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a cue given by the environment such as a change in light to change the body clock. Something that tells us the time.
External events that help regulate the biological rhythms - altered by external zeitgebers
Inherited mechanisms important for the regulation of biological rhythms particularily in the absence of external cues - Suprachiasmatic nucleus (SCN) and the pineal gland and melatonin
Infradian rhythms - Reinberg 1967
- Looked at the menstrual cycle of a woman who lived in a cave for 3 months with only dim light.
- Her menstrual cycle became much shorted whilst her sleep cycle became slightly longer (25 hours)
- This tells us that the menstrual and sleep cycle are affected by both the endo and exo factors as it continued to happen but changed due to the exogenous factors changing
- Evalution - lacks population validity as its only one person - individual difference
Russel et al (1980)
- Looked at the reasons why women sychronise their menstrual cycles, the theory is that pheromones pass on the messages.
- Took sweat from a doner woman, sterilised it and then places in on wipes below the noses of women
- The women soon synchronised to that of the woman doner - the exogenous pheromones allow them to do so
- The evolutionary theory - look after the children all at the same time
Russel et al 1980 evaluation
- only took a sample from one woman she might have massive amounts of pheromone in her sweat - so normally doesn't actually effect it
- Maybe the women only synchronised because it was placed right underneath their nose - lacks ecological validty
- Found that women's menstrual cycle can also be influenced by male pheromones.
- Women who work with men tend to have shorter menstrual cycles
- Evaluation: the work could be a masculine job - eg builder.
- Migration: - Gwinner (1986) kept wild birds exposing them to 12 hours of light and 12 hours of darkness and found they still showed migratory restlessness suggesting it is under endogenous control
- Hibernation: - Pengelly and Fischer (1957) artificially controlled squirrels exposed to light (12hrs light +12hrs darkness) and temperature but they still hibernated from October to April again suggesting endogenous regulations.
Circadian rhythm - sleep/wake cycle
Endogenous pacemaker - supra-chiasmatic nucleus tells the pineal gland then to turn serotonin into melatonin a hormone that makes you sleepy.
SCN control of the sleep/wake cycle.
- No melatonin during the day so you feel awake,
- 2pm: most awake body temp highest
- 10pm: SCN neural mechanism starts to synthesis of melatonin - melatonin then rises making us sleepy
- 2 am: deepest sleep - melatonin levels then decrease as it is used up
Michel Stiffre 1972
- Was studied for 7 months - asked to live undergroup in caves out of any contact with sunlight and without any cues to what time it is.
- monitored by computers, video cameras and had 24 hour link to the surface
- he settle down into regular cycle which was 25 hours not 24 as a result lost considerable amount of days and thought he has been their short than he actually had.
- Evaluation: it was only one individual lack population validity - might not all behave like that
- lacks ecological validty -exogenous zeitgebers will always influence us as in real life there not, not going to be there
- culture variation - he is french which is an industrialist country which may make his sleeping pattern different compared to other countries eg Africa
- Showed that if you removed the SCN altogether then the cycle stops.
- If you regrow it using foetal cells then the cycle returns.
Morgan et al (1995)
- He believed if the SCN determines the length of the sleepwake cycle then transplanting a mutant hamsters SCN into another hamster should transplant its cycle as well - it worked.
- Evaluation: hamsters are very different in terms of their brain structure and their sleep pattern which means you cannot generalise to humans which means its weak study and allows us to question whether endogenous factors are actually controlling the SCN in humans.
Miles et al 1977
- Studied a young man who had been blind since birth and had a 24.9 hour circadian rhythm despite being exposed to a number of zeitgebers such as tv and radio.
- Forced to use stimulants and sedatives to bring his daily rhythm back in line with the rest of the world - suggesting light is the dominant exogenous zeitgeber.
- Evaluation: only one person - could be different to everybody else and he was already disabled which could be an extranous variable- lacks population validity
- Biological and evolutionary theories
- reductionism/holism - extraneous variable - cognitive bias - training yourself to stay up (change in shifts)
- Freewill/determinism - an alarm or your choice to get up or go to bed -
- lack of real life application, gender bias and culture bias. (stiffre)
Stages of sleep:
- 2 different types of sleep - REM - rapid eye movement and NREM - not rapid eye movement
- 5 different stages:
- stage 1 (NREM): take up to 15 minutes, brain waves slow down; very light sleep
- Stage 2 (NREM): last 20mins; sleep spindles occur here; body temp and heart rate decreases
- Stage 3 (NREM): lasts 15mins; slow brain waves known as delta waves; transitional stage between light and deep sleep; heart rate falls further.
- Stage 4 (NREM): between 30-40mins; deepest sleep(difficult to wake up); growth hormone is released; metabolic rates is at its lowest; bed wetting and sleepwalking most likely to occur during this stage.
- Stage 5 (REM): last 10mins; EEG trace speeds up; brain oxygen and glucose demand increases; dreaming occurs in this stage; body is paralysed
More on stages of sleep
- Ultradian biol-rhythm which lasts about 90 minutes and is repeated 5/6 times a night
- Each stage has its own EEG trace (Electro-encephalographs) which records brain activity
- This is crucial for research - otherwise had to rely on self-report and visible eye movement.
- Evaluation: Ages differences in stages - babies need more REM
- Allows us to question whether dreaming is exclusive to REM sleep some studies have found dreaming happening in other stages.
Nature of sleep - Dement and Kleitman (1957)
observed that REM sleep is associated with a highly active brain whilst at the same time the muscles are effectively paralysed - paradoxical sleep a time where the brain is fully active but the body is not.
Nature of sleep - Jouvet (1967)
- He arranged flower pots unside down within a tank full of water with only a small part of the pot above water level.
- When the cats were put into the water they quickly got out the water on the exposed pot.
- When they eventually fell asleep in NREM they could support their body but in REM they couldnt as muscles became slack and slid into the water - waking them up
- This cycle repeated so stopped themseleve going into REM
- They started to display high level of stress and eventually died - sleep in essential
Evaluation of Jouvet
- tested on animals - not humans - cant generalise humans are more biologically complicated
- low ecological validity
- high stress levels could have been from the environment - trapped in a tank of water
Gulevich et al (1966)
- Randy Gardener ages 17 stayed awake for 11 days (264 hours) developed blurred speech with a combination of cognitive and perceptual faults; mild symptoms of paranoia
- Recovered after 18 hours of sleep just a quarter of the sleep he lost; most was REM
- This indicated REM is the most necessary and has important functions
- Peter trip DJ - stayed awake for 200 hours - publicity stunt; began to have delusions
- his personality seemed to alter after this sleep deprivation stunt
- Evaluation: Case study; individual difference
- was a publicity stunt may have tried to act more radical
Restoration Theory - Oswald
- Said that REM restores the brain and NREM restores the body
- Babies need more sleep because their brain and their bodies are growing therefore need more sleep than adults.
- Slow wave sleep -> release of growth hormone from pituitary gland -> protein synthesis stimulated -> tissue repair
Restoration Theory - Seigel
the more immature (smaller the baby is) the more sleep the baby needs. As we need it for growth
- REM by far is the most important for sleep deprevation
- When you have a lack of REM sleep you get an REM rebound which makes you have longer REM sleep the next night to recover
- Micro-sleep are minute catnaps or very small. Instants of sleep during awake periods which are so short lived that the person is not aware of them.
Restoration Theory studies
- Horne and Minard
- Turner et al 2007
- Born et al
- Cirelli and Tononi 2008
Did a study on marathon runners and found after a race they showed a decrease in REM sleep but did show more slow wave sleep.
Horne and Minard
Contradicts Shapiro because they found that after physical activity they didn't have more sleep overall.
Turner et all 2007
The effect on sleep on the cognitive abilities are that it reduces the working memory efficiency when there's a lack of it.
Born et al
Late REM sleep improves procedural memory
Cirelli and Tononi (2008)
found during the day you learn things but in sleep you organise these things you have learnt
Evolutionary explanations AO1
- Sleep occurs in all complex animals and therefore it is assumed that it has a survival advantage as genes for sleep would have been selected through evolution so they must help the animals survive.
- Focuses on the behavioral aspects of sleep. It uses the ethological approach to study animals in their natural habits. This is also called their ecological niche.
- Predator - prey status
- Hibernation theory
Predator - prey status
- Meddis stated that sleeping patterns depended on the predator-prey status.
- Prey animals with no safe place to sleep do not sleep much, for instance sheep sleep for about 2 hours a day.
- Animals not preyed upon sleep longer for example gorillas sleep about 14 hours a day. The animal’s food source is also important. Prey animals with a safe place to sleep, sleep longer as they can conserve energy, as they are vulnerable when they look for food.
- Predators like lions are carnivores and only need to eat once or twice a day and can sleep for about 14 hours to conserve energy.
- Some prey animals need to eat all day to survive and so sleep little.
AO2 - Predator-Prey status
- It is hard to look at all of these variables individually and it is difficult to know which posed the greatest selection pressure for sleep which could either be sleeping little because you need to eat all the time, or because you are a prey animal.
- Another argument against Meddis’ proposal is if safety was the only consideration, would be more effective to stay awake and alert, but quiet, than to fall asleep.
Allison & Cicchetti’s (1976)
study of 39 animal different species, prey animals generally sleep less than predators
Lesku et al. (2006)
States prey animals are herbivores and need long periods awake to locate and eat food.
Hibernation Theory AO1
- This is the theory that animals sleep to conserve energy.
- For instance mice sleep most of the day and they have a high basal metabolic rate so they would conserve energy as sleep is a time of relative inactivity when animals conserve energy resources.
- So small animals sleep more in order to conserve energy
Hibernation Theory AO2
- Clearer evidence supporting the hibernation/ energy conservation approach.
- This is supported by the finding of a positive correlation between basal metabolic rate (rate at which body burns up energy) and amount of sleep although this does not allow causality to be inferred.
- Small animals have higher BMR than larger animals so sleep more.
- So sleep would be more beneficial for small animals, although only NREM represents energy conservation as body’s processes slow down. In REM, energy consumption is only slightly less than when awake.
IDA Hibernation theory.
- Holistic - because takes the whole animal and its lifestyle into account (a variety of ecological and physiological variables that might influence sleep patterns).
- Freewill - humans can choose where they sleep, animals are governed more by instinct and their position in the food chain.
Life Span changes in Sleep
The older we get the less REM sleep we need this is because we grow in our sleep - confirmed y babies needing a lot of sleep (newborn baby REM sleep 8 - 90 year REM sleep 1)
Life Span changes in sleep studies
- Van cauter et al (2000)
- Foleyefal (2007)
- Ancoli-Israel (2008)
Van cauter et al 2000
- sampled 149 healthy adult males between 16 and 83 for 14 years
- They found that there is a reduction in slow wave sleep between the ages of 16 and 25 and 35 and 50
- Since growth/ repair hormones are secreted during slow-wave sleep this may have been a cause of loss of muscle - mass, reduced excerise and tendency for weight gain in these ages >45 years
- All stages of sleep decline with age.
- There has been found to be an increase of daytime napping in older adults and this has positively correlated with depression
surveyed 2000 women and found that normal sleep with no perceived sleep problems was linked to healthy aging older women who slept well were less likely to suffer from mood, attention or memory problems and were less likely to have physically problems such as coronney heart disease or diabetes.
- Free will - lots of extranous variables such as in van cauter et al the reason why men gained weight and lost muscle mass may be because of personal choice
- Its deterministic because we cant choose whether we sleep well or not
Explanations of sleep disorders:
- Sleepwalking (somnambulism)
- Affects 10% of the population. It involves problems falling asleep, maintaining sleep and reductions in sleep quality so sleep is non-restorative.
- Two types: - primary and secondary
Primary and Secondary insomnia
- Primary: - chronic insomnia occurring in the absence of any psychological or physical condition that might explain the disorder (a disorder in its own right)
- Secondary: Chronic insomnia that can be explained by a pre-extisting psychological or physical (medical) conditioning (caused by another disorder) could also be a result of sleepover walkng or sleep apnea.
- Differences: PI treat the insomnia
- SI treat the underlying cause.
- BUT not always clear if insomnia is just a symptom of the main cause or primary.
Explanations of insomnia
- Other sleep disorders - sleep apnoea, (abnormal pauses in breathing or instances of abnormally low breathing, during sleep), sleepwalking, snoring or teeth grinding can lead to insomnia.
- Medical conditions (e.g. heart failure)
- Drugs such as amphetamines, alcohol and hypotics affect brain neurotransmitters and probably lead to insomnia by disrupting the control of our complex sleep systems
- Age - older people are more likely to get insomnia due to problems such as arthritis or diabetes
Biological AO1 - insomnia
- Refers to common observation that some people are aroused, alert and functioning well in the morning and some people in evenings (some individuals are intermediate types and function well all day)
- Difference between extreme morning types (MT) and evening types (ET) is genetic and based on biological circadian rhythms of sleep and waking
- These characteristics are stable over time and represent a distinctively personality trait - controlled by endogenous pacemakers due to genetics
Biological AO2 - Insomnia
- Research shows MT - circadian rhythm is 2 hours of ET
- Lots of research supports chromosomes that effects endogenous pacemakers are genetically determined
- Deavilleers et al 2005
Deavilleers et al 2005
- found 73% primarily insomniacs reported a family history of insomnia.
- 24% in non-insomniacs -suggests a genetic component to the condition
Cognitive A01 insomnia
- associated with anxiety
- Clinical anxiety - we know anxiety can be a cause of secondary insomnia
- Associated with high level of physiological arousal acts against a tendency to sleep so more likely to suffer with insomnia
- Clinical anxiety and depression are major causes of insomnia and even in general population a tendency towards anxiety makes insomnia more likely.
Cognitive AO2 - insomnia
- Cognitive treatments are most effective - such as muscle relaxation and CBT
- Also supported by twin studies showing high levels of sleep disturbances (most insomnia) are associated with high levels of neuroticism a personality trait that is significantly correlated with anxiety
- Vahlera et al (2007)
Vahlera et al (2007)
Vulnerability to sleep disorders following traumatic life events such as divorce is highly correlated with the personality trait of anxiety
- Reductionist - a holistic approach may be needed
- Nature-nuture - Brain mechanisms V environmental factors
- May affect 10% of the population at some point in their lives
- Around 30% 5-12years may have episodes of sleepwalking but only occurs regularly in 1-5%
- Tends to run in families - genetic involvement
- The person typically has their eyes open but described as a glazed or soaring in appearance
- Typical behavior is moving around normally or just in the bed room
- However some people have been known to drive cars and ride horses - Ebrahim and Fenwick (2008)
- Tends to occur in stage 3+4 and therefore earlier at night since there is slow waves (less likely to happen in REM as muscles are effectively paralysed
Biological Explanations AO1 - Sleepwalking
- Tend to run in familes - led to assumption there maybe a biological (genetic) basis
- Some research supports this - Bassetti (2002)
- found 50% sleepwalkers has a specific gene which is only found in 24% non-sleepwalkers
- suggests genes may dictate the degree of vulnerability to sleepwalking
Biological Explanations AO2 - Sleepwalking
- But there is no clear biological explanation beyond the relationship with NREM
- Lack of reliability of research suggesting a genetic link as many other studies have found NO relationship
Psychodynamic Explanations AO1 - Sleepwalking
- It has been suggested that sleep walking represents a desire to sleep where the individuals slept as a child (however this doesnt explain the wide range of activities carried out)
- An explanation based of Fraud work suggest that we are working through unconscious anxieties during our dreams moving from REM to NREM prevents this so unconscious instinctual energies spill into NREM and are channeled into motor activities - Sleepwalking
Psychodynamic Explanations AO2 - Sleepwalking
As with most psychodynamic ideas, this explanation is impossible to test scientifically because it uses no empirical methods so unable to prove causality
General AO2 - sleepwalking(SW)
- Gender differences - boys suffer more than girls - limits generalisability from one gender to another gender
- Pilon et al (2008) have suggested that its more likely to occur if you are fatigue and had a previous lack of sleep. Other triggas are stress, alcohol and other drugs
- reinforced by Plazzi et al (2005) found that various factors appear to increase the likelihood of SW e.g sleep deprivation, alcohol, having a fever, stress, hormonal changes in puberty and menstruation can also be triggers
IDA - sleepwalking
- Is psychology a science? - subjective based on ideas of fraud- out of date - not falsifiable nor empirical
- No medical treatmenet has yet been devised to combat SW. The disorder incurs serious accidents and distressing incidents (sexsomia) - treatment is essential
- Randomly falling asleep - when you least expect it
- Only effects between 0.02% and 0.0005% of the western population
- It often occurs with cataplexy (sleep hallucinations) - not at the same though
- 4 major symptoms: - extreme daytime sleepiness
- episodes of cataplexy
- hypagoric hallucinations
- Sleep paralysis
- -> only 50% of sufferers show all four symptoms but have cataplexy and at least one other symptom
Biological Explanation AO1
- Since narcolepsy tend to co-occur with the above symptoms they may be a problem with the regulations of REM
- Since your body is paralysed and you dream in this stage
Biological Explanation AO2
- There is strong research support evidence suggesting this is the correct explanation of narcolepsy
- Vogel (1960)
- Nishino et al (2000)
- Thannickal et al (2000)
- However the overall research is weak - research has shown it might have something to do with the brain structure
found that REM is more likely to occur at the onset of sleep in people with narcolepsy in contract to normal people where they have REM at the end of their sleep cycle
Nishino et all (2000)
found a link between hypocretin and narcolepsy in humans
Thannickal et al (2000)
shpwed an 85-95% reduction in hypocretin neurons in people with narcolepsy BUT measuring these neurotransmitters is hard
Biological explanations (gene defect) AO1:
- A gene may be responsible for narcolepsy - shown in dogs
- The gene is responisible for regulating brain receptors for oxexin (a neurochemical that regulates arousal, wakefullness and appetite sometimes called the hypocretin)
- Without recpetors orexin can not function - lack of orexin/ its receptors may be the cause of narcolepsy in humans
Biological explanations (gene defect) AO2:
- Lin et al (1999) showed that dogs and mice with narcolepsy has a genetic mutant on chromosome IZ that lowers the production of hypercretin (which is a neurotransmitter that blocks messages about being awake and controls the REM)
- Supported by other animal studies suggesting we can generalise these findings to other species - however maybe not to humans as humans have very complex brain structures
- Nishino et al (2000) found 25-31% concordance rate for MZ twins with narcolepsy and a 1-2% rate in first order relatives - BUT the condition is not entirely inherit and therefore environmental factors must also be important
- Suggest psychology is a science - objective and empircal - counting neurons
- No effective treatment exists so the explanation cannot be truely correct otherwise it would be treatable - most stimulants deal with day time tiredness - palliative nor curative