SLEEP EEG TODAY Mummy, I Can’t Sleep! - PowerPoint Presentation

SLEEP EEG TODAY Mummy, I Can’t Sleep!
SLEEP EEG TODAY Mummy, I Can’t Sleep!

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What you need to Know Two theories about the function of sleep What happens during sleep and how this might relate to function Predictions Generated by each theory Evidence and evaluation points for each theory ID: 738217 Download Presentation


rem sleep amp theory sleep rem theory amp sws brain restoration org psychlotron evolutionary species patterns energy important hours evidence animals stages

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Mummy, I Can’t Sleep!Slide3

What you need to Know

Two theories about the function of sleep

What happens during sleep and how this might relate to function.Predictions Generated by each theoryEvidence and evaluation points for each theoryEvaluation using a possible THIRD theorySlide4


Slides 5 – 11 (plus text p148 & 154)

Mini-testTo know the stages of sleep (1-4 +REM) and brain activity related to each oneTo be clear about the difference between REM and NREM SleepTo be able to describe Restoration Theory of sleep with supporting evidence.Slide5

Qu. What are the sleep stages















Hours of sleep


EEG stagesSlide6

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 dropsAlpha & Theta wavesSleep spindles (stage 2)Brain waves are quite fastSlide9

Stages 3&4 Slow Wave Sleep

Deeper Sleep – harder to wake

Heart rate slows furtherTemperature keeps droppingSome slow Delta Waves (50%+ in stage4)Metabolic rate lowestGrowth hormone producedSlide10

REM Sleep

Paradoxical Sleep

Brain active - body paralysedFaster waves – like wakingIncrease in oxygen consumption, blood flow and neural firingRapid Eye MovementsHardest to wake fromSlide11

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 survivalSlide12

Objectives –

Slides 13- 27(and text p155)

Mini-testTo evaluate Restoration theory in two ways:Discussing supporting and opposing evidenceDiscussing the evidence that relates to the predictions of restoration theory

Restoration Theory

The function of sleep is to allow body to be repaired and restored

Oswald (1980)REM essential for brain recoverySWS 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 SWSKrueger et al (1985) found a link between lack of SWS and reduced immune functioning. Slide15

What is different about infant and old people sleep patterns?Slide16

Importance of REM sleep


In babies REM appears to be important for brain growthLength of REM in a species related to maturity at birthLess mature at birth = more REM neededCHECK – who needs more REM – a platypus or a dolphin?

Evaluate: Is this direct evidence?Slide17

Importance of REM sleep


Rogawki (1988)There is break in neurotransmitter releaseThis allows neurons to regain sensitivitySupport

MAOI’s increase levels of monoamines (


serotonin and dopamine)Side effect – REM is abolishedWhy? Increase in monoamines mean receptors don’t need revitalising So – no need for REM (Siegel 2003)Slide18

Importance of REM sleep


REM consolidates procedural memorySWS consolidates semantic memory and episodic memoryStickgold (2005)Evaluation – Relevant to Restoration Theory? How?Slide19

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?Slide20

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?Slide21

Restoration theory

Main predictions:

Deficits in functioning during sleep deprivationRebound following deprivationIncrease in REM during brain growth, reorganisation & repairIncrease in SWS during illness, recovery from injury

Restoration theory

Main predictions:

Increased Exercise – increased sleep:Shapiro (81) Supports – How?Horne & Minard (85) opposed – How?

Peter Trip VideoSlide24

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 DementMay have been getting MICROSLEEPSlide25


Generally, people catch up on sleep following deprivation

Not all lost sleep is reclaimedAbout 70% of lost SWS and about 50% of lost REM typically recoveredOnly REM and SWS sleep is necessary

Illness & injury

Sleep does increase during illness and recovery from injury

Total sleep time increases during illnessREM increases during recovery from brain injury, ECT & drug withdrawalSWS deprivation can cause physical symptoms


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?Slide28


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

Objectives – Slides 29- 39and text p154Slide29

Evolutionary/circadian rhythm model

Sleep’s purpose = increase the chances of survival



Ecological niche

Species sleep patterns are different due to….Slide30


Hrs of sleep/day

Giant Sloth

Tree Shrew

Cat, Hamster

Mouse, rat, squirrel


Humans, rabbit, pig

Cow, Goat, Elephant

Horse, Roe deer











mammals and birds sleep.

Qu. Do all animals sleep?

Qu. Can you explain these differences?Slide31

Qu. Do whales sleep?

Apparently soSlide32

Qu. Do fish sleep?

Apparently so

Fish, reptiles and amphibians have periods of ‘inactivity’Slide33

SWS and REM sleep patterns in mammalsSlide34

Evolutionary Theory of Sleep


Energy ConservationForaging RequirementsPredator Avoidance (“Waste of Time”)Slide35

Webb, (1982) –

Energy Conservation

Hibernation TheorySleep evolved to conserve energyPeriod of enforced inactivity - using less energy (Like hibernation)Important for animals with high metabolic ratesSlide36

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 foragingCarnivores generally sleep for longer.Slide37

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 = Slide38

Meddis, (1975) -

Predation theory

“Waste of time Hypothesis”Sleep = avoid predators when most vulnerableMost animals = darkness + hiddenStaying still with nothing better to doSiegel (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 withSlide39

Lions can do little else but sleep for up to 2 days after a large killSlide40

Objectives –

Slides 42-54and text p155

Mini-testTo evaluate research on evolutionary theories of sleepTo Develop an essay plan to answer the likely exam question


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)


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

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.Slide44


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?Slide45

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?Slide46


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?


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?


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)?Slide49


(1988) Core sleep consisting of SWS is essential for normal brain functioning. Stages 1-3 NREM and REM sleep are not essential. During core sleep the brain recovers & restores itself, but bodily restoration occurs during optional sleep & periods of relaxed wakefulness.Slide50


(1997) SWS (more dominant in the first 6 hours of sleep) is biologically essential.

In sleep labs participants deprived of sleep for 72 hours only needed 8 hours to restore powers of concentration. Most of the 8 hours is spent in SWS.People adapt to less sleep by sleeping more efficiently – going to sleep faster, entering deep sleep faster and waking less in nightSlide51


(1997) SWS (more dominant in the first 6 hours of sleep) is biologically essential.

EVALUATE HORNE’S METHOD AND FINDINGS – how convincing are his conclusions?Slide52

Horne (1999) - asks;


. What is the point of falling unconscious?Qu. Is sleep is purely restorative, why are there so many variations of sleep patterns across species?Slide53


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.Slide54


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?

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