Group quiz on questions from flipped work – no notes! 1.What is the main assumption of restoration theories of sleep? 2.What did Oswold argue was the purpose of REM and N-REM sleep? 3. What role does REM sleep have in memory? 4. What did Horne argue was the purpose of sleep? What did he distinguish a difference between?

Oswald suggested that NREM sleep (SWS) was vital for restoration of the body and REM sleep for restoration of the brain. Horne concluded that sleep did not necessarily involve body restoration but was essential for brain restoration, with major roles for REM and deep NREM Restoration theories Horne (1988) Oswald (1966) “Every stage of sleep is essential for restoration!” “No! Only SWS4 and REM are essential for restoration!”

Links to Specification Functions of sleep, including evolutionary and restoration explanations.

Past Exam Questions Outline and evaluate restoration explanations of the functions of sleep ( marks) Outline and evaluate one or more evolutionary explanations for the function of sleep ( marks) Outline and evaluate restoration explanations of the functions of sleep ( marks) Outline and evaluate one or more evolutionary explanations for the function of sleep ( marks)

Theories of the functions of sleep Restoration Theory

Why do we sleep? What does research into sleep deprivation suggest? What does research into sleep deprivation suggest?

Sleep Deprivation- Peter Tripp P20 Make notes and ground in pack

Randy Gardner- (1964) In 1965, an American student, Randy Gardner, aged 17, stayed awake for 260 hours (11 days). The effects of sleep deprivation on Gardner were less extreme than on Peter Tripp but still included moodiness, problems with concentration and memory, paranoia and hallucinations. After four days, he had the delusion that he was a famous American football player winning the Rose Bowl. He also mistook a street sign for a person. On the 11th day, he was asked to subtract seven repeatedly, starting from 100. He stopped when he got to and said he had forgotten what he was doing. He had no significant psychotic symptoms and appeared perfectly normal after a lengthy sleep.

Michael Cork- Fatal Familial Insomnia FFI: Inherited condition in which people sleep normally until middle age and then simply stop sleeping even though they want to. Death usually follows within two years and is associated with damage to the thalamus He slept fine all his life until one day, shortly after his 40th birthday in 1991, Corke began having trouble sleeping. In the following weeks, his sleeplessness grew worse and his health deteriorated. Eventually he was plagued by total insomnia - he could not sleep at all. Doctors were baffled by Corke's condition and he was diagnosed with Multiple Sclerosis, even though insomnia is not a symptom of MS. Nobody understood why he couldn't sleep, or why sleeping pills and barbiturates made it worse. Tragically, Michael Corke died in hospital after six months of total sleep deprivation.

Further Research evidence Each table will be given a research study or studies 1.What does this suggest about the Function of sleep? 2.Which explanation does this support? Why? You will have five minutes to ground these on the handout If you finish – imagine you are peer reviewing and add possible evaluation points at the bottom – link to theory!

Dement (1960) Read this content on page 21 in your pack Which function of sleep explanation does this study support? Why? Are there any relevant evaluation points to make for this study? (Add to the bottom of your handout)

Sharpio at al (1981)Runners in a marathon slept for about an hour more on the two nights following the race and SWS (stage 4) particularly increased. Empson (1989) Found that the disruption of stage 4 in healthy people resulted in stiffness in the back and muscle pain Horne and Minard (1985) Gave participants mentally exhausting tasks. Ps went to sleep quicker but not for longer.

Benington and Frank (2003) Conducted research with Rats Found that rats slept longer following completing learning tasks Suggests that sleep has a role in the function of Long term memory Crick and Mitchison proposed that during REM sleep unwanted memories are discarded, meaning we only have the memories we really need, making our brain more ‘efficient’.

Wider evaluation Usefulness of this theory – importance of sleep/problems that could arise from having sleep disorders especially insomnia. Use of animals to investigate effects of sleep deprivation Inconsistencies in sleep deprivation studies – may be due to individual differences. Variation in sleep patterns across species not accounted for – evolutionary better.

IDA – Restorative Functions of Sleep 1.The Biological approach- Strength/benefits 1.The Biological approach- Limiations/implications

Restorative functions of sleep “The restoration approach focuses on physiological processes in brain and body, a low level, simplistic and therefore reductionist explanation. It does not take into account evolutionary explanations and ecological factors such as predator- prey status which have been shown to influence sleeping patterns and great differences in sleep patterns across species. This means this explanation may be incomplete as it does not consider the complexity of sleep including, individual and cultural differences”

Theories of the functions of sleep Evolutionary (ecological) Theory

Evolutionary theory: Group quiz on questions from flipped work 1.What focus do the evolutionary theories have, as opposed to the restoration theories? 2.According to evolutionary theories what is the purpose of sleep? 3. What did Webb propose were the main functions of sleep? 4. What type of animal would sleep for longer and why? 5. Why might a predator sleep for longer than a prey animal? 6.What did Meddis propose was the purpose of sleep? Give an example?

On wallboards - Describe evolutionary theories of sleep. You must include all the points below in your answer Energy conservation (Webb ) Foraging requirements Predator avoidance ‘Waste of time’ You can use your notes from the flipped homework

1. Energy conservation (Webb ) Mammals expend a lot of energy just staying awake at a certain body temperature. We have a limited supply of energy so sleep acts as a way of reducing the amount of energy we use up each day as it is a period of ‘enforced inactivity’. Also, this can explain why some animals sleep more than others; smaller animals have a greater need for saving energy as their metabolism is higher, hence why they sleep more. Webb called this the ‘hibernation theory’ of sleep. 2. Foraging requirements This explanation can help us understand why some animals spend more time sleeping than others. Herbivores eat food which is low in nutrients, so in order to get the nutrients their bodies’ need they need to spend more time eating, and therefore spend less time sleeping. This could explain why some animals sleep much longer than others. 3. Predator avoidance ‘Predator avoidance’ is another way in which we can understand why some animals sleep more than others. If an animal is a predator it doesn’t have to worry about being attacked while it sleep, so it can sleep for long periods of time, conversely prey must spend as much time as they can afford to awake in order to avoid predators. 4. ‘Waste of time’ According to Meddis, sleep ensures that animals stay still and out of the way of predators when they have nothing better to do, so sleep is simply a way of wasting time. Seigel agrees with this view, saying that actually being awake and moving is more dangerous for prey as the animal is more likely to get injured.

Add to your pack if you haven’t already Evolutionary explanations suggest sleep is not vital, it serves an adaptive purpose rather than a restorative purpose.

Evidence Read the evidence and ground the research onto MWB’s.

PACKS AWAY! On MWB’s: List 3 pieces of evidence we have looked at. Swap your whiteboards. Look at your partners studies and choose a relevant and effective Ao3 point they could use and explain how this links to the theory.

IDA: Evolutionary approach So what? What are the weaknesses of using this approach to explain sleep?

Exam board comments on IDA: The Evolutionary Approach and understanding sleep Indicative issues, debates and approaches in the context of evolutionary explanations for the functions of sleep include the issue of generalising findings from animals to humans. Evolutionary approaches emphasise ecological niches for non-human animals, while humans have radically altered the nature of theirs over the last few centuries, so it is likely that conclusions derived from non-human animals would not apply to humans. This limits our understanding of the sleep of humans in contemporary society.

Wider evaluation Answer the questions in the pack.

Outline and evaluate evolutionary explanations of sleep (4 + 16) Many students wrote too much for this question. Popular explanations were energy conservation, predation, ‘waste of time’ and foraging patterns. Studies could usually be quoted, and some better answers focused on inconsistencies in results, eg metabolic rate and sleep time. Better responses discussed the possible separate functions of rapid eye movement (REM) sleep and slow wave sleep (SWS), and focused comparison with restoration explanations. Less successful students were sometimes diverted into the classic single case studies of sleep deprivation without making them relevant to the question. Effective IDA included the problems of extrapolating from animals to humans, given the nature of human social and cultural evolution. Less effective was a discussion of free will in relation to rabbit sleep patterns. Many answers referred to the sloth as being a problem for body weight/metabolic rate hypotheses of sleep time, as they are large and yet sleep for 20 hours a day. However, we have known for some years that in the wild the sloth sleeps far less than in captivity, about nine hours (Rattenborg et al., 2008).