Function of sleep

Starter – Lifespan and sleep Write a short email Use theory, research and evaluation Write a short email to Chris Thomson arguing for Bhasvic’s timetable to be changed Use at least one piece of evidence Can you include an IDA point?

Recap Draw a diagram representing the sleep wave at your sleep stage. Outline what happens at that stage of sleep.

Knowledge quiz: lifespan changes 1. What is the % of Rem sleep at each stage? Babies (50-60%) Older children (25%) Adolescents (20%) Adulthood (25%) 60’s (20%) 70/80’s (10%) 2. At what lifespan stage do you experience phase advance? People in the 60’s 3. At what lifespan stage do you experience phase delay? Adolescence 4. How many hours of sleep a night are needed at each stage? Babies (16h) Older children (12h) Adolescents (9-10h) Adulthood (8h)

Knowledge quiz: lifespan changes 5. When does our circadian rhythm become established? 6 months of age 6. At what two stages in our life are sleep disorders common? Older children and adulthood 7. At what stage in the lifespan is there no stage 3 or 4 sleep? Individual in their 90’s

Functions of sleep Aim of this session : The Specification Restoration explanations Evolutionary explanations Both include discussion of impact of sleep deprivation Aim of this session : Outline Restoration explanations of sleep Ground and evaluate research into the functions of sleep Evaluate Restoration explanations for the functions of sleep-

Restoration explanations Read the proposals by Oswald (1980) and Horne (1988) Summarise what they suggest about the function of sleep in two sentences

Example Restoration theories 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 (SWS or stage 4) Restoration theories “Every stage of sleep is essential for restoration!” “No! Only SWS4 and REM are essential for restoration!” Horne (1988) Oswald (1966)

Sleep Deprivation- Peter Tripp Make notes and ground in pack

Research activity What does this suggest about the Function of sleep? Which explanation does this support (Oswold? Horne? Both? Why?)

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 65... 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.

Dement (1960 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

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’.

MWB- List three pieces of evidence we have looked at today Swap your whiteboards Identify an appropriate Ao2 research evaluation point Explain why this is an evaluation point and remember to link to sleep

Application and Evaluation Prince’s death Currently there is a lot of discussion in the media around Prince’s death and the possible causes Read the article- Highlight and Annotate Use theory/evidence to support/challenge the claims that are made about the possible cause of his death Use further knowledge/evaluation (IDA?) to support/challenge the argument made

IDA – Restorative Functions of Sleep Group task Write an IDA on the wallboards based on the following points Reductionism- Strength/ benefits Reductionism- Limitations/ implications The Biological approach- Strength/benefits The Biological approach- Limiations/implications

IDA Template The restoration theory is Reductionist because ____________________________________ ____________________________ The is a strength of limitation of the approach as ____________________________________ ____________________________________ ____________________________________ This means ____________________________________ ____________________________________ ___________________________________

IDA Template The restoration explanations of sleep adopt a biological approach as it suggests………. This is useful/a problem because……. This means that…………..

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”

Plenary Write a question on the post it This can be of anything we have done in Bio Rhythms and sleep

Evolutionary theory Function of sleep.

Evolutionary Explanations Explain each with images and no packs (wallboards) 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.

Evolutionary Explanations Explain each with images and no packs (wallboards) 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.

Debating the evidence You will be given an explanation You will be given literature and evidence You must find evidence to support your explanation and your argument in the debate You will be marked on Your contribution of evidence Your link to the explanation Your use of evaluation points Your reflections and comparisons

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).

Sleep deprivation and Evaluation How do the sleep deprivation studies challenge the evolutionary explanations of sleep? Helpful hint : Fails to explain

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.

Plenary Watch the video Write down any “new” content / studies to add width/ breadth to your knowledge https://www.youtube.com/watch?v=3mufsteNrTI