Biological Rhythms

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  • Created on: 04-05-15 11:40

Biological Rhythms

Key words

  • Biological rhythms: regular patterns of physiological, behavioral or cognitive activity. They are usually broken into circadian, ultraradian and infaradian
  • Circadian rhythms: biological rhythms with a cycle length of 24 hours –sleep/wake cycle and body temperature control
  •  Infradian rhythms: biological rhythms with a cycle of more than 24 hours –menstrual cycle/ hibernation
  •  Ultradian  rhytms: biological rhythms that have more than one cycle in 24 hours – alternation between slow-wave sleep and REM
  •  Zeitgebers: external stimuli important in the accurate control of biological rhythms E.G light/ temperature/social cues
  • Endogenous pacemakers: internal ‘body clock’ that regulate biorhythms e.g. suprachiasmatic nucleus and pineal gland. It is likely that the activity of these pacemakers is innate
  •  Diurnal: animals that are awake and active during the day and sleep/rest in the evening
  •  Seasonal effective disorder: a form of depression that in some people repeatedly occurs during the winter months.
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How are biological rhythms controlled?

  • Controlled by environmental factors such as light/temperature/food availability – Exogenous/ external zeitgebers
  • However it may not be that simple as when there is an absence of exogenous zeitgebers biological rhythms are still maintained suggesting an in built / internal mechanism e.g. algae kept in lab conditions still burrow into the sand and emerge at times in tune with tidal flow at their home beach
  • Internal clocks are known as endogenous pacemakers

 

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Different types if biological rhythm

1.     Circadian Rhythms

  • Occur over 24 hours
  • Sleep-waking cycle involves period of 24 hours
  • Nocturnal animals are awake ta night and sleep during the day
  • Diurnal animals sleep at night and are active during the day – makes sense for the body’s physiological processes to be in tune with the natural sleep pattern so that during times of activity  (wake) body temperature is higher increasing metabolic activity and energy expenditure and vice versa for times of rest
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       2.  Infradian Rhythm

  •  Periodicity of more than one day e.g. the menstrual cycle and hibernation.
  • Menstrual cycle controlled by endogenous pacemakers but can be sensitive to external zeitgebers – menstrual cycles syncing up (anecdotal reports) – Russell,Switz an Thompson(1980) found that if sweat from one woman was rubbed on to the lips of another woman eventually the cycle would sync with that of the donor this is due to the influence of the external zeitgebers of pheromones.
  • Seasonal Affective disorder (SAD) form of depression that regularly affects vulnerable people in winter months-qualifies as infradian rhythm-people with SAD become depressed in the winter and tend to eat less and sleep more
  • Brief exposure to light first thing in the morning can be effective against SAD – the effect of light suppresses the sleep chemical melatoni

3.  Ultradian Rhythms

Less than a day’s length- human pattern of sleep, during a nights sleep we move through different stages of sleep- light slow wave to deep slow wave then back to light slow wave and then into rapid eye movement sleep and it takes 90 minutes on average

 

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Key words:

·       Melatonin: hormone secreted by the pineal gland- light reduces the level of melatonin and dark increases the level of melatonin

·       REM sleep: characterized by desynchronized EEG patterns, rapid eye movements and paralysis of the skeletal muscles, associated with dreaming

·       Suprachiasmatic nucleus: group of neurons in the hypothalamus. Have their own regular activity. Most important endogenous pacemaker and in turn controls the pineal gland and release of melatonin

·       Pineal gland:small structure in the brain that secretes melatonin

 Endogenous pacemakers and exogenous zeitgebers

·       Endogenous pacemakers are internal or in built body clocks. As regular rhythms of activity can be recorded in developing human embryos its is likely that these are in built

·       Exogenous zeitgebers –environment stimuli the most important being light

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Light, endogenous pacemakers and sleep

  • The SCN in the hypothalamus has an inbuilt endogenous circadian rhythm of electrical activity. Pattern is still maintained when the SNC is isolated from the rest of the brain showing that is truly is endogenous.
  • A direct pathway links the SCN to the retina of the eye. The retina is where light impulses are received and converted into nerve impulses, this pathway would allow light to regulate the SCN
  • the next stage in the the system is a pathway connecting the SCN to the pineal gland.
  • The pathway allows the SCN to control the manufacture and release of melatonin
  •  Abraham et al (2000(found that injections of melatonin produce sleep in sparrows
  • Binkley (1979) found that chickens wake up at dawn as melatonin levels fall
  •    **continuation of bio rhythms in the absence of external zeitgebers  can be explained by the endogenous rhythmic activity of the neurons in the SCN and pineal gland.The fact that the SCN can be directly affected by light mean that the endogenous pacmekaer ( SCN and pineal gland) can be perfectly synchronized with light and dark phases of the outside world
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Stephan and Zucker (1972): Investigated the effects of damage to the SCN on circadian rhythms

  •   Rats housed in a lab with 12 hours light then 12 hours dark show circadian rhythms of sleeping and drinking activity. Drink more and are more active during light periods
  • Compared group with damage to SCN with group of normal controls
  •  Damage to the SCN eliminated the normal circadian rhythm
  •  Concluded that the SCN is one of the key pacemakers

Evaluation: Damaged pother parts of the hypothalamus to show that this did not affect circadian rhythms\Surgical procedure was very difficult and only 11/25 survived therefore it is possible the severity of the op may have altered behavior

  • The use of controlled lesions in the brain confirmed the role of the SCN and suggested this was not a major factor in the study
  • Use of rats- cant be generalized to humans although pacemakers may be very similar/Ethical issue of use of animals – large amount of stress unto the animal / death for many-unlikely that such studies would be permitted today
  • Zucker,Boshes and Dark (1983) found similar results in the destruction of the SCN in ground squirrel
  •  Rusak and Zucker (1975) demonstrated that the circadian rhythm of testosterone release in male hamsters was eliminated due to SCN damage
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Siffre (1975) French geologist spent 6 months in an underground cave in Texas

No natural light- absence of critical zeitgeber bio rhythms will become free running.Cave artificially lit and he had a phone when he could ask for the lights to be switched on or off when he slept or awoke. He could eat and sleep when he wanted to

Findings: Sleep-eaking cycle extended form 24 hours to 25- 32 hours- his days became longer

  •   Body temperature circadian rhythm became more stable – extened to 25 hours slightly .
  • Sleep-wake cycle desynchronized from his body temp rhythm

Evaluation:Single case study can’t be generalized

  • Aschoff et al (1965) found that students kept in underground bunkers had extended sleeping patterns from 25-27 hours
  • Under normal circumstance the inbuilt rhythm is perfectly synchronized with the outside world it is only under conditions such as these can be observe them acting independently
  • Volunteer?
  • No one could predict the effects of long periods of free running bio rhythms /Reported feeling of depression/ suicidal thoughts and memory problems
  • Lasting psychological issue due prolonged isolation
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Disrupting Bio Rhythms :External zietgebers that gradually change such as light throughout the year provide enough time for our internal body clocks to adjust however human society has produced situations in which zeitgebers change rapidly having a dramatic effect on the bio rhythms e.g. jet lag or shift work

1. Shift work: working patterns which enable factories and organization’s to work around the clock. It means that employees are often required to work at times when they should be sleeping. Shift work therefore causes major disruption to bio rhythms.

  • Estimated that 1/5 Americans are in shift work (Coren 1996) such as junior doctors or nurses
  • Many shift workers are operating heavy and dangerous machinery at times when hey should be asleep and body clock is completely out of synchronization with external world
  •  Leads to effects on performance /frequent reports of fatigue /depression/illness
  • Body clock prepares us for sleep when it is dark especially around 2-4 am and it there have been many disasters such as Chernobyl which have occurred in this time frame
  •  Decisions made that led to the loss of the challenger were made be technicians who had been working 10-12 hour shifts for 2 weeks thus affecting judgment
  • Night shift workers then have to work during the day and this sleep can be disrupted by light/ activity in the house/ wanting to be awake for social interactions. So night shift workers may be sleep deprived as well as suffering desynchronization
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Czeisler,Moore-ede and Coleman ( 1982)

  • Utah chemical plant used traditional backwards shifts rotation with 7 days on each rotation.
  • Workers reported high levels of stress, sleeping difficulties and health problems all affecting productivity
  • The psychologist then introduced forward shift work for 21 days to allow the body clock to adapt
  • After 9 months workers reported feeling less stressed with fewer sleeping difficulties and health problems and increased productivity

 Gorden et al ( 1986) found similar result with Philadelphia police officers. Moving from backward shift to forward shifts of 18 days

  • Reported 30% reduction on sleeping on the job
  • 40% reduction in accidents on the job
  • better sleep and less stress
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 Other approaches to coping with shift work:

1. Permanent non-rotating shift work :Phillips(1991) found similar results to Czeisler when she introduced permanent shifts to a Kentucky police force . Officers choose 1 of 3 eight-hour shifts to stay on permanently

  • allows body clock to synchronize ( 16- 20 days)
  •  not very popular as many people would not like to permanently be on night shift

 2.Planned napping during shifts: shown to reduce tiredness and improve performance ( Sack et al 2007) it is not popular with employees and employers

3. Improved sleep during the day for night shift workers: however this can be disruptive to family and social life thus adding another dimension of pressure

4.rapid rotation: rotating shift work patterns every 2-3 days to prevent circadian rhythm from adjusting. Howveer it means other time rhythms are out of synchronization

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Jet lag: jet lag can occur in people traveling east to west or west to east. It s caused by rapidly changing zeitgebers especially light

·       Phase delay: east to west. Arrive ahead of time and in order to adjust body clock sleep must be delayed. Phase delay is easier to adjust to than phase advance

·       Phase advance: west to east – time at destination is later than indicated by our body clock. Means body clock has to advance to catch up with local time

·       Jet lag is an unpleasant feeling of extreme tiredness, Depression and slowed mental and physical reactions

Example:

You arrive in New york from London with body clock 5 hours ahead of local time Body clock says to sleep at 5 pm and wake at 3 am but this not coincide with natural social hours to fit in with local time. So we are trying to be alert and active when our body is not. Leading to confusion and tiredness. Other body rhythms such as temperature may also be not synchronize adding more confusion and disorientation

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  • Coren (1996) travelling west to east  is worse than east to west
  • Jet lag can affect the alertness of cabin crew
  •  Recht,Lew,Schwratz (1995):looked at US baseball teams Over  3 year period of teams traveling – found that teams travelling east to west before a game won 44 % of their games but travelling west to eats only won 37% of their games .HE some teams may just have been better than other but it was carried over a long period of time meaning this should have evened itself out
  •   West to east is worse as it has higher demands on our body clock- body clock ends up behind local times and has to advance to catch up- appears body clock finds it easier to phase delay than advanc

Factors affecting severity of jet lag

  • Direcrion of travel
  • Number of times zone crossed
  • Age- Sack et al (2007) found that jet lag decrease with age
  • Individual differences: some are more resistant to jet lag – phase tolerant
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Techniques used to reduce jet lag (Coren 1996)

  • Sleep well before the flight- do not be sleep deprived
  • Adjust fight behavior in anticipation for the time at arrival destination. If its going to be light when you arrive stay awake and the opposite for dark
  • Avoid caffeine or alcohol
  • When you arrive immediately adjust to local zeigebers
  • Get out into the daylight as soon as possible –resynchronizes body clock
  • Melatonin could be used – Beaumont et al (2004) found that melatonin capsule given at bedtime 3 days before travel and for 5 days after significantly reduced jet lag
  • If trip is short there is school of thought that says you should stick to your normal sleep-wake cycle

Sack et al (2007) found that disruption of biorhythms and sleep deprivation led to weakening of the immune system

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Nature of sleep

·       Sleep is very important and essential to the human body

·       Dolphins have evolved a method in order to allow them to sleep underwater. One side of the brain sleeps whilst the other is awake allowing each side to get some sleep.

·       Others have perfected the method of micro sleep such as sharks ho sleep for a hew seconds constantly rater than long periods of sleep – theses adaptions show how essential sleep is

 

Types of sleep:

·       1950’s breakthrough in the study of sleep through the use electroencephalograph (EEG) uses electrodes on the scalp to record electrical activity of the brain

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Berger(1929) identified two major EEG patterns:

  • Desynchronized EEG: a reading that has no regular pattern of electrical activity. Recorded when the brain is in an active or aroused state –awake
  • Synchronized EEG: frequency is measured( Hz)-indicates that millions of neurons are firing together in unison – usually during sleep. Regular pattern of electrical activity- repeated waves which have a particular amplitude and frequency

Non-REM sleep (NREM)ONE OF 2 DISTICNTIVE TYPES OF SLEEP FOUND IN MAMMALS. As we fall asleep the pattern of waves becomes larger and slower therefore stages of 3-4 can be referred to as slow wave sleep

·       As we move from drowsiness through he stages of NREM to deep stage 4- HR/respiration/BP fall and blood flow to the brain decreases indicating decreased level of activity

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Stages of NREM

Characteristics

Stage 1:Theta waves (4-7 Hz)

Stage 2 :Dominated by theta waves but also with bursts of sleep spindles –phases of fast (12-16Hz)  lasting for a sec or so

Stage 3:Delta waves (1-4 Hz) and the no. of spindle waves falls

Stage 4:Dominated by large ,slow delta waves-deepest stage of sleep where people are most soundly asleep

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Rapid Eye Movement- REM

Aserinsky and Kleitman(1953) and Dement and Kleitman( 1957)found that after falling through he stages of NREM ppt move back up to stage 2 of lighter sleeping ( 75 minutes in sleep)

  • EEG then becomes very fast and desynchronized similar to an awake /aroused person but the body loses muscle and is in partial paralysis
  • Also movements of the eye
  •  HR and Bp increase aswell as penile erections and increased blood flow to the ******
  • It is still very difficult to wake the individual
  • Contrast between aroused brain and a sleeping state and largely unresponsive body led to it being called paradoxical sleep
  • REM last for 15 minutes and then moves bach into stage 2 and down the stages to stage 4,then the process repeats lasting 90 minutes for a complete cycle
  • 7-8 hours of sleep a night leads to 5 cycles of NREM/REM
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Dreaming: Aserinsky and Kleitman(1953) and Dement and Kleitman( 1957) found that Rem was associated with dreaming

  • Those waking up during REM reported dreaming  80% of the time compared to only 20% in NREM
  • Dreams reported during Rem more vivid than NREM
  • REM is a physiological state identified by objective methods but dreams are subjective so we cannot call it dreaming sleep

 Sleep and Bio Rhythms: Michel Jovet (1969) established the critical structures for the control of the REM and NREM lay in the ascending reticular formation ( RF- network of millions of neurons deep in the brain. Controls brains arousal state and within it are the centers for controlling the sleeping and waking)

  • Through a series of experiment by carefully lesioning the brain he was abel to locate the locus coeruleus that is important for REM sleep and the raphe nuclei being critical for NRE
  • REM seems dependent on noradrenaline and NREM dependent on serotonin 
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Functions of sleep

Evolutionary explanations of sleep:

  • Behaviors evolve and develop if they provide selective advantage for the animals involved
  • Sleep have evolved because it provides some selective advantages
  • This approach focuses on ecological niches

Factors:

  • Environment- terrestrial or aquatic e.g the dolphins adaptive sleeping abilities/ nocturnal or diurnal sleep patterns
  • Predator or prey: prey are normally herbivores and are clearly more vulnerable than predators especially when asleep
  •  Sleep site- safe burrow or exposed location
  • Size- larger animals sleep less than smaller animals
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Ecological factors

  • Predator-prey status: Meddis (1975) sleep keeps vulnerable prey animals safe at times when normal activities are impossible e.g. diurnal animals cant forage and therefore sleep to keep safe
  • Hibernation theory: Webb (1982) animals such as bears hibernate over winter in order to conserve energy at a time when hunting and foraging is impossible-waste of energy. Sleep is relative inactivity and allows energy conservation

 Research Evidence

  • Allison and Cicchetti (1976) studied sleep in 39 animals- prey animals sleep significantly less time than predators- might be due to the idea that they are more vulnerable during sleep and contradicts Meddis idea
  • Sleep leaves an animal unreactive and vulnerable if safety was the only concern then the animal would always be alert and awake
  • BMR is positively correlated with sleep time- higher the BMR the more the animal sleeps- small animals have a higher BMR than larger ones therefore they sleep more
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Lesku et al ( 2006) :Analyzed sleep data on more than 54 animals and looked at a range of variable- body mass/brain mass/BMR/Sleep exposure index (assessment of the animas sleep state and how safe it is )/trophic position( whether the animal is herbivore or carnivore)

Findings:

  • Brain mass is positively correlated with amount of REM sleep but not associated with NREM
  • Sleep exposure index is negatively correlated with amount of REM- the more dangerous the sleep site the less REM
  • Trophic level correlated with amount of Rem and sleep time
  • BMR is negatively correlated NREM and total sleep –the authors acknowledge that this previous findings is due to the difference is BMR calculations – Brain metabolic rate may be considered an important
  •   Brain mass is positively correlated with the amount REM sleep

Evaluation: Only correlation not cause and effect/High ecological validity as is based in observations of animals in their natural habitat

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Evaluation:

·       Research cannot confirm cause and effect therefore there may be an unidentified factor causing correlation

·       Evolutionary expiations always try to look fir the advantageous reason for it being present HE it may simply be neutral

·       Not reductionist- takes into account he animals lifestyle and the animal as a whole and its environment

 

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Restoration Theory:

  • Oswald (1966) suggested that sleep restores depleted resources of energy, removes waste from muscles and repairs cells. 
  • For example during the day waste chemicals build up in the muscles following physical exertion and neurotransmitters used for communication throughout the nervous system are likely to be used up. 
  • Sleep therefore might be an ideal time for the body to remove this waste and restock/replenish its levels of neurotransmitters in preparation for activity the next day.  As some have put it…life disrupts homeostasis; sleep restores it.  
  •  In addition the body could carry out repairs to damaged cells and growth could occur the young.

 

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Non REM sleep 

·       According to Oswald, NREM sleep is a time for replenishing the body. 

·       Oswald points out that most NREM sleep, especially stages 3 and 4, occur at the start of the night when the body is most tired. 

·        During stages 3 and 4 we secrete greater levels of growth hormone into the blood which would help in the repair process, seeming to offer support to his theory.  

·       We do know that many restorative functions appear to occur during sleep, for example digestion, removal of waste from muscles etc. and protein synthesis for repair and growth.  However, these processes also occur whilst we are awake too!

 

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Evidence in support of restoration theory

  •  Shapiro (1981) who studied ultra marathon runners who had completed a 57-mile run.  It was found that they slept for 90 minutes longer than usual for the next two nights.  REM sleep decreased whilst stage 4 of quiet or NREM sleep increased dramatically from 25% of nights sleep to 45%.
  • Horne and Minrad found that tiring activates led ppts going to sleep quicker but did not sleep any longer
  • However, lack of exercise does not reduce amount of deep sleep as this model would predict.   Repack and Lewis (1971) got healthy students to spend 6 weeks in bed and observed no change in their sleep patterns. (Note: Carrying our sleep research on student sleep patterns seems to be as valid as research on the sleep patterns of cats).  
  • When we lose sleep and are given the opportunity to make it up we only catch up on a small proportion of it.  This suggests that not all sleep is needed.  Why therefore would we need non-essential sleep?  
  • Amino acids are not stored in the body and only remain in the bloodstream for about eight hours before being broken down or excreted.  As a result we would expect protein synthesis to stop half way through a night’s sleep.  This would explain why deep sleep occurs in the first half of a night’s sleep.  Of course this also assumes that we eat just prior to going to sleep!
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REM sleep

  • Oswald (1980) and Hartman (1984) built on the theory to include restoration during REM sleep.  They believe that REM is for restoration of the brain. 
  • Stern & Morgane (1974) believed that neurotransmitter levels within the brain may be restored during REM sleep.  The young brain is growing and developing at its fastest rate so young children, especially babies sleep for much longer than adults.  In the newborn about 9 hours a day is spent in REM compared to about 2 hours in adults.  
  • Note: restoration theories of sleep make cognitive sense since we suffer so many unpleasant consequences when deprived of sleep

Effects of sleep deprivation:

  • Peter Tripp (American DJ) stayed awake foe 201 hours –later he developed signs of mental disturbance and paranoid delusions – at the end he slept for 24 hours and felt normal when he awoke
  •   1964- Randy Gardener (American student) stayed awake for 264 hours – developed blurred visions/speech became disorganized/mildly paranoid- 1st night he sleeps 15 hours/ following night he recovered about a ¼ of sleep – 2/3 of sleep was deep NREM and 50% of sleep was REM
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Conclusions about Total sleep deprivation (TSD)

  • People can endure long terms of TSD without any long term effects
  • TSD can have effects on metal functioning –show significant individual differences
  •   After TSD only a small portion of sleep is recovered
  • Recovery is concentrated on deep stages of NREM and REM

Evaluation:

  • Case studies must be treated with caution
  • Tripp and Gardener may have had periods of ‘micro sleep’
  • Prolonged sleep deprivation leads to death in non-humans –in rats this occurs within 19 days but stressful situations must be used in order to keep them awake such as having them fall in a water bath- so we are not able to distinguish between the effects of sleep deprivation or stressful situations
  • Human Fatal Familial insomnia where individuals sleep normally until middle age and then stop sleeping- death usually occurs within 2 years –associated with thalamus – difficult to determine between the effects of underlying brain damage or sleep deprivation
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Sleep labs: Polysomnography, also called a sleep study, is a test used to diagnose sleep disorders. Polysomnography records your brain waves, the oxygen level in your blood, heart rate and breathing, as well as eye and leg movements during the study.

Horne’s restoration theory (1998)

  • States that both REM and stage 3 & 4 of NREM (SWS) are for brain restoration.
  • He also suggests that REM and SWS NREM make up 'core sleep', and that light NREM is 'optional sleep', with the main function being to keep the animal inconspicuous or to conserve energy.

Evidence for:

  • Lab studies show sleep deprivation affects cognitive processes in the brain (i.e. attention, perception, memory).
  • Sleep deprivation doesn't appear to have an effect on the body.
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Horne’s and Pettitt (1985) :Investigated whether incentive would overcome the effects of sleep deprivation

  • Groups 1 + 2 were deprived for 72 hours
  • Group 1 were not given financial incentive
  • Group 2 were given financial incentive
  • Group 3 were not sleep deprived as control
  • Ppts tested on auditory and had to respond when they heard a tone was slightly shorter

Findings:Group 2 was as good as the control group after 1 night of sleep deprivation

  • Group 1 performed significantly worse even after 2 nights without the sleep group 2 still performed significantly better
  • Ppts recovered and performed normally after 8 hours of sleep-not all sleep was necessary for the return of normal cognitive functions

Conclusion: Motivation provided by the financial reward could overcome the effects of sleep deprivation –sleep deprivation effects (initially motivation more than cog abilities but sleep deprivation does affect.

Evaluation:Groups were very small (5 ppts) –hard to generalize/Sleep deprived ppts would have ‘micro sleeps’- there was no checking if this was comparable across all ppts/There should have been a control group who were sleep deprived but also with incentive/ Ethics: sleep deprivation is stressful

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Horne proposed:

·       REM /deep NREM are essential for normal brain function

·       REM/NREM is known as core sleep

·       Light NREM seems to be of no obvious use known as optional sleep-suggest it may have a role in keeping the animal inconspicuous

·       When entering NREM there is a surge of a growth hormone in order to repair damaged tissues howver this require amino acids but this may no longer be available as it is 6 hours or more after the evening meal- therefore it seems the use of hormone is unclear but it is unlikely to include tissue repair

·       Suggest that repair to the body may be done in periods of ‘ relaxed wakefulness’

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REM Rebound: this is seen after people are specifically deprived of REM in sleep labs. When allowed to sleep they show a dramatic recovery of REM and this is REM rebound. This is evidence supporting the importance of REM sleep.

  • People on anti-presents often show reduction in REM sleep and no REM when they come off drugs
  • Stern and Morgane (1974) suggest the function REM is linked to the synthesis of neurotransmitters used up in daytime activities. Anti-depressants increase the level of these neurotransmitters and therefore less REM is needed
  • Brain restoration view also explains the high proportion of REM sleep in new born babies- the brain is growing rapidly with new synaptic connections every day if REM is important for the growth and development of neurotransmitters and synaptic connections then it would make sense for babies needing long periods of REM sleep
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Evaluation:

  • Studies on non-human animals can be invalidated due to the stressful environments needed to keep the animal awake

·       Sleep deprivation produces paranoia, confusion and hallucinations

·       Evidence strongest for restorations is for the brain process

·       There is little evidence for restoration for body tissue during sleep

·        Energy expenditure during REM sleep is similar to the mount of energy used when awake, HE growth of neurotransmitters requires energy

·       Restoration theories ignore the evolutionary theory and therefore in a sense they are reductionist

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Memory consolidation:

  •  Theory that sleep may be the time in which memories from the day are consolidated into permanent memories
  • The effects of the sleep may not actually the sleep stages but rather the quiet and being undisturbed
  • Problems with early studies is that they failed to account for being quiet and undisturbed
  • If you learn something at night you may recall it better in the morning because there is no interference and not because sleep itself is essential for consolidation
  • Karni et al (1994) used selective disruption of NREM and REM sleep and showed that improvement on simple visual discrimination tasks depend on REM but not NREM
  • Walker et al (2002) showed that motor learning improved if sleep followed training but not if training was followed by a similar a similar period of wakefulness. There was also an additional positive correlation between the amount of improvement and the amount of stage 2 NREM.
  •  The best form of evidence is involving simplest form procedural memory such as riding a bike.
  • The idea that dependence of more complex memory on sleep is inconsistent
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Lifespan changes in sleep chnages

  •  Function of sleep changes for the different ages causing the amount of sleep necessary to change
  • Babies will sleep for 16-20 hours a day with 50% being REM sleep
  • Premature babies born at 30 weeks will may experience up to 80% REM sleep indicating that things go on during sleep
  •  Sleep patens will settle down during the first year
  • How sleep patterns change

  • Endogenous biological rhythms are synchronized with signals from the outside world
  • Synchronization will happen in the first year
  • Around the age of 1 the rest-activity patterns are stabilized and 6-8 hours of sleep at night replaces the 1-2 hour naps
  • Proportion of REM approaches the adult ration of 25% and between one and two years the adult pattern of sleep-waking is established though may still have short naps in daytime
  • BUT are sleeping patterns changing during rest of our lifespan
  • Keep in mind individual differences with sleeping patterns and most is meta analysis and trends 
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Supporting research

  • Ohayon et al (2004)did a meta review on 65 studies of sleeping patterns and age range of 5-102
  • Found that the total sleep time decreased from about 470 min at 5 to 370 min at 70 showing that at we get older sleep times decrease
  • He also found that the increase of NREM as we get older lighter sleep for old
  • The most significant decrease was the percentage of deep NREM from 24% at age 5 to only 9% at 70
  • Floyd et al (2007)confirmed his findings of a decrease in REM of 0.6% per decade
  • Ohayonalso looked at gender differences finding males to have a higher mean score of total sleep time whereas females showed a higher percentage of stage 2 NREM in comparison
  • Over our lifespan there is a decrease in sleep efficiency due to the fact that older people have more episodes of waking during sleep
  • Older people have more sleep disorders 
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Commentary

  • Why are babies different from adults? Growth. Therefore greater amounts of REM sleep in needed as that is restorative etc and babies are constantly learning
  • REM is also linked to the production of neurotransmitters and consolidation of memories
  •   Sleep is an adaptive mechanism which is shaped to make ones parents lives easier
  • Changes during teens linked to hormone imbalance – released at night disturbing sleep
  • Physiological changes in old people result in reduced sleep for the old which can be experienced in terms of problems with staying asleep such as apnoea or illness
  • Reduction of deep sleep at old age reduces the production of growth hormones explaining some of the symptoms associated with old age – bone density, lack of energy

Issues debates and approaches 

  • Cultural differences – many studies have shown that social factors which are different in many different cultures have affected the sleeping patterns of people 
  • Sleep duration is shorter in Asia than Europe 
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Disorders of sleep

  • Dyssomnias– problems with the amount and timing of sleep (insomnia narcolepsy)
  • Parasomnias– behavioural or psychological events during sleep (sleepwalking or nightmares)
  • Insomnia:Problems with falling and staying asleep and reduction in the quality of sleep so that it is non-restorative
  • This leads to tiredness during the day affecting work and social functioning

Diagnostic criteria

  • Sleep onset latency of more 30 mins
  • Sleep efficiency of less than 85% and increase of night time awakenings
  •  More than 3 or 4 times a week
  • Transient insomnia lasts less than a week and generally the result of jet lag or exams etc
  • Short term insomnia lasts between 1-4 weeks
  •  Chronic or clinical insomnia lasts for over a month and has significant distressing effects on day time work due to tiredness and irritability
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Primary insomnia

  • Chronic with no obvious psychological or physical cause and not associated with other sleep problems
  • Most severe form is idiopathic insomnia which begins in childhood and will last a lifetime
  • Not linked with anxiety or arousal but in some cases it is linked to depression
  •  It’s thought that primary insomnia is caused by a basic malfunction in our sophisticated slep control systems which is genetic as there is evidence that idiopathic insomnia runs in families
  • Insomnia is associated with clinical anxiety states such as GAD(Generalized anxiety) or OCD but this is usually secondary insomnia

Secondary insomnia Many cases of chronic insomnia are associated with psychological or physical or Parasomnia so will be referred to as secondary

  • Common causes can be psychological disorders such as depression, anxiety states and school and have been found to be the cause of ±40% of those seeking treatment
  • Medical conditions such as heart failure, Parkinson’s and asthma can lead to insomnia
  • Drugs can lead to insomnia such as amphetamines or overuse of sleeping pull which lead to disrupted sleeping patterns
  • Parasomnias – sleep apnoea which when a person stops breathing while sleeping which leads to disrupted sleep
  • Fatal familial insomnia
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Explanations and treatments – risk factors

  • Age and gender: Older people are more likely to be sufferers due to old age illnesses such as arthritis or diabetes which will disrupt their sleeping patterns leading to insomnia
  • increased of insomnia in women can be related hormonal functions that come with age
  • sleep apnoeas: the pause may last from a few seconds to  minutes and can occur 5-30 times an hour which will result in major disruption
  • other Parasomnias include snoring, sleep walking and increase the likelihood that a person will experience insomnia
  • personality factors: individual differences in sleeping habits
  • the shortest sleeping time validated in sleep lab is about an hour per night
  • insomnias have been found that they were more likely to internalise all psychological disturbances rather than acting out problems or being aggressive
  • proposed that internalisation leads to higher levels of emotional arousal and increased likelihood of feeling anxious which is a risk factor
  • twin studies show that high levels of sleep disturbance were associated with high levels of neuroticism
  • neuroticism is significantly correlated with anxiety
  • Vahtera et al showed that sleep disorders following a traumatic life even such as divorce is highly correlated with personality trait of anxiety
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Drugs:

  • If insomnia is secondary to depression then the depression can be treated can lead to reduced insomnia
  • Nitrazepam (Mogadom) is a sleeping pill- the most prescribed drug for psychological disorders
  • Whilst increasing sleep sleeping pills reduce the quality disrupting normal ultradian pattern of REM and NREM sleep. Can lead to morning sleepiness and increased insomnia when drugs are stopped

Stimulus control therapy

  • Idea that insomnia is a conditioned response to the nighttime environment or the bedroom
  • Therefore in order to treat insomnia a new response must be associated with the nighttime environment

·       Morin et al (1999)

  •  Only going to bed when sleepy
  •  Only using the bedroom for bedroom related activities
  • Waking and getting up the same time every morning
  •  Not taking naps during the day
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Cognitive behavior therapy

  • They become very anxious at bedtime
  • The more they try to sleep the more they cant
  • They think they need to get to sleep quickly in order to 7-8 hours of sleep in order to cope with the day’s activities
  •  CBT is aimed at reducing/ correcting these faulty cognitions
  • Causes of insomnia are discussed and ideas such as needing 7-8 hours of sleep are challenged

Over arousal:

  •   Relaxation techniques are used to combat this
  • Progressive muscle relaxation
  •    Imaginary techniques used to reduce physiological arousal
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Gregory et al (2006)

  • Investigated the relationship between family conflict and later development of insomnia
  •  Longitudinal study
  • New Zealand- group of children were followed from their birth (1972) to present day
  • Family conflict was a variable studied – assessed using questionnaires to evaluate tension, hostility and distress in the family
  • Included events such as separation or divorce

Findings:Found the degree of distress faced by children between 15-18 were significantly correlated with the frequency of insomnia at 18

Conclusions:Their study demonstrates a possible casual connection between family conflict and later sleep problems .Suggest that insecurities lead to high levels of anxiety and a tendency to focus on family difficulties- links to research showing that insomnia is linked with anxiety

Evaluation:Actual incidences of insomnia was only 15% -majority being female- small group to study/Study only correlational/Researchers admit that correlation was a modest/Use of children-consent

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Personality factors and genetics:

  • Average – 7.5 hours of sleep- 16% sleeping more than 8.5 hours- 16% sleeping less than 6.5 hours
  • Sleeping less and more are associated with slight increases in morality – no known mechanisms for this
  • Sleep patterns seem to be relatively stable characteristic with a significant genetic component
  • There are no clear psychological or personality differences between long and short sleepers

Clinical anxiety:

  • Insomnia associated as a secondary cause of anxiety
  • Associated with high levels of arousal
  • Twin studies have shown that high levels of sleep disturbance were associated with high levels of neuroticism  (Heath et al 2998)

·       Vahtera et al (2007)

·       Vulnerability to sleep disorders following traumatic life events is highly correlated with an anxious personality trait

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Chronotype:a personality type defined by when in the circadian rhythm of sleep and waking when you are most alert

  • Early birds-larks or night owls or an intermediate type who functions well throughout the day
  • The difference between early and late people is a genetic difference and is based on the bio rhythm of sleep and waking cycle
  • Circadian rhythm in early rises is approx. 2 hours ahead of night owls (Kerchof and Van Dongen 1996)
  • Theses traits are distinctive ad stable throughout life and are a personality trait
  • Controlled by our endogenous pacemakers which is controlled by the ‘clock’ genes on our chromosomes
  •  7 clock genes identified
  •  More women than men suffer from insomnia as women have higher levels of neuroticism and anxiety
  •  Changes in the menstrual cycle (hormone changes) can influence sleep aptterns
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Chronotype:a personality type defined by when in the circadian rhythm of sleep and waking when you are most alert

  • Early birds-larks or night owls or an intermediate type who functions well throughout the day
  • The difference between early and late people is a genetic difference and is based on the bio rhythm of sleep and waking cycle
  • Circadian rhythm in early rises is approx. 2 hours ahead of night owls (Kerchof and Van Dongen 1996)
  • Theses traits are distinctive ad stable throughout life and are a personality trait
  • Controlled by our endogenous pacemakers which is controlled by the ‘clock’ genes on our chromosomes 
  • 7 clock genes identified
  • More women than men suffer from insomnia as women have higher levels of neuroticism and anxiety
  • Changes in the menstrual cycle (hormone changes) can influence sleep aptterns

 

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Other sleep disorders

Sleep Apnoea

·       Repeated episodes of breathing failure during sleep lasting for 20-40 seconds

·       Clinical diagnosis = at least 5 episodes a night

·       Feature include snoring/morning headaches/dry mouth in the morning

1.     Obstructive sleep apnoea: obstruction of the upper airways, preventing efficient passage of air to the lungs this could be due to enlargement of the tissue at the back of the mouth or the tonsils swelling. Highly correlated with obesity.

2.     Central sleep apnoea: caused by problems in the brains control of breathing and respiration. Associated with a choking sensation. Often linked with heart problems or cerebrovascular disease

Treatment:

·       Surgery can widen the upper airways for OSA

·       Weightless can also be effective for OSA

·       Breathing mask creates continuous airway pressure

·       Drugs can be used to treat underlying cause of CSA such as cardiac problems

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NarcolepsyThis will affect around 1 person in 2000 and there are characterized by 4 major symptoms

Symptoms:Extreme day time sleepiness, with short repeated episodes of sleep throughout the day

·       Cataplexy is the sudden unexpected loss of muscle tone while awake especially during transitional period between sleeping and waking up. Can be brought on by emotion arousal such as laughing or sexual arousal

·       Sleep paralysis is an inability to move which often happens when falling asleep or waking up

  •  Hypo genic hallucinations: REM dreams occurring during the switch from sleeping to waking
  • 50% of suffers show all symptoms
  •  During sleep the body loses muscle tone-accounts for cataplexy and sleep paralysis if it occurred during waking behavior
  • Symptoms of narcolepsy reflects the invasion of REM
  • In the 60s the view was that it was linked to malfunction in the system regulating REM explain some of the classic systems of narcolepsy accompanies REM sleep and intrusion of REM type sleep into daytime sleep
  • People with narcolepsy move straight into REM sleep- immediately show cataplexy
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Commentary

  •  REM hypothesis proposed after Vogel observed REM sleep at onset of sleep in a narcoleptic patient
  • This explanation was supported by recordings of neuron activity in brainstem of narcoleptic dogs showed that cataplexy is linked to the activation of cells that in normal animals are active during only REM sleep
  •  But general research hasn’t been convincing

HLA

  • Research in the 80s indicates that narcolepsy was linked to a mutation of immune system
  • Honda found increased frequency of one type of HLA (human leukocyte antigen) in narcoleptic patients
  • HLA molecules found on the surface of white blood cells and coordinate the immune response

Commentar

  • Narcolepsy-HLA link continues to be researched through specific HLA variant found commonly in narcoleptics and is not found in all narcoleptics
  • And also reasonable common in general population meaning that HPA cant be the sole explanation
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Hypocretin/Orexin

  • Lack of orexin or its receptors was the cause of narcolepsy in humans
  •  Confirmed by Thannickal et al (2000) who found that Orexin producing cells in hypothalamus of the brain is involved in sleep and were drastically reduced in people with narcolepsy
  •  Recently research uncovered link between neurotransmitter hypocretin (a.k.a. orexin) and narcolepsy
  •  Orexin also seems to plays an important role in maintaining wakefulness
  •  Evidence comes from narcoleptic dogs who have a gene mutation on chromosome 12 (Lin et al 1999)
  • This gene is responsible for regulating brain receptors for Orexin
  •  Such as the locus of control and raphe nuclei, increases levels of REM which suggests that Orexin is centrally involved in the control of REM sleep ATM we can’t explain the loss of hypothalamic Orexin producing neurons Narcolepsy usually develops during adolescence and while mono zygotic twins have a higher concordance rate than dizygotic but only around 30%
  • Injecting orexin into areas of the brain involved in sleep increase elevls of REM (Wickens 2005)
  • This suggests that the condition is not completely inherited environmental factors are also important. Reduction in Orexin also due to brain injury, infection diet or stress or possibly it’s also the result of an auto-immune attack
  • Stimulant drugs such as methylphenidate (Ritalin), amphetamine or modfinal act against daytime sleepiness.
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Sleep walking:

  • Occurs in 30% of 12-15 year olds as a parasomnia (event during sleep)
  • Tends to run in families
  • Takes place in the deeper stages of NREM early in the night and not during REM due to loss of muscle tone
  • During sleep walking the individual usually carries out a routine
  • Often have no recollection of what they have done even awoken during the even
  • It is harmless but if it causes distress to the individual or the family it is classified as a disorder
  • Suggestions that it is the desire to sleep where they slept as a child but this does not explain all the range of automatic movements
  • Freud’s theory can be used- it is used as a time to work through unconscious anxieties
  • Moving from NREM to REM prevents this process so unconscious instinctual energies spill into NREM and are channelled into motor activities
  • Natural explanations brain image studies indicate that the brain is in a different state during sleepwalking
  • Bessetti suggests that sleepwalking is the result of selective activation in some areas of the brain and the inhibition of other brain areas
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Sleep walking:

  • Increased cerebral blood flow was observed in the cingulated cortex which is thouh to be the brain area that regulates emotional behaviours
  • Decreased blood flow was found in the prefrontal cortices which is consistent with the lack of awareness and insight observed in sleepwalkers
  • Oliviero suggested that sleepwalking is based on what we already know about physiological mechanisms controlling sleep
  •   Usually the release of GABA during sleep prevents activity in the brains motor system causing loss of muscle tone
  • Sleepwalking is more frequent in children because this system is underdeveloped and insufficient qualities of GABA allow motor activity
  • Oliviero speculates that adult sleepwalking is due to inhibitory GABA mechanism remaining undeveloped in certain individuals
  • Sleepwalking is a primary sleep disorder in its own right and can occur as a result of other factors such as drug use etc
  • Sleepwalking is caused by a variety of prescription medication like valium and beta blockers and drugs which are intended to help improve sleep

·        

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Nightmares and night terrors

·       Nightmares occur during REM sleep and have a story like structure which can be recalled in detail

·       Night terrors relate to when the individual wakes up in a terrified state, screaming and crying. They can be difficult to wake and when awake they remember little of the experience except maybe a single image

·       Occur in both children and adults

 

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