Theories of Sleep:The restoration function AO1

How would you explain…

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?

Objectives

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.

Why do we sleep?

Sleep stages

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

SWS and Growth Hormone

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 proteinsare fragile and need to be renewed constantly – This is part of the body’s natural recovery process

SWS and Growth Hormone

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.

SWS and Growth Hormone

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

SWS and the immune system

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

REM and Brain Growth

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.

REM and Brain Growth

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.

REM and NeurotransmittersSiegel and Rogawksi (1988) suggest REM allows for a break in neurotransmitter release.

This in turn allows neurons to regain sensitivity andallows the body to function properly.

REM and antidepressants

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

REM sleep and memory

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.

REM sleep and memory

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 and REM sleep

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.

To evaluate

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

Theories of Sleep:The restoration function AO2

By the end of the lesson

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.

Evo Resto

Study 1

Study 2

Methodology

IDA

Real-World Application

Evolutionary / RestorationStudy Support Refute

Study Support Refute

Evo vs Resto??

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?