Functions of sleep; restoration.

Restoration theory;Different stages- Oswald Oswald proposed that REM sleep was a time for restoration of brain systems, while NREM was a time for restoration of the body's physiological systems.Ao1- Slow-wave-sleep;Growth hormone's secreted during SWS. GH stimulates growth and is important during childhood. Also important in adulthood because it enables protein synthesis and cell growth to take place this is vital in restoration of body tissue because proteins are fragile and constantly renewed. GH secreted during the day but most is released at night during SWS. Oswald found that patients who were recovering from brain damage spent more time in REM sleep, in deep NREM there was surge of GH. Sassin et al- when sleeping cycles are reversed by 12 hours (person sleeps in the morning and gets up at night) the GH release is also reversed- it's controlled by neural mechanisms related to SWS. Couter and Plat found that GH release correlated with amount of SWS and decline of GH in older age is associated with reduce SWS. The immune system; Lack of SWS's been associated with reduced immune system functioning (Krueger). The Immune system consists of protein molecules which regenerate during cell growth and protein synthesis in SWS.REM Sleep: Brain growth; Active/REM sleep is higher in babies which is explained in terms of brain growth. It's suggested that the amount of REM sleep is proportionate to the immaturity of offspring at birth. E.g. dolphin can swim from birth so had nearly no REM sleep. This suggests a relationship between neural development and REM sleep.Neurotransmitter activity may be affected by REM sleep. Siegel and Rogawski suggested REM allows for a break in neurotransmitter release which permits neurons to regain their sensitivity and allow the body to function properly. Support for this comes from MAIO's-drugs aimed to increase levels of neurotransmitter in monoamie group such as dopamine and serotonin. A side effec is abolishment of REM activity. It's suggested that the increase of monoamies means monoamine receptors don't need to be revitalised and therefore no need for REM sleep. REM sleep and memory; Crick and Mitchson proposed that REM sleep, unwanted memories are discarded thus making more important memories accessible. Recent research found a more complex relationship- Stickgold found REM may be important in consolidation of procedural memory (skills such as riding a bike) whereas SWS sleep is more important for semantic memory (knowledge and meanings) and episodal memory (events).Horne- laboratory sleep-deprivation studies to assess the effects of not sleeping-50 stydues and concluded: effects were cognitive, perception and memory, when they were allowed to sleep they recovered more REM and deep NREM. So, Horne proposed that REM and deep NREM (together called core sleep) were essential for maintaining brain systems. Light NREM has no function.

Ao2-Oswald noted that a surge of growth hormone during NREm sleep was linked to the restoration of body tissues during REM. However, Horne found that for GH to promote protein-synthesis (and restore tissues) there must be a supply of amino acids. Amino acids are a part of our diet but are only available for protein synthesis for a few hours after eating. By the time we sleep, levels of amino acids are low and unlikely that much tissue restoration could take place even with surge of the growth hormone.A second consequence of sleep as restoration is that an increased physical exercise should lead to an increased sleep in order to restore the proteins and biochemicals used which appears to be the cause in some studies. Shapiro found runners in a marathon slept about 1 hour more on the two nights after a race. SWS increased which supports the view than NREM sleep is associated with physical recovery. However, in general research found intense exercise doesn't do anything more than make someone fall asleep fasrer, Horne and Minard gave pps exhausting tasks to see if it would increase their sleep duration and found that although it made pps go to sleep faster, they did not sleep for longer. Therefore, although there is evidence of sleep for restoration purposes, there is also research rejecting it. There have been comparative studies. Even though sleep is universal, sleep varies between animals. EEG studies of dolphins found they don't have any REM sleep, but if REM sleep is vital for restoration why don't dolphins need it too? Similarly, fur seals have no REM when at sea but do when they're in land. This leads to the question of why is it necessary to become unconscious/sleep for vital biological processes to take place? Young suggested that the more we know about other species sleep patterns, it become more apparent that the environmental pressures provide the key to understanding sleep, not restoration pressures. Therefore, findings from comparative studies lead to rejection the restorative function of sleep.The effects of sleep deprivation are inconsistent. Some studies suggests that lack of sleep doesn't result in long-term damage e.g. Randy Gardner, who stayed awake for 264 hours and 12 minutes. Although he had difficulties doing some tasks he didn't have severe disturbances and when catching up on sleep, he seemed to recover completely. Also, Vietnamese Hai Ngoc is reported to have stopped sleeping in 1973 without any ill effects. Williams found that when participants have been monitored they were found to have short periods of micro-sleep while awake therefore 'non-sleepers' are getting the benefits of sleep while still awake. This therefore showed that sleep deprivation didn't have negative effects long-term on individuals. On the other hand, various non-human studies suggested that sleep deprivation. Rechtschaffen et al forced rates to remain awake and physically active by rotating a disc they were standing on every-time they fell asleep. After 33 days all rats died. Although, it is possible that it was the stress rather than the sleep deprivation which caused the death. In 2005 Rattenborg et al conducted a similar experiment with pigeons and no pigeons suffered ill effects. But, we do have to take into account that these studies were laboratory studies with high levels of control and low levels of ecological validity, also methods used are highly unethical and highly stressful making results unreliable therefore having major methodological issues. Overall, conclusions on the effects of sleep deprivation could not be made.