives – Lesson 2 Mini-test
To evaluate Restoration theory in two ways:
Discussing supporting and opposing evidence
Discussing the evidence that relates to the predictions of restoration theory
psychlotron.org.uk

13. Restoration Theory
The function of sleep is to allow body to be repaired and restored
Oswald (1980)
REM essential for brain recovery
SWS essential for body repair
psychlotron.org.uk

14. The importance of SWS Growth Hormone is secreted during SWS
Sassin et al found that when we sleep during the day and are awake at night the release of GH is also reversed.
This supports the idea that GH is linked to SWS
Krueger et al (1985) found a link between lack of SWS and reduced immune functioning.

15. What is different about infant and old people sleep patterns?

16. Importance of REM sleep
BRAIN DEVELOPMENT
In babies REM appears to be important for brain growth
Length of REM in a species related to maturity at birth
Less mature at birth = more REM needed
CHECK – who needs more REM – a platypus or a dolphin?
Evaluate: Is this direct evidence?

17. Importance of REM sleep
NEUROTRANSMITTERS
There is break in neurotransmitter release
This allows neurons to regain sensitivity
Support
MAOI’s increase levels of monoamines (eg serotonin and dopamine)
Side effect – REM is abolished
Why? Increase in monoamines mean receptors don’t need revitalising
So – no need for REM (Siegel 2003)

18. Siegal and Rogawki (1988)
Sleeping may be a way of conserving & replenishing brain chemicals known as neurotransmitters. Over the day these levels fall. During REM sleep neurons synthesize new neurotransmitter for release during waking.
EVALUATE – compare with Siegel 2003: they seem to say different things

19. Importance of REM sleep
MEMORY CONSOLIDATION
REM consolidates procedural memory
SWS consolidates semantic memory and episodic memory
Stickgold (2005)
Evaluation – Relevant to Restoration Theory? How?

20. Oswald – Supporting evidence
(1983) Found that tissue growth in skin takes place more quickly when we are asleep. REM sleep is important for brain growth & repair. SWS important for bodily growth & repair.
(1969) Patients recovering from drug overdoses. Significant increase in quantity of REM sleep which is indicative of recovery processes.
EVALUATE- other possible conclusions?

21. Plenary questions How is sleep measured?
What does Restoration theory say about the purpose of sleep?
Give two reasons why SWS is important.
What distinction does Oswald make about the purposes of REM and SWS?
What evidence supports the idea that REM sleep is linked to neurotransmitters?

22. Restoration theory Main predictions:
Deficits in functioning during sleep deprivation
Rebound following deprivation
Increase in REM during brain growth, reorganisation & repair
Increase in SWS during illness, recovery from injury
psychlotron.org.uk

23. Restoration theory Main predictions:
Increased Exercise – increased sleep:
Shapiro (81) Supports – How?
Horne & Minard (85) opposed – How?
psychlotron.org.uk

24. Peter Trip Video

25. 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
May have been getting MICROSLEEP

26. 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.

27. Rebound Generally, people catch up on sleep following deprivation
Not all lost sleep is reclaimed
About 70% of lost SWS and about 50% of lost REM typically recovered
Only REM and SWS sleep is necessary
psychlotron.org.uk

28. Growth & reorganisation
Reduction in sleep over lifespan
Highest in infants; highest REM in early years
Some changes in adolescence
5yrs
REM
NREM
24 hour period
psychlotron.org.uk
Age

29. Illness & injury
Sleep does increase during illness and recovery from injury
Total sleep time increases during illness
REM increases during recovery from brain injury, ECT & drug withdrawal
SWS deprivation can cause physical symptoms
psychlotron.org.uk

30. COGNITIVE THEORIES USE FOR EVALUATION 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?

31. Stickgold (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%

32. Test
Why does Michael Corke’s story strongly support restoration theory?
What Shapiro et al find about the effect of increased exercise?
What does the ‘rebound effect’ show about which types of sleep are important?
What is REM sleep important for according to Stickgold?

33. Objectives – Lesson 3 Mini-test
To be able to describe evolutionary theory using the ideas of energy conservation, foraging requirements and predator avoidance.
To understand the theories of Webb and Meddis

34. Evolutionary/circadian rhythm model
Sleep’s purpose = increase the chances of survival
Species sleep patterns are different due to….
BRAIN DEVELOPMENT
BODY SIZE
Ecological niche

35. Qu. Can you explain these differences?
Qu. Do all animals sleep?
Mammal
Hrs of sleep/day
Giant Sloth
Tree Shrew
Cat, Hamster
Mouse, rat, squirrel
Hedgehog
Humans, rabbit, pig
Cow, Goat, Elephant
Horse, Roe deer 20 15 14 13 10 8 3 2
All mammals and birds sleep.
Qu. Can you explain these differences?

36. Qu. Do whales sleep?
Apparently so

37. Fish, reptiles and amphibians have periods of ‘inactivity’
Qu. Do fish sleep?
Apparently so
Fish, reptiles and amphibians have periods of ‘inactivity’

38. SWS and REM sleep patterns in mammals

39. Evolutionary Theory of Sleep
THREE KEY ASPECTS
Energy Conservation
Foraging Requirements
Predator Avoidance (“Waste of Time”)

40. Webb, (1982) – Energy Conservation
Hibernation Theory
Sleep evolved to conserve energy
Period of enforced inactivity - using less energy (Like hibernation)
Important for animals with high metabolic rates

41. Foraging Requirements
Sleep limited by food requirements
Herbivores tend to eat large quantities of low nutrition food e.g grass and therefore need to eat a lot of the time – less time for sleep.
Carnivores eat more nutritious food so can spend less time foraging
Carnivores generally sleep for longer.

42. 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 =

43. Meddis, (1975) - Predation theory
“Waste of time Hypothesis”
Sleep = avoid predators when most vulnerable
Most animals = darkness + hidden
Staying still with nothing better to do
Siegel (2008) being awake is more dangerous
Sleep is for energy conservation + avoiding danger
Best strategy for passing on genes = sleep for as long as you can get away with

44. Lions can do little else but sleep for up to 2 days after a large kill

45. Objectives – Lesson 4 Mini-test
To evaluate research on evolutionary theories of sleep
To Develop an essay plan to answer the likely exam question
psychlotron.org.uk

46. Evidence
Sleep patterns are affected by energy expenditure & availability
Animals generally sleep more when weather is cold and food is scarce (Berger & Phillips, 1995)
However, no direct correlation between physical work done and sleep duration in humans (e.g. Horne & Minard, 1985)
psychlotron.org.uk

47. Evidence
Comparative studies of different species generally support evolutionary view
Smaller animals tend to sleep more than larger (e.g. giraffe 1hr vs. bat 20hrs)
Carnivores sleep more than herbivores (e.g. lion 16hrs vs. buffalo 3hrs)
Some notable exceptions e.g. rabbit (small, herbivore) & human (much larger, omnivore) both sleep about 8hrs
psychlotron.org.uk

48. 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.

49. Test What is the purpose of sleep according to evolutionary theory?
Why do differences in the sleep patterns of species of animal support this?
What did Meddis claim about the purpose of sleep?
According to Webb why do carnivores sleep more than herbivores?

50. 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?

51. Problems
Many evolutionary significant factors could affect sleep patterns; theory doesn’t tell us which are important
Does a bat get so much sleep because it’s small or because it has few predators?
Why do animals with very different lifestyles have similar sleep patterns?
psychlotron.org.uk

52. Problems
Some features of sleep cannot be explained easily by the hibernation theory:
Why is sleep universal when in some species (e.g. dolphins) it would have been an advantage to get rid of it?
Why is sleep deprivation apparently fatal?
psychlotron.org.uk

53. 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)?

54. Horne
(1988) Core sleep consisting of SWS & REM is essential for normal brain functioning. Stages 1-3 NREM sleep are not essential. During core sleep the brain recovers & restores itself, but bodily restoration occurs during optional sleep & periods of relaxed wakefulness.

55. 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?

56. Task
Find one supporting and one opposing piece of evidence for each of the evolutionary purposes of sleep – use page 154 to 155 and write down your findings.

57. Test Explain why evolutionary theory contains a contradiction.
Why is REM sleep a problem when it comes to energy conservation?
Why can research on different species of animal sometimes be flawed?
What is a phylogenetic signal?