Why do we sleep?

• Think about times in a persons life when they might sleep LOTS……

• What might this tell us about why we need to sleep?

Restoration Theory of Sleep

I can outline the restoration theory of sleep

I can describe some studies and case studies that support or undermine the restoration theory

I can evaluate theories using AIDS

E

C

A

O + E One or more functions of Sleep (24)

Restoration Theory of Sleep

Oswald (1980)

SWS enables your body to repair itself

REM sleep enables your brain to repair itself

Make some predictions – If this is true then……………….

Predictions of Oswald’s theory

1. Sleep deprivation will lead to a deficit in functioning

2. You get a ‘rebound’ following deprivation

3. There is an increase in REM during brain growth, reorganisation & repair

4. There is an increase in SWS during illness, recovery from injury

If sleep (SWS& REM) is restorative, total sleep deprivation should have negative effects…..

Animal StudiesRechtchaffen kept rats on a turning disc they died after 33 days The effects of total sleep deprivationCase studies e.g. Peter Tripp stayed awake for 201 hours and

after 5 days experienced hallucinations and paranoia.However…..Microsleep (Williams et al)BUT Randy Gardner found no Psychotic symptoms after 11 days

without sleep.

Sleep deprivation will lead to a deficit in functioning

• 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).

Sleep deprivation will lead to a deficit in functioning

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

AIDs• Methodological issues………• Case studies • Issues with animal studies• Ethical issues

The effects of sleep deprivation

The effects of Partial sleep deprivationRebound effects (Empson 2002)When people are deprived of SWS they showthe need for more SWS the next nightThe same for REM sleep.

You get a “rebound” following deprivation

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

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 h

our

peri

od

Age

5yrs

Brain GrowthMore REM sleep in babies and even more in premature babiesSuggests REM sleep may be important for brain growth.Siegel suggests the amount of REM in any animal is related to how immature they are at birth.

Evidence that REM sleep enables brain recovery.

Growth hormone is secreted during SWSImportant in childhood & for protein synthesis & cell growth.THIS IS VITAL IN THE RESTORATION OF BODY TISSUE

What happens in old age?

Evidence that SWS enables body repair

The immune system

Lack of SWS has also been associated with reduced functioning of the immune system.The immune system consists of various proteins and anti bodies which are regenerated during cell growth and protein synthesis in SWS.

Evidence that SWS enables body repair

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

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-

Jouvert 1967Cats placed on islands of flower pots floating in water. They could balance on the pot and enter stages 1-4 sleep but in REM muscles would relax and cat would fall into the water and wake up. So REM deprived. The cats became disturbed and died after about 35 days

Randy Gardener/ Peter Tripp

Newborn babies spend up to 18 hours asleep

Horne 1988Amino acids which form proteins come from our food. Therefore if amino acids are to make protein during SWS we would need to go to bed within five hours of eating as this is how long they remain in the body! We don’t usually manage this though!

Shapiro et al 1981Runners sleep patterns were studied and found that those runners in a marathon slept for an extra hour on 2 nights following a race. It was their SWS which increased. Compared to non race days sleep.

Neurotransmitters restored REM requires a lot of neural activity of the brain. How could this restore neurotransmitters? Surly it would in fact use them up!

Restoration Theory of Sleep

I can outline the restoration theory of sleep

I can describe some studies and case studies that support or undermine the restoration theory

I can evaluate theories using AIDS

E

C

A

O + E One or more functions of Sleep (24)