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? 1 2 3 4 5 6 7 Awake Hours of sleep REM EEG stages

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

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

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

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 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

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

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 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

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

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

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 BODY SIZE Ecological niche

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?

Qu. Do whales sleep? Apparently so

Fish, reptiles and amphibians have periods of ‘inactivity’ 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 Mini-test To evaluate research on evolutionary theories of sleep To Develop an essay plan to answer the likely exam question psychlotron.org.uk

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

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

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 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

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

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?