Biological rhythms

Research into Circadian Rhythms

Siffre (1962)
Aschoff & Weaver (1976)
Folkard ( 1985)

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Aschoff & Weaver (1976)

Ppts spent 4 weeks in WW2 bunker
-All but one displayed circadian rhythm of 24-25 hours

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Folkard (1985)

Studied a group who lived in cave for 3 weeks.
Went to bed at 11:45pm and woke up at 7:45am
During the study clocks were put forward so what they thought was a 24 hour day only lasted 22 hours
-Only one ppt able to adjust

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Strengths of circadian rhythms

Practical application to drug treatment
-development of chronotherapeutics
Practical application to shift work
- Balvin (1996) & Knutsson (2003)

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Balvin (1996)

Night workers have reduced concentration around 6am, this is when accidents are most common

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Knuttson (2003)

Shift workers more likely to develop heart disease, likely due to stress of adjusting sleep/week pattern

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Research into infradian rhythms

Stern & Mcclintock (1998)
-Pheromones taken from 9 women at different stages of menstrual cycle
-Pheromones rubbed on top lip of 20 other women.
-68% of woman experienced changes in their menstrual cycle which synced them closer to their 'odour donours'

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Strengths of infradian rhythms

Evolutionary basis of menstrual cycle

Practical application to SAD
-Phototherapy effective for 60%

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Weakness of infradian rhythms

Methodological limitation of synchronization studies
-many confounding variables
- Small sample size

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Weakness of circadian rhythms

Individual differences
-Siffre (1962) & A&W (1976) lacks population validity.

-Zeisler (1999) suggests sleep/wake cycles vary from 13-65 hours

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Animal studies into endogenous pacemakers

Decoursey (20000
- Destroyed SCN in 30 chipmunks

Ralph (1990)

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Ralph (1990)

Transfered SCN cells from foetal tissue of hamsters with 20hr sleep/wake cycle to normal hamsters. Normal hamsters also had 20hr sleep/wake cycle.

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Evaluation of endogenous pacemakers

Beyond the SCN
-Many circadian rhythms (peripheral oscillators) that act independently
-Damiola (2000)

Ethical issues of Animal studies

Interactionist system

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Evaluation of exogenous pacemakers

Overstated influence
-Miles (1997) -Blind ppt unable to adjust sleep cycle despite being exposed to social cues

Practical application to age related insomnia

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Biological rhythms

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