- Created by: katey.flude
- Created on: 27-05-16 15:27
Nature of Sleep: Lifespan Changes - AO1
- Babies: In babies, REM accounts for 50-60% of total sleep. Babies sleep for around 16 hours a day, but not in a continious block. Babies sleep cycle is shorter than 90 minutes.
- Children: REM accounts for 25% of total sleep. Parasomnia (sleep disorders) such as sleepwalking and night terrors are common at this age. The need for sleep decreases during this stage. At age 5 they sleep for approximately 12 hours a day.
- Adolescence: REM accounts for 20% of sleep. The need for sleep increases slightly from about 9 to 10 hours sleep. They experience phase delay this means they feel naturally more awake at night and have more difficulty getting up early.
- Adults: Adults typically sleep for 8 hours a night. Adults spend 25% of their sleep time in REM. Skeeo disorders are more likely at this stage.
- Older Adults: Daytime naps are more likely for people in their 60's. REM accounts for 10% for 10% of total sleep for people in their 70's/80's. No stage 3 or 4 sleep for people in their 90's.
Nature of Sleep: Lifespan Changes - AO2
- IDA: This links to the biological approach. This is because it shows how our biology can directly affect our patterns of sleep throughout our lifespan. For example it explains why sleep needs may change at various stages of our development. This enables us to construct a better understanding of how some groups may suffer as a result of enforced sleeping and walking schedules that go against their natural rhythms. This is important knowledge as we know a disturbance of the natural circadian rhythms can have a bad effect on their health.
- Breedlove et al: Suggest that the high level of REM sleep that happens before and after birth, helps the brain grow and helps it become more organised, as babies are learning so much. This supports the theory as it shows babies have long amounts of REM sleep.
- Wolfson and Carskadon: Surveyed 3000 American students and found they were getting on average 7.3 hours of sleep. A quarter of them were getting 6.5 hours or less. They found that those who achieved mostly A grades went to bed earlier and slept longer than those getting lower grades. This suggests that the more sleep you get, the better your cognition will be.
- Ancoli-Israel et al: Argued that older adults who are healthy rarely have sleep problems. They argue that poor sleep in the elderly is not a problem with ageing, but is causes by illness and medications to treat them are more prevalent in the elderly.
Nature of Sleep: Lifespan Changes - AO3
- Ancoli-Israel et al's research illustrates problems with establishing cause and effect as we can't say if poor health causes the problems or if it is a lack of sleep. However, it is problematic as it is a natural experiment which means that researchers did not have control over the variables, which could mean that the findings are innacurate.
- Webb: Found that participants data was consistent on different nights but it wasn't consistent across participants, even when participants were drawn from the same age range. It suggests that there are too many individual differences, which means that we can't generalise it to specific age groups as there are just too many differences.
- Other research has found that sixth forms giving teenagers longer time to sleep in the morning decreased the amounts of absence and seemed to enhance children's cognitive performance. However, this is socially sensitive as it could lead to disruption in the lives of people who work in education, as they may not beneift from this. However, there are lots of extraneous variables such as teenagers lifestyle in our cultures e.g. clubbing, which could be shown as different cultures don't have these problems. It is hard to establish a cause and effect because you can't isolate biological factors as this research is correlational.
Circadian Rhythms: AO1
- During any 24 hour period, there is a period of sleep and a period of wakefulness. This is one example of a circadian rhythm. The circadian rhythm is mostly controlled by internal ‘body clocks’ (endogenous pacemakers) but can also be influenced by external cues (exogenous zeitgebers). The main endogenous pacemaker for the circadian rhythm in mammals is the suprachiasmatic nucleus (SCN). The SCN is a cluster of neurones in the hypothalamus. The electrical activity of these neurons has an inbuilt or endogenous circadian rhythm which is maintained even when the SCN is isolated from the rest of the brain.
- The dominant zeitgeber in humans is light which enters into the retina and is transferred through the optical nerve to the SCN. This then stimulates the release of hormones such as cortisol and melatonin the pineal gland, thus maintaining our sleep-wake circadian cycle.
- Core body temperature- lowest at 4:30 am (36°c) and highest about 6pm (38°c), slight dip just after lunch- bi-daily. Hormones- lowest at midnight and peaks about 6am, makes you awake/alert, melatonin (stimulates sleep) and growth hormone both peak about midnight.
Circadian Rhythms: AO2
- IDA: Manipulating people's biological rhythms may be considered unethical. This is because it may have a deterimental effect on people and may cause long term damage. This means that most of the research is limited to animal and case studies. This represents a potential prblem for the internal and external validity. Therefore it may not be possible to draw firm conclusions as it cannot be generalised to real life situations and humans.
- Morgan: Removed SCNs from hamsters and found their circadian rhythms disappeared. He also transported SCNs from hamsters who had irregular circadiian rhythms and found that the hamsters took on circadian rhythms. This supports the theory as circadian rhythms by showing that the cycle is being controlled by endegenous pacemakers.
- Michel Siffre: Spent 2 months in a dark cave and developed a 25 hour sleep wake cycle.
- Miles et al: Wrote about a man who was blind from birth, he had a 24.9 hours circadian rhythm despite the fact that he was exposed to external cues such as radios and clocks. The only way to reset his circadian rhythm to 24 hours was through the use of sedatives to help him sleep.
- This all suggests that circadian rhythms are largely controlled by endogeneous pacemakers e.g sedatives and stimulants. It shows that the endogeneous pacemakers will create a rhythm but due to no light there will be a difference in the rhythm.
Circadian Rhythms: AO3
- It is reductionist to suggest that the sleep/wake cycle can be explained completely from endogeneous pacemakers, as it is likely that other biological factors are at play.
- Most of the studies are case studies which means the representativeness of the research is very low as we cannot generalise these findings to the wider population because the sample is so small.
- There is a problem with Morgan's study as humans are physiologically different from hamsters. Animal studies are useful to a degree as they help allow us to establish cause and effect relationships by conducting invasive research which would be unethical in humans.
- However, we can't generalise the findings to human beings. The SCN may not be as important in humans, because human sleep/wake cycle may be affected by light, or other exogenous zeitgebers such as alarm clocks.
- Therefore, we cannot draw firm conclusions from the research as we can't generalise most of the findings from these studies to the wider population.
- IDA: The greater understanding that the theory gives us of how the rhythm is controlled may lead to useful applications as it could help us deal with people who have circadian rhythm disorder, more effectively could also help us to minimise the unpleasant and harmful effects of shift workers and jet leg.
- Hibernation theory is one of a number evolutionary theories of sleep.
- Evolutionary theories suggest that sleep evolved because it allows an organism a greater chance of survival in a hostile environment.
- Specifically, Webb suggests that sleep has evolved because it forces the animal to conserve energy. In general, animals that conserve energy are more likely to survive than animals that do not. Therefore, the characteristic that helps them conserve energy is more likely to be passed onto the next generation.
- Sleep helps an animal to conserve energy in a number of way. For example: During sleep, behavioural activity stops, meaning less energy is spent on movement and metabolic rate and body temperature slow down, again, to save energy.
- According to Webb, an animals sleep patterns will be determined by the rate at which it loses heat, what it eats and the avaliability of food. By comparing the sleep patterns of different species at different times, it is possible to see whether these faactors appear to have an effect.
- IDA: The problem with using evolutionary theory to explain sleep is that it is impossible to test whether or not these processes actually resulted in the sleep patterns we observe today. We cannot go back in time to test this scientifically, so therefore the theory lacks scientific validity and amounts to no more than speculation. Its also difficult to identify a precise advantage.
- Rate of heat loss: The smaller an animal is, the faster it loses heat, so we would expect small animals to sleep more e.g.. voles sleep for 20/24 hours while giraffes can sleep only 1/24.
- Diet: An animal's diet determines its rate of energy intake and this determines how long it must spend each day searching for food. Carnivores eat large nutritious meals and thefore on't have to spend much of each day eating. Lions, therefore, can sleep as many as 18 hours a day. On the other hand, horses eat grass which contains little nutrition and this means they must eat massive amounts to stay alive which takes a long time, so they only sleep 3 hours in 24.
- The theory would predict that sleep time should increase when food is scarce because animals have greater need to conserve energy. Accordig to Berger and Phillips this is the case.
- This supports the theory as it shows that when there is little food around animals will sleep more, which could have happened due to evolution. However, thus research lacks scientific validity as we cannot tell if this is really due to evolution.
- Some animals with very different lifestyles seem to have similar sleeping patterns e.g. some animals and humans sleep for 8 hours a day and have very different diets and habitats, this would appear to pose a problem for the evolutionary theory as it cannot explain why this is true.
- This would decrease the reliability of the research as it could mean that research that is repeated could get very different results.
- Indus Dolphins: They have become blind because it is no longer needed, but its sonar system has improved. However, it hasn't stopped sleeping which we would expect it to do if sleeping was due to an adaptive process because of the evolutionary theory.
- Sleep deprivation studies: Show just how important sleep is and how we can't funtion normally without it, which would suggest that we didn't start sleeping due to evolution but actually because the body needs it to keep going.
- Therefore, this theory is not that strong as a lot of it is just speculation that we can't actually test and sleep can be explained through over theories like the restoration theory far easier.
Infradian Rhythms: AO1
- Menstural Cycle: The average cycle is 28 days long. Day 1 on the cycle is when the menstural period happens. On average, ovulation occurs on Day 14. It is controlled by the endocrine system (hormones) so it is under the control of endogenous pacemakers, although exogenous zeitgebers may also affect it, such as pheromones.
- Increasing amounts of oestrogem cause he lining of the womb to thicken, and around the 14th day of the cycle an egg is released from one of the ovaries. At this point, levels of progesterone also increase. If the egg is not fertilised within a two week period, levels of oestrogen and progesterone drop sharply. This causes the lining of the womb to shed, which is the menstural period. But some exogenous (external) factors do have an effect on the cycle.
- It is common that women who spend time together (e.g. girls in a boarding school) have synchronised menstural cycles. This is thought to be because of pheromones which are biochemicals, like hormones and neurotransmitters, but instead of being transmitted through the blood or brain cells, they are released into the air, and affect others. In humans, they can be released through sweat. Since pheromones can't be dectected there is some debate on whether they really do influence the cycle. It is also suggested that light has an effect, as if women are not in the light e.g. winter than their cycles may lengthen.
Infradian Rhythms: AO2
- IDA: The theory of why pheromones affect the menstrual cycle links to the evolutionary approach. This is because the theory presumes that the influence of pheromones has reproductive advantages. For example, if women ovulate more frequently around men, they are more likely to become pregnant. The problem with this approach is that it is impossible to test thus, this th theory lacks scientific validity and is merely speculation.
- Russell et al: Collected odour from sexually inactive women from pads placed under her arms. Once every 24 hours the pads were replaced. The pad was then rubbed on the upper lip of each participant and repeated for 5 months. At the end, four out of five women in the odour group has menstural cycles that synchronised to within a day or the odour donor. This supports the theory as it shows that pheromones seemed to change the women's menstrual cycles, however there could be lots of extraneous variables as conditions weren't controlled, so the women may be getting pheromones from other women.
- Some evolutionary psychologists have suggested that the synchronising of menstural cycles is to allow pregnancy to occur at the same time and therefore to allow babies to be born at the same time which would allow mothers to help look after each others' babies, affording the babies a greater chance of survival. This argument is flawed because just because you get pregnant at the same time, doesn't mean you will give birth at the same time.
Infradian Rhythms: AO3
- McClintock: Suggested that male pheromones may reset a woman's biological clock. This comes from the observation that women who work with men often experience a shortening of their menstrual cycle. This could make sense as having shorter cycles would mean that they would ovulate more often, making them more fertile but this may not be beneficial as it means you get pregnant faster which could mean that a man leaves a woman while they need them.
- Reinerg: Documented the case of a woman who spent 3 months in a cave with only dim lightning and found that her menstural cycle became shorter (25.7 days). It suggests that the menstura cycle is affected by light, as without it, this can shorten a woman's cycle.
- Further research does illustrate that light plays some role in the menstural cycle as research in Germanyshowed that the onset of menstruation was more likely to occur in the winter an menstruation is reached earlier by blind girls than sighted girls.
- This supports the theory as it shows the absence of light that happens in the winter or if you're blind does effect the menstural cycle and means that it can happen earlier.
- However, we can't establish a cause and effect as this is a natural study, so we ca't say whether extraneous variables such as weight could influence the onset of menstruation.
- This research has useful applications as if you were trying to get pregnant you could try more in the winter as you're cycle should be shorter.
Disrupting Biological Rhythms: Jet Lag - AO1
- Jet Lag: It seems that jet lag only occurs when flying from east to west or from west to east, but not from north to south. Therefore, it seems it is related to changing time zones and depends on a discrepancy between internal and external time.
- The symptoms of jet leg are: sleep disturbance - extreme sleepness/trouble sleeping; cognitive effects - poor performance on a task/fatigue and headaches, irritability, problems with digestion.
- Phase delay is when the circadian rhythm is lengthened by the need to go to sleep later and get up later. Phase advance is when the circadian rhythm is reduced in length by the need to go to sleep earlier and get up earlier.
- Flying east to west is most likely to cause phase advance and flying west to east is most likely to cause phase delay.
- Social jet lag refers to the discrepancy between your natural body clock and your social clock (the schedule you need to keep for your job and other social commitments). If you're relying an alarm clock to wake up every morning during the week, but sleeping in on weekends, thats a sign that you have social jet lag. The end result is that your body is shuttling back and forth between time zones each week and you're becoming increasingly sleep deprived. Social jet lag has the same consequences and symptoms as jet lag.
Disrupting Biological Rhythms: Jet Leg - AO2
- IDA: The theory has potentially useful applications as it could lead to recommendations which could minimise the negative effects of jet lag and social jet lag. This could mean taking naps when you land, and trying to wake up at similar times in the week and weekend to stop yourself from feeling the effects of sleep deprivation such as fatigue.
- Klein et al: Confirmed that flying west to east caused more jet lag than flying east to west by looking at flights from the UK to the US. They also found that one day per time zone crossed (each time zone is one hour) was needed for full recovery. This is likely as you can stay up in phase delay which is east to west, until it is the time zones turn to sleep. In phase advance which is west to east, it often means by the time you need to sleep, it is not appropriate in that time zone, so it will take you longer to adjust.
- To help with this you could take naps until you fall into your regular sleep pattern.
- Schwartz et al: Looked at American baseball games where teams travelled from the east to west coast, causing a time difference of 3 hours. West coast teams who travelled east had significantly fewer wins than the east coast. This suggests that its easier to trvale east to west due to phase delay which is easier to recover from. The study is low in validity as extraneous variables can effect the study, e.g other teams might be better. Good external validity as it is a real life situation. Social jet lag is quite a big problem as it happens to most people every weekend.
Disrupting Biological Rhythms: Shift Work - AO1
- Shift Work: It is work that is done at a pattern not in the usual 9-5 hours, such as pharmicutical engineer, nurse, pilot, factory worker.
- This disrupts the sleep wake cucle as they are asleep and awake at times that your body is not ready for.
- There are many worrying facts as industrial accidents such as Chernobyl and Bhopal all occurred between 1am and 4am and shift work was used at both plants.
- Most lorry accidents occur between 4am and 7am. It also takes about a week to adjust to a new shift.
- The negative effects of shift work are the increase of cardovascular disease; mood changes; gastro inrestenal problems; higher risk of work accidents; increase of disease and possible increased cancer risk.
- IDA: The explanation of shift work could potentially have useful applications as it could lead to recommendations which could minimise the negative effects of shift work e.g it could mean that shift work becomes less common because more people know about the negative effects of them.
Disrutping Biological Rhythms: Shift Work - AO2
- Blakemore: Looked at workers at a chemical plant who worked a three week schedule: first week was a night shift; next week was an evening shift and final week was a day shift. Lab animals who are subjected to this kind of roatating pattern of light and dark suffer from increased heart disease and a shorter life span. Shift pattern can be difficult to adjust to as it can lead to phase advance or delay depending on the hours worked, as you would have to change what time of day you sleep. We would expect the workers to become more tired and irritable and this could lead to more work accidents and medical problems for the workers. The animal study is useful to a degree because its the only way we could learn more in this field as we couldn't do this to humans. However, its unethical as this could lead to a shorter life span of the animals and we can't generalise the findings to humans.
- Czeisler et al: Proposed it would be better to rotate shifts forward in time so one begins with a day shift, progresses to an evening shift and then turns to a night shift. He tested this in the same chemical plant that Blakemore studied and found that they felt better and much less tired on the job. Management reported increased productivity and fewer errors. This is because it is easier for workers to stay up for a few extra hours than for them to sleep when they are not meant to, this ssures that they get some sort of normal sleep and minimises the negative effects of shift work.
Disrupting Biological Rhythms: Shift Work - AO3
- Fritschi: An Australian study of 1,000 women showed no link between brest cancer and shift work which has previously be suggested. Hansen et al: Studied 692 women from the Danish military found a link between the two. He found that working night shifts was associated with a 40% increase in the risk of breast cancer. The more night shifts worked, the greater the risk. He found that shift workers who described themselves as "morning" people (preferred to wake up early - phase advance) had a four times higher risk of breast cancer than those who worked in the day.
- Working at night in artificial light supresses melatonin levels, which can affect other hormones that influence breast cell growth. Breast cancer patients tend to have lower levels of melatonin than women without the disease. Genes may also play a role, since whether you're a morning or an evening person is partially determined by genetic makeup. It is harder for a morning person to adjust to hormonal and metabolic changes that come with working at night, increasing the risk of cancer. The studies may have different results as Hansen was looking at the Danish military, whereas Fritschi was looking at average Australian women. The validyt is high as both studies used a large sample which suggests that findings will be more accurate. However, the difference in results suggests that it is low in reliability which may suggest they're not actually that accurate. Shift work is more important as more people deal with it than jet leg.
Nature of Sleep: Stages - AO1
- An EEG machine is a non-invasive test that records electrical patterns in your brain. EEG waves are classified by frequency. Signals from the brain are called amplitude. There are two main classes of sleep: Slow Wave and REM.
- REM stands for Rapid Eye Movement. It is called this because it is characterised by the random movement of the eyes at this stage. In REM sleep there is increased respiration rate and increased brain activity. We do not act out our dreams so that we don't hurt ourselves or others. Dreaming does not only occur in REM sleep.
- Stage 1: Begins to fall asleep, heart beat slows, muscle tension reduced, Alpha waves are replaced by smaller slower activity, easily woken at this stage. Hypnogogic state.
- Stage 2: Patterns becomes synchronised. High amplitude, low freqency. Large, slow theta aves, interupted sleep spindles every 1 or 2 seconds.
- Stage 3: Heart rate continues to fall, amplitude increases. Long slow delta waves with some sleep spindles, less common. Sleep walking most likely at this stage.
- Stage 4: Body temperature and heart rate drops. Long slow delta waves. Hardest stage to wake up in. Human growth hormone released.
- Stage 5 (REM): We dream a lot at this stage. Rapid eye movement. Our muscles become paralyzed so that we don't act out our dreams.
Nature of Sleep: Stages - AO2
- IDA: The stages of sleep are biologically determined because they are caused entirely by brain waves. This is useful in terms of being able to research this area. The lack of environmental influence over sleep stages means that we can predict, with some confidence that they will be the same for everyone. This increases the reliability of the research and the emphasis on biological factors, along with brain imaging techniques means that we can study the nature of each stage of sleep in detaail which increases the scientific validity of the research.
- Sharpio et al: Disruption of Stage 4 sleep in healthy people resulted in stiffness in the back and muscle pain. This is useful because it shows that Stage 4 is important to restore the body and we could suggest to people that they may need to sleep longer.
- Dement: Found that people who are REM deprived were more irritable, aggressive and unable to concentrate on various tasks. This is useful because the knowledge of this precise stage of sleep can help us to understand how we can help people who may not get enough REM.
- IDA: This research could be considered socially sensitive. This is because greater understanding of the stages of sleep and their specific functions could be useful in helping us understand and treat certain conditions that could have their roots in the deprivation of specific key stages.
Nature of Sleep: Stages - AO3
- This could give greater understanding of the stages of sleep can be applied to beneift some groups of people - people such as alcoholics will have less REM sleep as alcohol suppresses this.
- The reseach into the stages of sleep does not allow us to assess the precise function of each stage as we do know what happens during this time but we don't know why it happens or has this function.
- This research does not mention anything about Stage 1 and 2. This demonstrates that our understanding in this area is still uncomplete.
- On the other hand, there are individual differences which need to be addressed meaning that not everybody follows the conclusions drawn from Dement and Kleitman’s research because the sleep stags apply to ‘average people’. Other research has indicated sleep changes with age and gender.
- For example the proposed sleep stages may not apply to people with more demanding lifestyles, such as a bodybuilder, because they might require more restorative sleep to match their bodily requirements. As a result, the conclusions drawn from the research into the nature of sleep might not apply to all people and treatments for sleep might not be effective for everyone.
Ultradian Rhythms: AO1
An ultradian rhythm is one that takes less than one day to complete, and an example is the sleep wake cycle. The sleep wake cycle consists of 5 main stages. The first four stages and non- REM sleep, while the last stage is the REM stage. Each cycle tends to go through all of the 5 stages, and lasts around 90 minutes. Stages 1 and 2 are called ‘light sleep’. Before we fall asleep our brains produce beta waves, and as sleepiness is induced, these waves become slower and are called alpha waves. Once we eventually fall asleep the waves slow down further and are called theta waves, which are accompanied by increased wave frequency and amplitude. Stages 3 and 4 are characterised by delta waves, and this stage is often called slow wave sleep, where growth hormone is produced and it is difficult to wake someone up. The last stage, which is called the REM stage, involves fast EEG activity, resembling the awake brain. It is also often called ‘paradoxical sleep’ since the brain and eyes are active, but the body is paralysed. The amount of Stage 3 & 4 sleep decreases with each cycle. The amount of REM sleep increases with each cycle.
Ultradian Rhythms: AO2
- Dement: His research was carried out in a sleep lab using specialised equipment which the sleeper is wired up to: EEGs were used to measure brain waves; EOGs were used to measure eye movements and EMGs were used to measure muscle movement. This allowed the researchers to distinguish the stages of sleep and to identify the cycles of sleep. The environment is controlled in a sleep lab and the participants may have to alter their diet before hand e.g. avoid caffeine. This is therefore objective as the researcher can't influence the brain activity as its not up to interupretation. It is reliable as it was done in lab conditions which means that the procedure would be easiter to do again.
- It has been shown that these factors can affect the ultradian rhythms: Repeatedly missing a night's sleep - this can result in the re-distrubution of sleep stages such as prolonged REM sleep; Alcohol - comprimises the quality of sleep, might increase insomnia; Caffeine - it can decrease the quantity of REM sleep and increse the number of awakenings and beta blockers - decreases the amount of REM sleep and slow wave sleep and increases daytime sleepiness.
- Wehr: Plunged young adults into darkness for 14 hours pet day. Whilst it took some time for their sleep to regulate, by the 4th week the participants had a regular pattern, they slept first for 3 to 5 hours and then woke for 1 or 2 hours before falling into a second three to five hour sleep.
Ultradian Rhythms: AO3
- Ekirch: Found that in Western society the idea of a first and second sleep had vanished by 1920. It seems that as night has become more of a time for social activity, the length of time that people wish to spend on rest has reduced, so the gap between the first and second sleep becomes a waste of time and people now attempt to sleep in one eight hour segment. Looked at many cultures over periods of time, which means it won't be culturally bias, however, using secondary research could lower the validity as we can't tell if the research is accurate.
- We can't say whether sleeping in these different segments would affect the cycle because not everyone actually has an 8 hour cycle, so it isn't true for everyone.
- Individual Differences: There are individual differences in the ultradian rhythm of sleep, both within the same person over time and from person to person. This means we do have to be cautious of over generalising about the contents of the sleep cycle.
- This research does have useful applications because it helps us to understand sleep better and can help us improve how we sleep and explains how it works. This means we can stop doing things that disrupt this cycle such as drinking alcohol or caffeine.
- Most research is done in sleep labs which could decrease external validity to a degree as they won't be done in real life settings, so they will lack ecological validity. However, no extraneous variables will effect the study, so the internal validity will be higher.
Restoration Theory: AO1
- Oswald: Proposed an early theory that REM sleep allows the restoration of and reorganisation of the nervous system. NREM sleep involves the restoration and repair of the body through release of growth hormone which is released from the pituitary gland in small bursts throughout the day, but released in larger amounts during stage 4 sleep. So stage 4 sleep is particularly necessary to the repair of the body and therefore plays a part in maintaining our physical health.
- Horne: Said that sleep was needed for psychological recovery. He also recognised that not all sleep is equally beneficial. He distinguished between core sleep (stage 4 and stage 5/REM) and optional sleep (stages 1-3). He argued that core sleep is critical for normal brain functioning because during these stages the brain restores itself after the activities of the day, replenishing levels of neurotransmitters that help to keep us functioning well psychologically. This means that without a sufficient amount of sleep, our psychological functioning would become impaired.
Restoration Theory: AO2
- IDA: The theory links to the biological approach. It shows us how our biology can directly affect our mood and behaviour e.g. impairment in physical and psychological functioning can be linked to the biological changes that happen in sleep. This enables us to construct a better understanding of the bases of some physical and psychological conditions. The emphasis on biology also allows us to pefrom more objective scientific research, making it more likely that we will be able to draw valid conclusions from the data.
- Sharpio et al: Found that those who ran an ultra marathon slept an hour and a half longer on the two nights after. There was more time devoted to Stage 4 sleep.
- Empson: Noted that the disruption of Stage 4 sleep in healthy people resulted in stiffness in the back and muscle pain.
- This supports the theory as it shows that people slept more after intense physical activity and if they didn't get enought Stage 4 sleep, then it seems their bodies didn't get restored enough.
- Dement: Compared participants who were deprived of REM sleep with those who were deprived of NREM sleep. He found the REM group were irritable, more aggressive and unavble to concentrate on various tasks.
- Borbely: Found REM deprived individuals made 31 attempts to re-enter REM on the first night of deprivation, 51 attempts on the second night and over 60 attempts on the third night.
Restoration Theory: AO3
- This supports the theory as it shows that those who lack REM sleep find it harder to psychologically function, which is shown as they couldn't concentrate on tasks.
- These studies all have good reliability as they have gotten similar results e.g. lack of REM causes physical and psychological issues.
- It is supported by patients who suffer from ‘fatal familial insomnia’; this prevents people from sleeping and leads to death within 2 years. Although these cases support restoration accounts, they are very rare and patients clearly have brain damage, making it difficult to generalise the findings.
- One may also criticize restorative explanations for being reductions as they fail to consider individual differences. If the function of sleep was restoration of mind and body then surely we would all sleep the recommended 8 hours a day; however, some people are known to sleep just 2 hours, thus the theory fails to explain these differences.
- The restoration theory also places too much emphasis on the biological approach which views the function of sleep as something that is determined. However, if we view things from a behavioural perspective, it is likely to see sleep as a product of social norms. For example, the belief that when it is dark we must sleep, and when it is light we wake up. Furthermore, if we convince ourselves that we need 8 hours sleep and we only get 5, it is likely we will feel tired due to these expectations. Thus, the restoration theory fails to consider these possible influences on sleep.
- Speilman and Glovinsky: Said that predisposing, precipitating and perpetuating factors can explain primary insomnia (insomnia that has no other known cause).
- Predisposing factors: Include a genetic vulnerability to insomnia which may be associated with the physiological state of hyperarousal which meants that the person experiencing a high level of arousal when they're awake or asleep. This means, that their metabolism is faster than that of good sleepers, their body temperature is slightly higher, their brain waves are faster, and they are thinking and speaking faster, this makes it harder for them to fall asleep.
- Precipitating factors: Include stress, which may be caused by a situation the person is currently experiencing, or environmental change that may temporarily make it difficult to get to sleep. This includes changing time zones. These factors are more likely to have a negative effect on sleep patterns if there is a predisposing factor present. Females suffer more from insomnia, possibly because of hormonal fluctuations. Older people also have more problems with insomnia, which may be down to increasing physical problems such as arthritis/diabetes.
- Perpetuating factors: Are factors that maintain the insomnia when the precipitating factors are no longer present. They include being tense when trying to go to sleep due to poor experiences of sleep in the past, or just the expectation that sleep will be difficult. These factors are key to chronic primary insomnia.
- IDA: This explanation is to a extent, biologically deterministic/reductionist. This is because it is explaining insomnia largely in terms of there being a biological factor towards insomnia. This could be considered socially sensitive as it implies that for some, insomnia is almost inevitable, therefore leading to a bad oulook to a suffering person. On the other hand, the theory does acknowledge the role of secondary, environmental factors on the individuals sleep pattern, therefore giving us a wider understanding of the complexity of factors that may underlie insomnia. It highlights the diffiulty in determining to what extent insomnia is determined by biological or environmental factors. The precise role of biological factors may be hard to establish. It also calls into question whether we can make a true distinction between primary and secondary insomnia, as it suggests the two are interlinked.
- Nofzinger et al: Found that the transition from being awake to being alseep is usually associated with a decrease in activity in the brain stem, thalamus and prefrontal cortex. Using PET scans, he showed that insomniacs experienced a smaller decline in such activity when going to sleep. They found elevated level of activity in the brains of insomniacs. This supports the theory as it shows that some perople have difficulty sleeping due to increased brain actibity which the theory suggests is a predisposed factor that some sleep walkers have.
- Ohayon and Roth: Interviewed 14,195 participants representative of the general populations of the UK, Italy, Portugal and Germany over the telephone about their psychiatric history and their sleep patterns. They found that people with insomnia were six times more likely to report a mental health proble, such as depression or anxiety, than perople without insomnia. This supports the precipitating factors part as it suggests that stress can cause insomnia and it has already been suggested that stress can cause mental disorders.
- This research had many different participants which makes it more representative and valid. There have been lots of supporting research for this theory which should make the theory more valid as if lots of studies agree it suggests that the findings are true.
- It is hard to draw strong conclusions from the research as it suggests that different things cause insomnia, however the research has quite high validity meaning findings should be truthful.
- The research supports the view that some people have biological predisposition towards insomnia to an extent as it shows that some predisposed factors do seem to effect whether you have insomnia, however other factors do seem to effect it as well.
Sleep Walking: AO1
- A diathesis stress model recognises that there are predisposing factors and environmental causes to a disorder (the stress). It is important to realise that sleepwalking occurs in SWS.
- This model of sleepwalking says that there is a genetic predisposition to sleep walkin, which is the diathesis; this genetic predisposition is likely to manifest itself in the form of incomplete arousal, in other words people's genes predispose them to be in this state, which is a state betweeen sleep and wakefulness. Sleepwalking occurs in SWS and typical EEG recordings taken during sleepwalking show delta waves typical of SWS plus higher frequency beta waves which are characteristic of an awake state. Hence it appears that sleepwalking occurs when the person in SWS is awakened but the arousal of the brain is incomplete so they still appear asleep.
- The stress (environmental) factors that make sleepwalking more likely to occur in those with a predisposition include sleep deprivation, drinking alcohol, fever and being a child. Children are thought to be more vulnerable because they have more SWS than adults and its thought that the mechanism that inhibits motor activity during SWS is not properly matured. Hormonal changes during puberty and menstruation may also be triggers for sleepwalking.
Sleep Walking: AO2
- IDA: This model suggests a biological basis to sleepwalking, whilst still taking into account environmental factors that may influence this behaviour. This can be considered useful as it leads to a less reductionist explanation of sleepwalking which could have important implicatons for the way we treat people who have the disorder. Its suggests that although there may be a genetic predisposition, there may be ways in which we can help those affected manage the impact of their biology. Therefore it is a more positive outlook for the individual than if we concentrated on the impact of biology alone, which would not necessarily lead to useful ways of managing the disorder.
- Broughton: Found that the prevalence of sleepwalking in first-degree relatives of those who are affected is at least 10 times higher than in the general population.
- Lecendreux et al: Found around 50% concordance in MZ twins compared to 10-15% in DZ.
- This supports the explanation as it suggests that sleepwaking may be affected by genetics as there is a link between them which is shown by how people who sleepwalk tend to have relatives with the same problem, which the explanation said would happen. However, we would have expected a 100% concordance rate between the MZ twins.
Sleep Walking: AO3
- Zadra et al: 40 patients were used, and observed during one normal night's sleep and then in a sleep lab for a second night where they were prevented from falling asleep, after 25 hours they were allowed to sleep. On the first night 50% of the sleep walkers showed signs of SW. After sleep deprivation this rose to 90% of the sleep walkers. Sleep deprivation doesn't lead to SW in normal individuals and therefore appears to be a characteristic of individuals who are genetically predisposed to sleep walking. This demonstrates it as one environmental facotes won't work without genetic factors, as it is shown in the study.
- There has been no successful treatment, but there have been ways that have fund how you may be able to lessen the impact through taking out some environmental factors.
- There have been cases where expert testimony is required in order to be able to decide whether a person was actually sleep walking or awake when they committed a crime. For example, Ken Parks killed his mother in law allegedly while sleep walking. He was acquitted of murder following the testimony of experts who said he was sleepwalking, so he was not in conscious control of his behaviour. This relates to applications of the research as it shows how important research into sleepwalking is and how it needs to be carefully and expertly looked into so that the research is valid and can be used in such cases.
- A fairly theory links narcolepsy, genes and the neurotransmitter, Hypocretin.
- It is also called orexin and regulates arousal, wakefulness and appetite. The brain contains very few cells that produce orexin: in a human brain about 10,000 to 20,000 neurons in the hypothamulus.
- Some genetic variations on chromosome 6 (known as the HLA complex) predispose an individual to narcolepsy. These variations increase the risk of an auto-immune response to neurons in the brain that produce the neurotransmitter hypocretin.
- Hence people with narcolepsy often have vastly reduced numbers of neurons in the brain that produce hypocretin, because the cells that produce it have been destroyed by auto-immune response.
- It is also possible that from some people the auto-immune response is not caused by genes but by a flu vaccination.
- IDA: This explanation of narcolepsy could be deemed reductionist because it suggests that the disorder is caused solely by biological factors, in this case a genetic variation leading to an auto-immune disease. It does not explain the environmental conditions needed for the disorder to develop and is therefore likely to be an oversimplified theory. On the other hand, it provides hope for people suffering from narcolepsy because it may eventually lead to an effective treatment or even a cure.
- Broughton: Reported that lifestyle adjustments, such as regulated sleep schedules and relaxing before bed, were more successful at treating the symptoms of narcolepsy than drugs.
- This decreases support for the theory as it suggests that lifestyle plays an important role in managing narcolepsy, which the theory overlooks.
- Mignot et al: Found that narcoleptic dogs had a defective hypocretin receptor 2 gene. This supports the theory as dogs with the gene all suffered from narcolepsy. The lack of function could have the same effect of destroying the cells in the hypothamulus.
- Montplaisir: Found abnormal numbers of hypocretinergic and dopaminergic neurons in the brainstems of 16 narcoleptic patients. This supports as it shows a link between abnormal hypocretin and narcolepsy, however, it suggests that dopamine might also effect narcolepsy, meaning it might not just be hypocretin that influences it.
- Montplaisir's sample of 16 is rather small which could mean that their findings are not truthful as it could just be a group of patients with strange neurons. All of the studies would be higher in objectivity as the researchers can't influence the studies results much. You can't generalise animal studies easily so Mignot et al's study was not actually very supportive.
- Dement: Found that mice who couldn't make hypocretin in their brains developed symptoms of narcolepsy e.g sleep attacks. This supports as it shows a link between hypocretin and narcolepsy as the mice lacked hypocretin.
- Nishino et al: Found a link between low levels of hypocretin in the human cerebrospinal fluid and narcopleptic symptoms. This supports as it shows how people with narcolepsy have low levels of hypocretin.
- The explanation cannot explain why certain people develop this disorder as there does not seem to be a strong genetic link.
- The explanation has lead to some drug therapies being developed which do seem to help people with the condition, however it is hard to evaluate how effective these treatments are.