Outline And Evaluate Restoration Explanations For The Functions Of Sleep 8 16

Outline and evaluate restoration explanations for the functions of sleep [8 + 16]

intro: Aleep is divided into several different stages. SWS and REM sleep are associated with particular benefits. Oswald (1980) proposed that each of these had different functions - slow wave sleep enables body repair and REM enables brain recovery.
SWS – initiates body repair (Oswald)
Growth hormone – important in childhood because it stimulates physical growth. Important throughout lifespan for protein synthesis and cell growth as cells constantly need to be replaced. secreted to some extent durning the day but mainly in SWS. Demonstrated by the reversing of the sleep wake cycle in the study by Sassin Et al where the growth hormone is then produced during the day when SWS takes place. This is further supported from the findings of van Cauter and Plat who found that the amount of growth hormone correlates to the amount of SWS The immune system – body’s defence against viruses and bacteria. Lack of SWS is associuated with reduced immune functioning (Krueger et al)
A02 – If sws and rem sleep is restorative, total sleep deprivation should have negative effects
+ case study – Peter Tripp stayed awake for 201 hours and after 5 days experienced hallucinations and paranoia; his brain rhythms looked like he was asleep  Non-human animal studies also show that lack of sleep may be fatal. Rechtschaffen et al kept rats on a rotating disc and after 33 days they died, although this may have been due to stress than lack of sleep.
However..
 sleep deprived individuals may be getting some sleep e.g lab observations found that sleep deprivation for more than 72 hours results in micro sleeps while pps are ‘awake’ but experiencing some benefits of sleep.
 Another case study by Randy Gardner found no psychotic symptoms after 11 days without sleep and there are no reports of individuals (e.g. Nick Ngoc) who haven’t slept In years without Ill effects. This however may be explained through the idea that the individual is experiencing micro sleeps. methodological issues..
- case studies relate to unique individuals and other sleep studies often use volunteers who also might have unique characteristics (needing less sleep than the norm) so results might lack generalisabilty
- non human animal studies might lack generalizability because animals have different sleep requirements tohumans.
If SWS is important, SWS deprivation should have negative effects.. demonstrated in ‘rebound effects’ – when people are deprived of SWS they show need for more sws on subsequent nights acoustic stimulatuion is used to wake sleepers as soon as brain wave show SWS (Ferrara et al)
REM – initiates brain repair (Oswald)
Brain growth – infants have greater proportion of REM sleep than adults, which suggests that REM sleep may be important to brain growth.
Siegel suggests that the amount of REM sleep in any animal is proportional to the immaturity of offspring at birth e.g platypus young are v. immature and have 8 hours, dolphin young are v. mature and have almost no REM sleep
Memory – REM sleep may permit memories to be sorted and discared if unwanted (crick and Mitchison) rem may be important in the consolidation of procedural memory (memory from doing things) where as SWS is important for semantic (meaning) and episodic (events) memory (Stickgold)
A02 – If REM sleep is important, REM sleep deprivation should have negative effects...
+ research evidence that shows REM deprivation results in as much as 50% more REM sleep on subsequent nights (Empson)
If sws and rem are restorative, exercise should increase the need for sleep.. exercise should use up proteins, etc necessitating more sleep restoration. Shapiro et al found that marathon runners slept 2 hours longer after a race..
However..
Horne and Minard found that a series of exhausting tasks led people to go to sleep faster but not for loner.
IDA – the evolutionary approach – main alternative to restoration theory is the evolutionary approach, which claims that sleep has no specific benefit except protection (to conserve energy to keep an animal safe from predators) rather than performing some specific biological function as calimed by the restoration approach. the restoration approach doesn’t explain, for example why some species sleep one hemisphere at a time (dolphins) nor does it explain why lack of consciousness is necessary. it looks like environmental pressures are important in shaping sleep processes, which can be explained by the evolutionary approach.