Restoration explanations for sleep

Psychology unit 3 aqa a A2

  • Created by: lauren
  • Created on: 09-06-12 18:49

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Sleep for restoration? When we have a lack of sleep we experience feelings of tiredness and function less effecitively. We sleep to prevent these feelings and to restore physiological systems that have been active during the day.Sleep has a homeostatic function - sleep restores physiological systems to their optimal level

Oswald - observed patients who were recovering from brain damage - spent more time in REM sleep - deep stages of NREM surge of growth hormone - growth hormone essential for maintenance and repair of body's physiological systems - proposed REM sleep for restoration of brain systems - NREM for physiological system restoration

Horne - theory based on large number of lab based sleep deprivation studies - assume assesing the effects of not sleeping will help us understand function of sleeping - reviewed over 50 studies - mild sleep dep - little or no effect - what effects there were effected cognitive functions such as perception, memory and attention - when pp's were allowed to sleep they recovered much more of REM and deep NREM than the lighter stages of card

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Horne used this evidence to propose that REM and deep NREM 'core sleep' were essential for maintaining brain systems that underlie cognitive processes - light NREM - no function - he called it optional sleep - bodily restoration not associated with sleep and it happens during relaxed wakefulness

Animal deprivation studies - severe sleep deprivation in rats leads to death - Everson&Rechstaffen - supporting restoration - although keeping rats awake means constant arousal and stress - if they fall asleep they fall into water - causes stress - may not be clear if it is the sleep deprivation causing death or the stress - no single cause of death has been found so it supports the stress idea - use of animals - different physiology and different ability of cognitive thoughts - problems generalizing non-human animals to animals (diff sleep patterns also) Human deprivation studies - Peter Tripp - awake for 201 hours - became unpleasant, abusive, hallucinate and paranoid, decline in body temp - his waking brain waves were practically indisguishable to those of a sleeping person - Randy Gardner - awake for 260 hours - no significant psychotic symptoms - both reported feelings of normality after a lengthy sleep - Hai Ngoc - stopped sleeping in 197 - no ill effects

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Case studies - Peter Tripp and Randy Gardner do provide valuable research and can be useful in describing individual differences in the effects of sleep deprivation however case studies are fairly uncontrolled compared to lab studies and the unique features of the individual may not typify the behaviour of others - low population validity - also it is likely that people who do volunteer to take part in sleep deprivation studies all posses a certain characteristic, this could be that they have no issues with sleeping and are highly motivated to try and cope well with sleep deprivation - presents more issues with generalisability

Energy expenditure - If Oswald is correct - expending energy should lead to extended sleep the following night as the body needs to restore its physiological systems - findings not consistent - Breedlove - evidence that exercise causes people to fall asleep faster but not for longer - doesn't support Oswald

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Growth hormone - Oswald noted surge of growth hormone during NREM linking to restoration of body tissues in REM - Horne points out for growth hormone to promote protien synthesis there needs to be a supply of amino acids - amino acids part of our diet and only available for a few hours after a meal - by the time we sleep amino acid levels are low so its unlikely much tissues restoration could take place regardless of growth hormone surge

Fatal familial insomnia (FFI) - rare inherited condition - sleep normally until middle aged then stop sleeping - death usually occurs within 2 years after they stop sleeping - although this seems parallel to the death in rats from sleep deprivation - FFI is linked to the damage of the thalamus in the brain - likely death may be caused by the damaged thalamus than the sleep deprivation

Restoration and evolutionary - not necessarily alternatives - sleep may be important for the restoration but the actual timing and patterning of sleeping may depend on the range of evolutionary and ecological factors in the past

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Reductionist? we sleep because its our instinct to want to restore our psychological and physiological functioning - evolutionary - however if we learnt to sleep at a young age, rather than having an inbuilt instict to sleep - through direct reinforcement we learnt that sleep makes us feel psychologically and physiologically better therefore we repeat this behaviour to gain the positive feeling. So it can be argued that one simple explanation can not explain such a complex phenomenom as sleep, although it does try to help us to understand it by putting it in a simple context

Methodological issues - involves lab based sleep deprivation studies in humans - these have high levels of control but low levels of ecological validity so may not represent sleep deprivation that may happen in real life which could be caused by psychological disorders

Ethical issues - lab studies on animals - methods used are unethical and highly stressful such as thr Everson and Rechstaffen study which caused high levels of stress to the rats that may have in fact caused them to die - researchers have to question themselves to whether the research is necessary - use only the amount of animals they need 

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