Two main theories:

http://www.psychology4a.com/biological_rhythms.htm

1. Restoration theories

2. Ecological theories

Functions of Sleep – Restoration Theory

BATs

A01 Describe the restoration approach to the functions of sleep

A02/3 Analyse and evaluate research on the restoration approach to functions of sleep

A02/3 Consider evidence for memory consolidation during sleep

Synoptic points – case studies, sleep deprivation studies - validity

Why do we sleep?

Jot down 3 reasons why you think we need to sleep

The function of sleep is to allow the body to be

repaired/ restored

Did you know? ..Growth

Hormone is secreted during

SWS

Van Cauter et al 2000 – decline of Growth hormone in old age associated with reduced SWS

Hartmann (1973) said that REM sleep is a time for making neurotransmitters to compensate for the amount used during the day.Stern and Morgane (1974) also thought that that REM sleep allows the brain to restore levels of neurotransmitters to 'factory settings'.

Oswald (1980) claimed that NREM sleep restored the body and REM sleep restored the brain, through protein synthesis and that Slow Wave Sleep (SWS) helped the body restore itself.

Horne (1988) distinguished between core (SWS & REM) sleep and optional (stages 1 to 3) sleep

http://www.psychology4a.com/biological_rhythms.htm

Restoration theories

Horne (1988)

Oswald(1966)

A. SWS1-4 are all needed: for repair/restoration of the body

B. REM is essential: for repair/restoration of the brain

“Every stage of sleep is

essential for restoration!”

“No! Only SWS4 and REM are essential for

restoration!”

1. ‘Core sleep’ = SWS4 + REM:

essential for repair/restoration of the brain

2. ‘Optional sleep’ = SWS1-3: not needed at all for repair/restoration

Restoration of the body happens

when we are awake and relaxed

The main predictions of Restoration Theory are:

Deficits in functioning when sleep deprived

'Rebound' effects following sleep deprivation

Increase in REM sleep during brain growth, reorganisation and repair

Increase in SWS during times of illness or injury

http://www.psychology4a.com/biological_rhythms.htm

Evidence for restoration theories

Total Sleep DeprivationStudies

Partial Sleep DeprivationStudies (REM deprivation)

1. Everson (rats)

2. Michel Corke (case study – fatal familial insomnia)

3. Peter Tripp (case study – DJ – awake 8 days/nights)

1. Jouvet (cats)

2. Dement (human REM deprivation)

Dement (1960) Effects of REM deprivation were severe and included increased aggression and poor concentration.

Randy Gardner, a 17 year old student, stayed awake for 11 days (260) in 1965 and effects included disorganised speech, blurred vision, and a small degree of paranoia.

DJ Peter Tripp - 1959

Deficits when sleep deprived?

Stayed awake for 201 hrs in a ‘wakeathon’. After 3 days abusive, 5 days began to hallucinate (spiders in shoes).

Rebound effects?Dement (1960)PPs deprived of REM sleep

seemed to have a need to catch up Attempts to enter REM sleep doubled from an average of 12 to 26 times by the seventh night.

When allowed to sleep normally the participants spent much longer than normal in REM sleep, as did Randy Gardner.

Rebound

Generally, people catch up on sleep following deprivation

Not all lost sleep is reclaimed

About 70% of lost SWS and about 50% of lost REM typically recovered

Only some sleep is necessary

‘Rebound’ suggests that sleep is a necessary function

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Microsleep

When participants, being monitored, have been sleep deprived for over 72 hours they had short periods of MICROSLEEP while apparently awake.

Williams et al 1959 - EEG recordings show that microsleep is the same as sleep

http://www.psychology4a.com/biological_rhythms.htm

Which of these effects could be attributed to A) lack of restoration

of the brain?

A) lack of restoration of the body?

Increase in REM sleep during brain growth, reorganisation and repair?

Growth & reorganisation

• Reduction in sleep over lifespan

• Highest in infants; highest REM in early years

• Some changes in adolescence

REM

NREM

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Age

5yrs

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Total sleep time increases during illness

REM increases during recovery from brain injury, ECT & drug withdrawal

REM sleep and memory

Crick and Mitchison (1983) –

During REM sleep unwanted memories are disposed of – thus making more important memories easier to access.

Stickgold, (2005)

REM may be important to consolidate procedural memory (e.g.driving a car)

SWS important for consolidation of semantic memory (knowledge and meaning) and episodic memory (events)

Over to you …

• Read p12-13 and the ‘Restoration Theories of sleep’ worksheet.

• Do the ‘What you need to do’ activity

• Give one methodological criticism of each study.

Evaluation The FACE VALIDITY of this theory is high – it makes sense. It is easy to obtain quantitative (OBJECTIVE?) data on REM, amount of neurotransmitters etcX Extrapolating from hamsters, cats and rats to humans is always risky.X The research is not always RELIABLE and so we might question its VALIDITY. ( human sleep deprivation studies and animal sleep deprivation studies – fatal or not fatal?)X Case Studies- 'Alien Among Us' criticism

The main problem......is the lack of death among humans who are sleep deprived!!

Rechtschaffen et al 1983 – rats

died after being kept wake on a moving disc for

33 days.Stress more

likely the cause!

Plenary

Do question 3 p13 – try this method …

Draw round your hands

On one hand write the arguments that support Restoration Theory

On the other hand write the arguments against the Restoration theory

Homework – q 4

p13

For Against