A01 Restoration theory
Restoration theory proposes that sleep is a time for restoration of physiological systems, especially the brain, that are active during the day. For example, Oswald (1980) found that damage to the brain through a drug overdose, increased the amount of REM sleep in an individual. This suggests that REM sleep is important for brain restoration.
A02 Shaprio exercise, sleep longer
Further supporting this idea, Shapiro et al found that after exercise, individuals would sleep for longer than usual, suggesting that they sleep longer in order to repair proteins or replace biological chemicals thus supporting the idea that restoration is taking place during sleep.
A02 Horne and Minardi, fall asleep faster not long
However, in Horne and Minardi’s study found that after physical exercise we fall asleep faster but we do not sleep for longer. This challenges restoration theory as Horne and Minardi’s study suggests that sleep duration is the same therefore there is no increase in the restoration process, even though the theory suggests that restoration takes place when there is loss of physiological components such as proteins – loss of these proteins would occur after exercise as the proteins would be used to help repair the muscles in the body. Therefore this suggests there is no link between sleep and restoration.
A02 REM earlier, sleep deprivated more REM
On the other hand, even though the participants did not sleep for longer, they did go to sleep faster so it could be argued that the participants entered REM sleep earlier than usual sleep and it could be REM sleep which is linked to restoration of the body as well as restoration of the brain. This is supported by Horne, he found that when participants are sleep deprivated they recover far more REM sleep than NREM sleep. Therefore it could be argued that the exhaustion from exercise in the participants may have made then slightly sleep deprivated and therefore the body restored during REM sleep, supporting restoration theory.
A02 Sleep dep, rats death
Further supporting this, Rachtschaffen et al found that several days of sleep deprivation in rats leads to death. This supports restoration theory as it suggests that the lack of sleep inhibited the restoration process that takes place during sleep, which resulted in death as physiological systems ceased to function.
A02 Stress, cortisol not clear relationship
An issue with this study however is that the rats were put under very stressful procedures in order to keep them awake. Therefore the relationship between sleep deprivation and restoration becomes unclear, as the stress could have been the cause for their death not the inhibition of restoration. Studies have shown that high levels of stress, inducing release of cortisol in human’s increases the likelihood of developing certain organ diseases, therefore the rats may have developed an illness that led to their death not sleep deprivation.
A02 Animal research, fatal familal insomia
It could be argued also that Rachtschaffen’s study lacks the ability to be able to expolate to humans as rats are genetically different to humans, therefore how can we be sure that we would behaviour in the same way? However supporting Rachtschaffen’s study, a rare human condition called fatal familial insomnia causes the suffer to become sleep deprived, and eventually death. This supports restoration theory as it suggests that sleep is important for us to be able to function and for survival, due to the clear link between death and severe lack of sleep in both cases.
The biological approach however can be challenged for its reductionist nature, the restoration theory assumes that with lack of sleep, the ability to restore ceases and therefore severe lack of sleep can lead to malfunction. But a man called Peter Tripp stayed awake for 201 hours, raising money for charity. He did develop severe hallucinations and delusions, but slept for 24 hours after his epic and awoke fully recovered. This suggests that some individuals will be affected more than others if sleep deprived, therefore restoration theory can be accused of reductionism as it ignores the aspect of individual differences. On the other hand, he did recover fully after his epic, so it could be argued that this case study does support the idea that sleep is for brain restoration.
A02/A01 Dolphins no REM
Dolphins are mammals just like humans yet they have no REM sleep which poses an issue to restoration theory. In addition even with no REM sleep they can still function effectively, suggesting that may be REM sleep in humans isn’t as nearly as important for us as other studies have proposed, other stages of sleep could be more important to our functioning such as slow wave sleep and NREM.
On the other hand, it could be argued that dolphins have evolved in a different environment to us, one of which they need to be continuously moving in order to survive. Therefore dolphins could have adaptively evolved to elimate the need for REM sleep in order to keep moving and survive. The survivors with this advantageous allele (without REM) would continue to breed and eventually the advantageous allele would be present in all dolphins. This idea can be supported by the fact that dolphins only sleep one part of their hemisphere at one time, suggesting that they cannot fully sleep in their environment.
A02 Difficult to generlise sleeps part
But the evolutionary approach, in this aspect may not be applicable to humans. As dolphins have evolved in a different environment to us, they may be mammals yet they are different species – therefore their sleep may differ to humans. This means it is hard to generalize dolphin research to humans, it may not be suitable to draw an explanation for human sleep from dolphins, meaning it lacks in reliability. However dolphins do still sleep a part of their hemisphere, which suggests that sleep is still an important feature in order to carry out our everyday lives, whether it has restoring properties or not.