- Created by: ami riddell
- Created on: 27-01-10 17:40
Circadian Rhythm: the sleep-wake cycleThe suprachiasmitic nucleus (SCN) is in the hypothalamus, just above the optic chasm so it can gain input fairly directly from the eyes.Morgan (1995)Removed SCNs from hamsters, circadian rhythms disappeared.Transplanted SCNs from hamsters who had mutant circadian rhythms, found the hamsters
Silver et al (1996) if SCNs are transplanted into an animal whose SCN is removed, the animals receiving the transplants have restored rhythms.
A02:- SCN is endogenous pacemaker
- Ethics: PfH; humans and hamsters have same SCN? Human SCN maybe more complicated; hard to gen.
- Findings show a consistent effect removing and transplanting SCN: highly skilled neurosurgeon – hard to replicate/ test. Lab – controlled, C&E.receiving transplants took on the mutant rhythm.
Schochat et al (1997) Role of melotonin in circadian rhythms. 6 males spent 29 consecutive hours in a sleep lab. Spent 7 mins in every 20 lying down in a dark room trying to sleep. Blood samples taken every 20 mins to measure melotonin. A daily secretion of melotonin into the blood consistently preceded sleep-gate by 100-120 mins. Insomniacs find it easier to sleep when given melotonin 2 hours prior to sleep.
Melotonin is usually an endogenous pacemaker, but is a zeitgeber 2.
Sleep lab, specialist artificial environment/ informed consent/ PfH – stressful/ androcentric and small sample.
Study is biological, can generalise. Does not say melotonin causes sleep, just that it precedes it.
Helpful for insomniacs. The drug proves more likely that melotonin does cause sleep.
Michel Suffre: spent 2 months living in a dark cave, developed a 25 hour sleep-wake cycle.
- a pattern exists – biological clock?/ Natural light is the big exogenous zeitgeber and is necessary for 24hr cycle/ as a case study, can’t establish why this occurred or C&E/ individual differences.
Miles et al (1977) a man blind from birth. 24.9 circadian rhythm despite his alarm clocks. Only way to reset rhythm to 24 hrs was to use sedatives to help him sleep and stimulants to help him wake. This suggests light is v. important to keep 24hr rhythm.
Luce and Segal (1966) Arctic circle people sleep for 7hrsin summer despite sun at night.
A02:- shows that main E.Z. not always needed; some instances other zeitgebers (such as social customs) take over.
- E.Z. keep us in a synchronised cycle to maintain order. Nothing would function if we relied solely on E.P.
Infradian Rhythm: the menstrual cycle
The endogenous pacemakers are hormones: oestrogen and progesterone.
Women who lived in cave for 3 months with dim lighting: cycle shortened and sleep-wake cycle lengthened.A02:
- Light acts as an exogenous zeitgeber for the menstrual cycle
- Can’t generalise because study was on 1 woman – indiv. Diff. Artificial environment could change cycle.
- Strange results, no men so cycle should have been longer or stop – no chance of pregnancy.
Women who spend time together have synchronised cycles, possibly because of pheromones.
Women who work with men often have shorter cycles because of pheromones released by men.
Pheromones are exogenous zeitgebers
Makes evolutionary sense for pheromones to shorten cycle of women if they work with men because there’s more time to get pregnant. Do all men have this feature? (e.g. boys before puberty? old men? Etc)
Russell et al (1980)Control group and experimental group. Donor’s odour was collected from pads under arms; dissolved in alcohol to rid bacteria; placed on upper lip of Pp. After 5 months: 4/5 exp. Group had synchronised cycles.
More reliable study as: collected pheromones in a valid way, highly controlled study (C&E), had control group
Can generalise because its biological (cultures don’t matter) BUT some women might emit stronger/ more pheromones than others
Not all women affected: hormones more influential than Pher/ Pher more likely to coincide with similar cycle.
Evolutionary reason: Women’s menstrual cycles coincide so women have babies at same time so mothers can care for all babies
Ultradian RhythmThis would be our sleep cycle, there are 5 stages of sleep:
1) Stage 1 – person becomes relaxed and drowsy
2) Stage 2 – EEG waves become slower and larger; quite easy to be woken up in this stage
3) Sleep depends; EEg waves are slow and large
4) Stage 4 – a.k.a. SWS or ‘deep sleep’, body temp drops, growth hormone secreted now
5) Stage 5 – REM sleep, EEg indicates that brain is active.REM sleep decreases with age; as sleep progresses REM increases in quantity and stage 4 decreases and is gone by 2am.A person sleeps in this pattern of stages (most people have 5 cycle a night):cycle 1: 1,2,3,4,3,2,5; cycle 2: 2,3,4,3,2,5Muscles experience “Virtual paralysis” – twitches occur during REM therefore muscles are active.
Sleep Deprivation Studies
Stayed awake for 8 days; suffered from hallucinations, severe delusions and low body temp; consequences lasted for years and his mood was negatively affected for the long term.
Generalising is hard because of individual differences (sleep cycles vary), BUT we have biological similarities
Nat Obs study – low control, (C&E), indiv diff
- Short term is more affected, long term conseq. were more ambiguous. Other factors may have caused his bad mood.
Aged 17, stayed awake for 11 days. Suffered disorganised speech and blurred vision with small degree of paranoia. Afterwards, slept for 15hrs, recovered 70% of his stage 4 sleep and 50% of stage 5 sleep (REM).
Can’t generalise because of indiv diff and his age and gender might alter results BUT does provide a representative.
Stage 4 and 5 sleep are imperative in order to function and if lost can be mostly regained; possibly that stage 4 sleep more important than stage 5.
Lugaressi et al (1986)
Studied 56yr old man who had a genetic defect meaning he could never sleep due to damaged parts of brain; he eventually died.
There is something vital that our brains and bodies go through when we sleep, like growth or healing, without sleep we evidently can’t function.
Can’t see C&E because he could have had an undetectable illness, and one of the symptoms was no sleep.
Rechtschaffen et al (1983)
Rats on discs on water: EEG activity monitored to tell when they were about to fall asleep. When one rat was nearly asleep the disc rotated – had to stay awake otherwise it would fall in the water. The control rat sat on a rotating disc but stopped when it was falling asleep. The rat that was not allowed to sleep died in 33 days.
Suggests that the importance of sleep is universal to all animals
Unethical study – no protection from harm as the rats died.
Can’t generalise to humans: rats and humans might have different sleep cycles, humans might cope better.
Lab exp, highly controlled (C&E), but extraneous variables (disease? Stress?) not accounted for.
Partial sleep deprivation
Placed upturned flower pots in tanks of water. Cats had to sit on pots; when in NREM they stayed in pots, but in REm they lost muscle tone so fell in and woke up. Deprived of REM sleep. Cats soon died.
REM sleep is vital for rejuvenation of brain/ body and is clearly one of the crucial stages.
Cats and humans might rely on stages differently i.e. REM cycles less important for humans, can’t gen.
Unethical – PFH. Is study justified? Does the end justify the means?
Lab exp, C&E, highly controlled, but extraneous variables can’t be seen.
Webb and Bonnet (1978)
Deprived Pps of sleep gradually. Over 2 month period, they cut their sleep down to 4hrs a night with no apparent effects.
- Suggests that stages can be reduced, and in the first 2hrs we’ve had all stage 4 sleep anyway, implies stage 4 sleep is most important.
The Nature of Dreams
Who is dreamt about?
The dreamer is almost always personally involved.
Kahn et al (2000) found in 100 reports: 50% of characters were known to the dreamer/ About a third were generic characters (i.e. policemen)/ Less than 1 in 6 were unknown.
What do we dream about?
Hobson (2000) PET scans show that the brain regions most associated with emotions are active during REM sleep, the areas involved in decision making are not.
Martin (2002) Men dream about other men more than women dream about men – true across cultures and ages.
Content seems more negative than positive
Dreamer normally experiences an emotional detachment from the dream which is why we remain asleep unless the content is too disturbing
DurationDreams aren’t over in a flash, can last 20 mins so it’s hard to determine because its hard to measure.
REM and NREM dreamsDreams occur in both. REM is an active state accompanied by biological changes. REM dreams are usually weird stories and are like a narrative. NREM dreams feel like ordinary thinking.
Antrobus (1983) When judges rated 154 REM and NREM reports for their relative ‘dreaminess’, they correctly identified 93% of reports as either REM or NREM.
EEG scans have also indicated that there is a neurobiological difference between REM and NREM dreams.
Occurs during REM, have control of the dream. Dreams are vivid, tend to be pleasant and more straight-forward.
Hypnagogic and Hypnopompic Dreams Hypnagogic = sleep onset. Hypnopompic = between sleep and awake. These are very much like REM dreams but reduced. “Screen dreams” occur in hypnagogic dreams – Tetris plaed, many dreamed about it.
Risk of demand characteristics Self reported dreams – could be lying Ethical issues in exposure to computer games for a long timeA02: Why are dreams so difficult to study? Although various scales have been developed to help individuals record the content of their dreams, they’re still subjective.
Many studies carried out in sleep labs – artificial.
Recall might not be accurate
Research using brain scanners assume we only dream during REM sleep
Data is qualitative, so harder to interpret results as different people give different meanings to them so its harder to draw a conclusion
PET scanners are even more artificial than sleep labs.
Dement + Kleitman (1957)9 Pps; sleep labs; measured which stage of sleep they were in using EOG and EEG machines. When in REM, Pps were woken by a bell and then had to describe their dream into a microphone (immediate recall); they were woken up about 6 times a night, Eyes weren’t always in constant movement, spasms sometimes. Duration estimated length of dream by how many words Pps used to describe it/ asked Pp to estimate length Findings: Pps woken in REM sleep were dreaming 80% of time/ NREM = 7%. REM cycles lasted between 3-50 mins.
- Positive corre. Between no. of words used and length of REM sleep
- Distinguished differences between dreaming in REM and NREM
- Only used adults & ethnocentric so can’t generalise
- Causation can’t be inferred – possible the dream is causing REM
- Direction eyes move in can link to what you’re dreaming about i.e. eyes side to side = watching people play catch/ looking up = climbing a ladder
Restoration Theories & Ecological explanations of
Oswald (1980) – Sleep as an aid to physical recovery
Argued that SWS is needed for recovery processes and it restores depleted energy levels, eliminates waste products, repairs cells and recovers physical abilities. During SWS, a growth hormone from the pituitary gland is released and protein synthesis occurs, which would repair cell A02:
Sharpio et al (1981) Runners who had taken part in an ultra marathon covering 57miles slept and hr and a half longer on the 2 nights following the marathon + much longer time devoted to SWS.
Suggests sleep is needed to repair physical exhaustion and possibly that SWS has more healing properties than other stages. Not typical because these people are super fit.
Empson (1989) Noted that disruption of sleep in healthy people resulted in stiffness in back and muscle pain.
Supports Oswald as it suggests that SWS can cause physical problems as well as heal them.
Ryback and Lewis (1941) Healthy individuals who spent 6 weeks resting in bed showed no changes in their sleeping patterns.- Challenges Oswald – as there’s no psychological strain, lack of physical activity means that stage 4 sleep would be reduced, but there was no change.
Horne (1988) – Sleep as an aid to psychological recovery
Said sleep is not necessary for physical recovery, just rest without sleep. Instead, he said sleep was needed for psychological recovery – he distinguished between core sleep (SWS and REM sleep) and optional sleep (stages 1-3 sleep). He argued that core sleep is critical for normal brain functioning because during it the brain restores itself after the activities of the day.
A02:Horne and Minard (1985) exhausted their Pps with numerous activities (both mental and physical) and found people went to sleep faster but not longer.
- This doesn’t support either theory as according to both, their stages of sleep would have lasted longer, but they didn’t.
Sterne and Morgane (1974) REM sleep restores levels of neurotransmitters after the day’s mental activities. People on anti-depressants have less REM sleep, because the drugs increase their levels of neurotransmitters, so they do not need restoring by sleep.
- Supports Horne’s theory as core sleep (REM) is critical for normal brain functioning, but if they already have in excess they don’t need restoring therefore REM sleep is less important – drugs are replacing the need for REM sleep.
Oswald’s theory / Horne’s theory - Peter Tripp
Physical damage to his brain was irreversible. Could perform normally although he got cold gradually. Couldn’t be repaired psychologically and it damaged his mood.
Randy Gardner - Supports: made a full recovery from blurred vision and paranoia. Recovered from paranoia and disorganised speech.
Lugaressi et al - Eventually died as a result of exhaustion and lack of sleep because of damage to his brain cells. He could have only stayed in the 1st 3 stages of sleep and could not prepare psychologically.
Rechtschaffen et al - The rat who didn’t sleep died from not being able to sleep. Psychologically worn from being kept awake
Jouvet - Didn’t recover from the deprivation and had stage 4 sleep. Deprived of REM sleep
Webb and Bonnet
Can just be using stages 4 + 5 of sleep due to slow reduction of sleep. Supports both.
Meddis (1975) – sleep and predators/ food
Species sleep for different amounts of time, he explained this by considering an animal’s need for food and its method of obtaining it and its exposure to predators. Animals that cannot find a safe place to sleep, have high metabolic rates (need more food) and/or are at risk of predators don’t sleep much.
Short tailed shrews (burrow, high M rates) have 2 hrs sleep & prey animals sleep like sheep or deer sleep 3-4 hrs
Lions (no predators) sleep a lot
- Ground squirrel (burrow and slow metabolic rate) 14hrs
Webb (1982) – Hibernation Theory
Sleep plays an evolutional role because it conserves energy. Not conserving energy may decrease chances of survival. Sleeping when it is dark increases survival by decreasing risk of predation and death by accidents.
How long animals sleep only fits Meddis’ theory, doesn’t prove it.
Bottle nosed dolphins sleeps one hemisphere at a time, swaps after 30-60 minutes. Ties in with Webb’s theory because one half of the dolphin’s brain is conserving energy while sleeping.
Theories contradict each other: Meddis says it’s only sensible to sleep when there’s a safe haven; Webb says sleep decreases chances of being eaten. Meddis’ theory better.
Doesn’t really apply to humans as we have no predators
The ecological theories can’t explain why sleep hasn’t been predated out; both say sleep isn’t needed, just that it prevents things from happening. Lugaressi’s study suggests that sleep itself is vital to stay alive, as does Tripp’s.
Very reductionist theories: ignores psych theories with evidence to suggest its important. Suggests sleep is for evolutionary purposes and doesn’t serve any other purpose.
Neurobiological explanations of dreaming 1.
Function of dreaming is to get rid of useless information – “parasitic information” – stored in the brain as it used up valuable space in the cortex. It disrupts efficient organisation of memory needed as our cortex contains many networks that are interconnected; parasitic info means unwanted connections are made. Dreaming allows us to read out and destroy the parasitic info, so the dream is a by-product of reverse learning. A02: Hobson (1994) Levels of serotonin and noradrenalin are lower in REM sleep than NREM, this may explain why we forget dreams. Also, lower levels of them prevent us from paying attention, so its easier for the brain to misinterpret signals as if they came from the outside world rather than the brain = dreams.
Crick + Mitchison (1983) Cortex size. The only mammals not to have REM sleep are dolphins and spiny anteaters and both species have really big cortex’s.
theory doesn’t explain all types of dreams some dreams are meaningful foetus’ dream, or at least have REM sleep Are our brains likely to run out of space? Theory is not falsifiable – only looks at REM sleep
Positive points We usually forget our dreams
Dreams are often about what we’ve experienced during the day Dreams sometimes make sense. Very reductionist because it says dreaming is only about sifting out the rubbish we don’t need to remember because our brains are too small. We only use 16% of our brains; it says there’s no meaning to dreams and not all dreams make logical sense.
1. Activation-synthesis theory – Hobson and McCarl
Activation: During dreaming there are highlevels of activation in parts of the brain – vision, hearing, action and emotion. Little activation in areas related to smell or taste. Activation is random and does not relate to external stimuli. Synthesis: Humans search for meanings in things. We interpret the random activation as if it were produced by external stimuli, so we experience dreams. This is why dreams often make little sense – trying to synthesise random brain activation.
Hobson (1994) As before. Hobson (1988) Research on cats indicated that there is an apparent random firing of brain cells during REM sleep; the areas that are activated do link to visual perception and the control of movement.
many dream are coherent Some dreams are meaningful – this theory suggests none are. It cannot explain dreams that make sense and seem logical. Not all dreams occur in REM sleep
Animals have REM We do not dream about smell and taste
Less reductionist than other theories as explanation is complex, but only takes into account biological factors.
Endogenous Pacemakers, Exogenous Zeitgebers Essay Plan
1. Describe in detail endogenous pacemakers- suprachiasmatic nucleus (SCN) in the hypothalamus, SCN obtains information about light from the eye via the optic nerve, happens even when eyes are shut, as light penetrates the eyelids. If endogenous clock is running slowly, morning light automatically shifts the clock ahead, making the rhythm correct with the world outside again. SCN- pair of structures- one in each hemisphere of the brain, and each of these is divided into a ventral and dorsal SCN. Albus found that the ventral SCN is relatively quickly reset by external cues, but the dorsal SCN is much less affected by light and more resistant to being reset. SCN sends signals to the pineal gland making it produce melatonin at night, melatonin creates sleep because it inhibits the brain mechanisms that promote wakefulness.
1. Describe in detail exogenous zeitgebers- resetting the biological clock (entrainment). Light resets the SCN, also resets other oscillators located throughout the body as the protein CRY, part of the protein clock is light sensitive. Darlington- morning two proteins bind together CLOCK and CYCLE, once joined, CLK-CYC produce two more proteins, PERIOD and TIME (PER-TIM). PER-TIM makes CLK-CYC inactive, as PER-TIM increases CLK-CYC decreases and PER-TIM decreases as well (takes about 24 hours).
2. Critical Point 1: This explanation for the role of the Suprachiasmatic Nucleus is reliable. Morgan bred “mutant” hamsters so they had circadian rhythms of 20 hours instead of 24 hours and then transplanted their SCN’s into normal hamsters. He found that the normal hamster displayed the mutant rhythms. Therefore, this implies there is strong evidence to support the theory.
1. Critical Point 2: However, there is a methodological flaw to the majority of the studies carried out on this topic. This is they have been performed on non-human animals. As a result of this, it is difficult to generalise the results displayed by the non-human animals to humans. This is because human beings are far more complex creatures and also systems differ from animal to animal. Also there are serious ethical issues to consider when talking about non-human animals. Although, if we acknowledge that this research does have important applications for human behaviour, then the harm to animals might be considered acceptable as long as the key ethics of non-human animal research remain.
2. Critical Point 3: This explanation has a flaw. Folkard observed a women for 25 days living in a cave. He found that her temperature rhythm was a 24 hour one, but the sleep rhythm was a 30 hour one. Therefore, this implies that body’s separate oscillators can desynchronise which can lead to symptoms comparable to jet lag.
1. Critical Point 4: This theory has good evidence. Campell and Murphy found that if you shine a light on the back of the knee, then their circadian rhythms will shift. Consequently, this proves the theory useful as it demonstrates proof that light is the main exogenous zeitgeber.
2. Critical Point 5: There is a negative consequence from the research into the power of artificial lighting. Stevens implies that the exposure to artificial lighting disrupts circadian rhythms and therefore disrupts melatonin production. This could essentially explain why women in industrialised (and well-lit) societies are more likely to develop breast cancer. This is a positive application because it means that we can warn people about the dangers of having lots of lights on all the time.
3. Critical Point 6: There is a negative implication of having a biologically determined system. This is when it fails, it could cause many problems. Chicurel discovered one example of this is Familial Advanced Sleep-Phase Syndrome (FASPS) which has been linked with an inherited defect in one of the PER genes. It seems to cause sleep onset at around 7pm and spontaneous awakening at around 2am in affected family members, and so they have a great difficulty leading a normal life. Therefore this is evidence to support the theory of determinism as you cannot pick your genes.
1. Critical Point 5: There is a negative consequence from the research into the power of artificial lighting. Stevens implies that the exposure to artificial lighting disrupts circadian rhythms and therefore disrupts melatonin production. This could essentially explain why women in industrialised (and well-lit) societies are more likely to develop breast cancer. This is a positive application because it means that we can warn people about the dangers of having lots of lights on all the time.
2. Critical Point 6: There is a negative implication of having a biologically determined system. This is when it fails, it could cause many problems. Chicurel discovered one example of this is Familial Advanced Sleep-Phase Syndrome (FASPS) which has been linked with an inherited defect in one of the PER genes. It seems to cause sleep onset at around 7pm and spontaneous awakening at around 2am in affected family members, and so they have a great difficulty leading a normal life. Therefore this is evidence to support the theory of determinism as you cannot pick your genes.
Consequences of Disrupting Biological Rhythms Essay Plan
1. Describe in detail shift work and shift lag. Boivin found that night workers often experience a Circadian “trough” of decreased alertness during their shifts, this is between midnight, when Cortisol levels are lowest and 4am when core body temperature is at its lowest. Tilley and Wilson- daytime sleep is typically between one and two hours shorter than a nocturnal sleep period, and REM is particularly affected. Knutsson found individuals who worked shifts for more than 15 years were three times more likely to develop heart disease than non-shift workers. This could be because of direct effects of desynchronisation or indirect effects such as sleep disruption.
2. Outline briefly jet travel and jet lag. Recht- looked at US baseball results over a three year period. Teams that travelled from east to west won 44% of their games, unlike when travelling from west to east who only won 37%. The conclusion he drew from why this occurred is because east to west is phase delay so they wake up later then they are used to. Whereas, travelling from west to east is phase advance so they have to wake up and earlier then they are used to.
1. Critical Point 1: The effects described about disrupting biological rhythms have strong evidence. For instance Gold found that more problems happen where shifts alternate every few days. However, by finding out these results you can use it to improve shift work by making sure people do the same shift for a week before changing to a different time. Therefore, this research gives positive implications.
2. Critical Point 2: Most of the studies carried out are lab experiments so there is the issue of demand characteristics and whether the same results would apply in real life situations. Boivin and James used intermittent bright light in a field study of nurses, which confirmed the effectiveness of bright lighting to promote circadian rhythms. Therefore, this evidence shows that what was found in the lab experiments was true so it can be applied to real life cases.
1. Critical Point 3: There is another positive application for discovering about shift work and shift lag. Herxheimer and Petrie looked at 10 studies and found that where melatonin was taken near to bedtime it was remarkably effective. Consequently demonstrating that these effects do exist but they are treatable. However, there are individual differences to take into account when generalising results from different people, as well as volunteer bias in the sample.
2. Critical Point 4: Also, there are other ways to reduce the effects of shift work and jet lag. Fuller found that a period of fasting followed by eating on the new time schedule should help entrain biological rhythms. This is likely to be because some of our body clocks are reset by food intake. As a result of this, the results found from this research can be applied to real life making this research reliable and useful.
3. Critical Point 5: Finally, the other positive application for finding out about how shift work can disrupt biological rhythms is the introduction of forward-rotating shifts. Bambra claimed that they should follow the logical order of the day (phase delay). Therefore, they will be easier on the body and less damaging to worker health. As well as, rotating workers through shift changes more quickly, for instance every few days instead of weekly, is better for health and work-life balance.