Two main theories: 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

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

Evidence for restoration theories Total Sleep Deprivation Studies Partial Sleep Deprivation Studies (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 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 psychlotron.org.uk

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 EEG recordings show that microsleep is the same as sleep

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 24 hour period Age 5yrs psychlotron.org.uk

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 etc X 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 Homewor k – q 4 p13 For Against