Biological Rhythms

Updated 2009-06-04 12:39

Research into circadian, infradian and ultradian rhythms

Siffre (1975)When spent 6 months in a cave, circadian rhythm extended to 25 hours.
Aschoff + Weaver (1976)Placed ppts in an underground bunker and found that most circadian rhythm lengthened to 24-25 hours, although some were as long as 29 hours.
Folkard (1985)When tried to reduce ppts circadian rhythm down to 22 hours, most people couldn’t get any lower than 23 hours.
Czeisler (1991)Could alter ppts circadian rhythms down to 22 and up to 28 hours with dim lightning.
Czeisler (1999)Huge individual differences occur - circadian rhythm can vary from 13-65 hours.
Folkard (1977)Temperature cycle - STM better in morning, LTM better in afternoon in 12-13 year olds.
Monk + Embrey (1981)Alertness is best when body temperature is lowest, in early morning and early evening.
Hawkins + Armstrong-Esther (1978)Circadian rhythms: Nurses doing shift work took longer to adjust their temperature rhythms than their sleep=wake cycle.
Russel (1980)Infradian rhythms: When sweat from one group of women rubbed onto lips of another group, 4 out of 5 menstrual cycles synchronised to within a day of the donor.
Reinberg (1967)Infradian rhythms: When a woman spent 3 months in a cave, her menstrual cycle decreased to 25.7 days.
Freidman + Fisher (1967)Ultradian rhythms: Observed a 90 minute cycle in terms of eating+drinking behaviour of psychiatric patients.

Research into Endogenous Pacemakers and Exogenous Zeitgebers

Darlington (1998)Endogenous pacemakers: Proteins CLOCK+CYCLE loop opposite with PER+TIM in our biological clock.
Decoursey (2000)Endogenous pacemakers: Destroyed SCN in chipmunks and found that circadian rhythms were disrupted.
Morgan (1995)Endogenous pacemakers: Bred mutant hamsters to have a 20 hour circadian rhythm, then transferred SCN into other hamsters, who also adopted the 20 hour rhythm.
Hall (2000)Exogenous zeitgebers: Other locations of the body besides the eyes contain proteins to detect changes in light.
Campbell + Murphy (1998)Exogenous zeitgebers: Shining light on back of ppts knees shifted circadian rhythms.
Miles (1977)Exogenous zeitgebers: Studied a blind man whose circadian rhythm was 24.9 hours.
Czeisler (1995)Exogenous zeitgebers: Found that some blind people do respond to very bright lights by inhibiting melatonin secretion.
Luce and Segal (1966)Against exogenous zeitgebers: People living within the Arctic Circle, where the sun never sets, still sleep for 7 hours.
Kelly (1991)Against exogenous zeitgebers: US submariners could not adjust to an 18 hour day despite social cues + lighting.

Research into disrupting biological rhythms

Knutsson (1986)Increased risk of heart disease after 18 years shift work.
Czeisler (1986)Bright light can be used to mimic effect of daylight to combat effects of shift work.
Recht (1995)Effect of jet lag: found that baseballers won more games when travelling East to West (phase delay)