The restoration function AO1

Why, when we do not have enough sleep, we don’t feel very good? When we have had a good night’s sleep, we feel refreshed?

 Today you will  Learn about the restoration explanation of sleep  So that you can  Write 8 marks’ worth of AO1 to describe the restoration explanation of sleep

The evolutionary explanations are that sleep is an adaptive advantage to preserve energy or keep animals safe from predators Another likely explanation is that sleep allows vital biological functions to take place, which improve our bodily systems, and allow us to maintain good health.

Two of the stages we learned about in previous lessons are associated with particular benefits for our biological systems.  Oswald (1980) proposes:  SWS enables body repair  REM sleep enables brain recovery

Growth hormone is secreted during SWS This is important especially in childhood but adults also need (GH) because it enables protein synthesis and cell growth This is essential as proteins are fragile and need to be renewed constantly – This is part of the body’s natural recovery process

GH is secreted in pulses all day, but a large amount is secreted at night, primarily during SWS Sassin et al (1969) found that when sleep-wake cycles are reversed the release of GH is also reversed. This shows GH is controlled by neural mechanisms related to SWS.

Van Cauter and Plat (1996) found that the amount of GH released correlates with the amount of SWS. Van Cauter et al (2000) also found that decline of GH in old age has also been associated with reduced SWS

Krueger et al (1985) found that lack of SWS has also been linked to reduced functioning of the immune system. The immune system contains various protein molecules (antibodies) which are regenrated during cell growth and protein synthesis in SWS

The percentage of REM/active sleep in babies is far higher than adults. This may be because they are growing rapidly - premature babies have even more REM It has been suggested that the amount of REM in any animal is proportional to the immaturity of the offspring at birth.

The platypus is immature at birth and has about 8 hours REM a day, whereas dolphins, can swim at birth and have almost no REM sleep (Seigel, 2003) This suggests a relationship between neural development and REM sleep.

Siegel and Rogawksi (1988) suggest REM allows for a break in neurotransmitter release. This in turn allows neurons to regain sensitivity and allows the body to function properly.

Antidepressant drugs such as MAOIs aim to increase the levels of monoamines such as dopamine and serotonin. They also have the strange side effect of abolishing REM activity completely. This suggests a link between REM and neurotransmitters. The increase in monoamines mean the monamine receptors don’t have to be revitalised, therefore, there is no need for REM sleep

There has been a supposed link between memory and REM sleep for a long time. Crick and Mitchison (1983) proposed that REM allows us to discard unwanted memories, making wanted ones more accessible.

Stickgold (2005) suggests a more complex relationship between memory and sleep. REM may be important in the consolidation of procedural memory (related to skills like riding a bike, or tying shoelaces etc) SWS sleep may be more important for semantic memory (related to knowledge and meanings) and episodic memory (memory for events)

Alcohol is known to suppress REM sleep. This may explain why people feel tired after a night of drinking, despite having has plenty of sleep. The lack of sufficient REM sleep leads to REM deficit and tiredness.

 You should now use your worksheets from evolutionary explanations, along with material in text books to collect as many evaluative points as you can.  You should also be able to create at least one methodological criticism as well

The restoration function AO2

 You need:  1 IDA  1 real-world application  1 methodological  2 studies (support or refute)  For each of the two theories.  You may want to do it as a table e.g. EvoResto Study 1 Study 2 Methodology IDA Real-World Application

StudySupportRefute StudySupportRefute

Discuss with your group which of the two explanations for sleep you think is best? What are your reasons for this? How do you think you might evaluate these explanations?