Transcript sleep with pictures (LRA) 2012

SLEEP
Dement and Kleitman (1930’s)
Qu. How do we measure sleep?
Electro-encephalogram
Electro-oculogram
Electro-myogram
(Head)
(Eye)
(Neck)
EEG TODAY
Brain Waves and Sleep Stages
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. 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
 Cognitive model = Sleep is necessary for the
consolidation of memory and mental
functioning.
Restoration Theory
psychlotron.org.uk
The function of sleep is to allow body to
be repaired and restored
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?
Oswald
(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.
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.
Siegal (2003)
Some antidepressants which increase
levels of monoamines such as dopamine
and seratonin abolish REM sleep.
Why might this be?
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
psychlotron.org.uk
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
psychlotron.org.uk
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
psychlotron.org.uk
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
psychlotron.org.uk
Sleep does increase during illness and
recovery from injury
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?
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?
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
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 =
Lions can do little else but sleep for up to 2
x days after a large kill
Webb, (1982) - Hibernation theory
Sleep evolved to conserve energy
Hibernation necessary when food resource
are low.
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 generally sleep for longer.
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
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)
psychlotron.org.uk
Sleep patterns are affected by energy
expenditure & availability
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?
psychlotron.org.uk
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?
psychlotron.org.uk
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?