When people are asleep there are not in a total loss of consciousness but a gradual reduction in awareness. Sleep occurs in stages and they are started of by the alpha stage this is where there is smooth electrical activity and this is seen as a state of relaxation as there is slow heart rate and reduction in muscle tension. The second stage the beta stage is where there is irregular electrical activity and this is associated with a state of arousal the Person can also be woken easily. Theta activity is associated with an EEG (electroencephalograph) and this occurs during early stages of slow wave sleep and REM sleep.
The last stage of sleep is delta activity this is where there is regular electrical activity and occurs during the deepest stages of slow wave sleep and people in this stage of sleep are hard to wake and hormones are also secreted round about now. The EEG is an objective measure of sleep it shows the electrical activity of the brain. There are different patterns of activity at different times during sleep without these researchers would have to rely on subjective measures such as asking people to self report. The Restoration theory focuses on restoring tissue and saving energy.
In order to repair muscles proteins need to be synthesised. So during REM sleep there is more energy expenditure and also a good blood supply so therefore less protein synthesis taking place. The NREM occurs during slow wave so enables the body to repair there is a significant increase in secretion of growth hormones during slow wave sleep. REM sleep is (rapid eye movement) it occurs in brief spurts of increased activity in the brain and body. REM is considered the dreaming stage of sleep and is characterised by the rolling of the eyes under the eyelids.
NonREM is a state of sleep that is characterised by four stages that range from light dozing to deep sleep. 75% of sleep is spent in NREM. One main researcher Oswald (1970) suggested that both REM and NREM sleep is needed to restore us both physiologically and psychologically. He suggested that NREM sleep is needed more to restore bodily processes so a relinquish of energy as it has been used up during the day and that REM sleep is when neurochemicals that have been used up in the day are regenerated by protein synthesis.
We can break down restoration into two parts psychological restoration is mainly dealing with insomniacs these are sleep problems that are characterised by difficulty in falling asleep this is more clear to see by looking at the symptoms of jet lag. The symptoms are thought to be caused by the releases of the hormone melatonin which is out of step with the environment the person now finds themselves in. This results in drowsiness during the day and insomnia during the night.
The second part of restoration is physiological restoration this is shown by the sleep pattern of babies and foetuses they spend an average of 18hours a day sleeping and use about half of the 18hours in REM sleep. This is opposed to 8 hour sleep that adults have and they spend about a quarter of that in REM sleep. This shows the larger amount of brain activity that occurs in developing brains and a lot of protein synthesis is needed for cell and synaptic growth.
From this both physical and brain protein synthesis are dependant on growth hormones which are secreted after the first bit of delta activity in slow wave sleep. The second theory is the evolutionary theory this has two parts to it the conservation part and the protection part. Meddis (1979) suggested that in order for animals to protect themselves they would sleep and this would increase there chances of safety as the animals would be immobile and therefore would be less likely to be noticed by predators.
An example of this would be the sleeping pattern of dolphins. The dolphins in the River Indus only sleep for a few seconds at a time repeatedly through 24 hours. Marine dolphins only sleep with one hemisphere at a time showing that they do this to protect themselves from predators, the theorist Webb (1982) supported the view that sleep helps to conserve energy but also thought it allowed animals to become more aware of an able to avoid predators.
Apart from looking at marine animals it’s clear to see animals that graze such as sheep need little sleep as they are vulnerable and need to eat in order to gain energy and also it makes them more vigilant as they are moving about a lot more and can attract the attention of predators. Animals that hunt are at little risk from predators for example lions these need lots of sleep as this is away to keep them safe and conserve a lot of energy.