Outline one theory of the function of sleep

physical restoration because during this sleep the pituitary gland releases a growth hormone which is important for tissue growth, protein and RNA synthesis and the formation of blood cells. Adam and Oswald supported this, because they found that tissue restoration such as cell repair occurred during this sleep. Also Shapiro et al (1981) found that people taking part in a 57 mile ultra marathon slept longer than normal people the next two nights and spend longer in the Stage 4 of sleep in order to give time for their body to recover. However this study is not very reliable because it has also been found that inactivity does not reduce the need for sleep, because Ryback et al (1971) found no change in the sleep required by people who spent six weeks in bed. This suggests that sleep is not only for restoration because otherwise people would have to sleep even less when they haven't done any exercise. There is also little evidence to suggest a lot of exercise makes you sleep longer the only difference is to appears to be that people fall asleep faster. Horne and Milard found that when participants were given exhausting tasks to do and the only difference was that they fell asleep faster; therefore this implies that sleep does not have a restorative function. It has also been found that stage 4 sleep declines with age possibly due to the lack of growth hormone needed. The effects of a lack of stage 4 sleep has been investigated by Rechtschaffen et al (1983) who did a study in which he deprived rats of sleep by using an apparatus that forced them to walk when they showed signs of sleepiness. However if they didn't walk they would fall into the water that surrounded them. There was another group of control rats that were exposed to the same apparatus but were allowed to sleep normally. It was found that after 33 days all of the sleep-deprived rats had died, whereas the control rats demonstrated no ill effects. The sleep deprived rats also showed physiological problems such as dramatic weight loss and other problems, i.e. stomach ulcers. These physiological symptoms may have occurred due to the stress brought about from the lack of sleep gained, but this is not certain and could be due to other factors. Also it is difficult to generalise the findings to humans, as they may not produce the same results when deprived of sleep. Jouvet (1967) used cats and the 'flowerpot technique' to show the importance of REM sleep. A cat was put on top of a flowerpot, which was surrounded by water. Whenever the cat slipped into REM sleep the loss of muscle tone caused the flowerpot to tip over so the cat fell into the water and woke up. The cats deprived of REM sleep died eventually, which indicates a lack of REM sleep can cause ill effects. These findings cannot be generalised to humans because they may not produce the same psychological problems as the cats in the experiment. However similar experiments cannot be conducted on humans because it would be considered more unethical than using the cats; therefore humans have only taken part in studies of partial sleep deprivation, which is when people are only allowed to sleep for about 4 hours every night and there is less effect on performance as the lack of sleep is reduced over time. Selective Deprivation studies by Dement (1960) involved waking participants over a number of nights every time they entered REM sleep. A control group was also woken but only in NREM sleep. It was found that the REM deprived people had to be woken about 12 times and this rose to 26 times by the last night. There was also a rebound effect of a 60% increase in REM sleep at the end of the study. The participants displayed physiological problems such as impaired concentration, increased eating and an increase of stress and anxiety levels, which supports the physical restoration theory as when deprived of sleep the participants did suffer ill effects. It has also been said that REM sleep involves the restoring of neurotransmitters, but REM sleep involves a lot of neural activity, which makes it difficult to see how they could be restored. Overall this theory is not reliable because it is not known what the restorative processes are. Psychological restoration is when you sleep to restore your psychological functions; as if you do not gain this sleep it can cause ill effects. Research by Naitoh (1975) explored the effects of one night's sleep deprivation on a person's mood and found that the effects were negative because people were described as been less friendly, less relaxed and less cheerful than people who hadn't been deprived of sleep. Berry and Webb (1983) also reported a strong positive correlation between levels of anxiety and sleep efficiency. However this is a correlation study, which means that cause and effect cannot be inferred and so there may be other reasons why this particular pattern has occurred. Kales et al found that insomniacs suffer more form more psychological problems than non-insomniacs. This study is retrospective, because it is looking back on a study and is not comparing the effects to how they were before. Huber-Weidman (1976) showed that sleep deprived people had more psychological problems than physical problems. A study of Peter Tripp supports these ideas. He carried out a 'wakeathon' for charity, which meant that he stayed awake for eight days and it was found that he developed psychological problems, such as hallucinations and delusions, which led to paranoia, rather than physiological problems. A similar study by Gulevich et al (1966) assessed Randy Gardner who managed to stay awake for 11 days. It was found that as time went on that he developed psychological problems, which meant that his mood became more negative and his task performance deteriorated. He also displayed some physiological effects, such as slowing of the EEG and a decline in body temperature. These studies show that lack of sleep can cause ill effects on psychological functions and therefore are reliable in explaining that sleep is vital for restoring the mind to avoid these. However these studies can be criticised for lacking reliability, because they were only case studies and so there will have been a certain lack of control. There also may have been demand characteristics in the Randy Gardner study, which meant that Randy Gardner may have known that the experimenter was expecting a particular outcome; therefore this may have influenced his behaviour. In conclusion it can be seen that physical and psychological restoration are important theories of sleep, because they state that if we are deprived of sleep we are more likely to suffer from mind and body ill effects. These ideas have being mainly supported by sleep deprivation studies on animals and humans. However these studies are not completely reliable as they have been criticised for lacking reliability. Therefore more studies will have to be done in order to provide reliable evidence to suggest that restoration is a good explanation of why we need to sleep. Sleep Questions Rebecca Johnson Miss Hall