Transcript Introduction to Psychology

SLEEP
EEG TODAY
Mummy, I Can’t
Sleep!
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
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.
Qu. What are the sleep stages?
Awake
1
EEG stages
2
3
REM
4
0
1
2
3
4
5
Hours of sleep
6
7
Qu. How do we measure sleep?
Electro-encephalogram (Electrical Activity)
Electro-oculogram
(Eye Movement)
Electro-myogram
(Muscle tension)
Brain Waves and Sleep Stages
Stages 1 & 2
Relaxed state – easily woken
Heart rate slows & temperature drops
Alpha & Theta waves
Sleep spindles (stage 2)
Brain waves are quite fast
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
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
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
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
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Objectives – Lesson 2
Restoration Theory
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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
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.
What is different about infant and
old people sleep patterns?
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?
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)
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
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?
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?
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?
Restoration theory
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
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Main predictions:
Restoration theory
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Main predictions:
Increased Exercise – increased sleep:
Shapiro (81) Supports – How?
Horne & Minard (85) opposed – How?
Peter Trip Video
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
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.
Rebound
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
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Generally, people catch up on sleep
following deprivation
5yrs
REM
NREM
Age
Reduction in
sleep over
lifespan
Highest in
infants;
highest REM in
early years
Some changes
in adolescence
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24 hour period
Growth & reorganisation
Illness & injury
Total sleep time increases during illness
REM increases during recovery from brain
injury, ECT & drug withdrawal
SWS deprivation can cause physical
symptoms
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Sleep does increase during illness and
recovery from injury
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?
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%
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?
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
Evolutionary/circadian rhythm model
Sleep’s purpose = increase the chances of survival
Species sleep
patterns are
different due
to….
BRAIN
DEVELOPMENT
Ecological niche
BODY SIZE
Qu. Do all animals sleep?
Mammal
Giant Sloth
Tree Shrew
Cat, Hamster
Mouse, rat, squirrel
Hedgehog
Humans, rabbit, pig
Cow, Goat, Elephant
Horse, Roe deer
Hrs of
sleep/day
20
15
14
13
10
8
3
2
2
All mammals and
birds sleep.
Qu. Can you explain
these differences?
Qu. Do whales sleep?
Apparently so
Qu. Do fish sleep?
Apparently so
Fish, reptiles and
amphibians have
periods of
‘inactivity’
SWS and REM sleep patterns in mammals
Evolutionary Theory of Sleep
THREE KEY ASPECTS
Energy Conservation
Foraging Requirements
Predator Avoidance (“Waste of Time”)
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
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.
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 =
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
Lions can do little else but sleep
for up to 2 days after a large kill
Objectives – Lesson 4
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Mini-test
To evaluate research on evolutionary
theories of sleep
To Develop an essay plan to answer the
likely exam question
Evidence
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)
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Sleep patterns are affected by energy
expenditure & availability
Evidence
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
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Comparative studies of different species
generally support evolutionary view
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.
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?
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?
Problems
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?
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Many evolutionary significant factors
could affect sleep patterns; theory doesn’t
tell us which are important
Problems
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?
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Some features of sleep cannot be
explained easily by the hibernation
theory:
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)?
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.
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?
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.
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?