Sleep is devided into slow wave sleep (SWS) and REM. Oswald proposed SWSaided in body repair and REM aided brain recovery. During SWS, growth hormone is released aigining in development during childhood and during adulthood it enables protei synthesis and cell growth aiding in bodily recovery. It has also been suggested that lack of SWS can result in redcued functionis of the immune system.
REM sleep is highest in babies and higher in premature babies. This may be due to humans being born immatues and requiring rapid brain growth and development. Animals born mature have little REM sleep suggesting a link between REM and neural development, another restorative function.
Siegel et al proposed REM sleep allowed for a break in neurotransmitter activity therefore allowing the neurons to regain sensitivity. Neurons are vital for bodily functioning. Anti-depressantcs have been seen to increase levels of neurtransmitter and abolist REM as a side effect, assumed to be due to receptors not needig to be regenerated. This highlights a possible link between neurtransmitter restoration and REM sleep.
Dement et al woke cats each time they entered REM sleep and found all the cats died highlighting lack of sleep can have serious consequences. However, other confouding variables such as stress of the environment may have contributed to the cats death therefore the study lacks internal validity as it was not purely a measure of sleep deprivation. Ethical issues are a concern as this could be have seen as a form of animal torture and it is questionable whether it can be justified as in the name of science. Results from cats cannot be generalised to humans therefore the study may not be justifiable and lacks external validity. However, it is clear that sever sleep deprivation has negative effects, even if indirectly linked to stress.
Horne proposed a distinction between core and optional sleep. Core sleep is equivalent to SWS and optional is equivalent to REM. Optional sleep is argued to be dispensible and used to occupy unproductive hours and used to conserve energy. However, restoration theorists would argue REM plays an important role in brain functionins and is not simply used to waste time. Evidence of the importance of sleep is seen in human case studies of deprivation.
Peter Tripp, stayed awake for 201 hours and suffered severe negative effects such as abusive, unpleasant behaviour and suffered hallucination and paranoia. Contrasting this, Randy Garner beat Tripp's record but suffered non eof the negative effects Tripp had shown. Restoration theories are reductionist as individual differences are not considered. From researchwe see individuals cope with deprivation differently and therefore will likely have different levels of restorative function from sleep. However, single case studies have low external validity making it difficult to draw firm conclusions regarding the restorative function of sleep. However, both experienced REM rebound helping conclude sleep likely provides a restorative function.
Restoration theories are limited as they cannot explain all sleep patterns. For example the EEG recordings of dolphins have found no evidence of REM sleep. Yet resoration theory suggests REM sleep is needed for brain restoration. Sleep differences cannot be explained and to suggest sleep only holds resorative function may be resductionist and over simplified. Some may argue an evolutionary approach would lead to better understanding of sleep as different environmental pressures would have shaped sleep patterns. However, during sleep animals become essentially paralysed leaving them vulnerable, suggesting sleep must have an important restorative function as they repeated put themsleves at risk during sleep.
Research findings from Dement and the two cases studies highlight that sleep deprivation has sever consequences. These uch consequences can vary between individuals, but most research can help us draw the conclusion that sleep aids in some restorative function, although we cannot determine the extent of restoration that sleep has. Positive application of research could aid towards better sleep hygiene helping to reduce the negetaive effects of sleep deprivation and/or help to prevent it.
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