Flashcards in Sleep & Dreams (Czeisler et al 1990 case study) Deck (13)
Describe Czeisler et al ( 1990) case study
"Exposure to bright light & darkness to treat physiologic maladaptation to night work " Changed the level of light to which night workers were exposed - bright light during 8 hrs work & darkness for 8 hrs during sleep hours alllowed the body's circadian rhythm to adjust to night shift in 2/3 days
Problems of Czeisler et al (1990)
Shiftwork disrupts biological rhythms & following accidents occurred between 1-4am - Bhopal (chemical accident) , 3 mile island(nuclear accident) & Chernobyl ( nuclear accident)
What were the instructions in the case study ( Czeisler)?
-asked to stay in complete darkness from 9am to 5pm. -controls were given no specific instructions. -all completed cognitive tasks hourly otherwise would do own work. -control group worked during night in ordinary indoor light(150lux). -experiment group worked under bright illuminations of 7000-12000lux equivalent to every morning light
What did Czeisler 1990 make sure participants do?
-8 men (22-29) , none had worked regularly on night shifts before. -no sleeping dissorders. -none had been jet lagged in the past 6weeks
What was the method of Czeisler ?
2 week Experiment , 5 control condition & 5 treatment condition
What did Czeisler believe about shift work ?
That shift work environments that are warm and dimily light are counter productive & belived that exposure to bright light at night & darkness during day could help shift workers resynchronise better
Describe what happened in the 2 week of Czeisler study
1st week base line study & 2nd week night shift work -men lived at home buy reported for work at lab each night in the 2nd week , 2 men one control , one treatment did not conform to protocol so their results were excluded
What was the problem that Czeisler found out about shift work ( another study)?
7.3 million Americans work at night but research has shown that a complete adaption of endogenous circadian rythmms does not occur even after years of shift work
What were the results ?
(Treatment study slept 2hrs longer than control) 1) significant shift in body temp nadir between 1&2 between control & treatment condition (the endogenous pacemaker was adapting ). 2) behavioural changes- same behaviour but shown an hour later in treatment conditions. 3) alterness & performance -the treatment conditions were more alert than control by end of week 2
What were procedure meassurmensts ?
Measure body temp ( typically when circadian body temp is at lowest 4:30am). -blood samples from were collected every 15-25mins on random. -alertness was asssed 3 times an hour using an calculator & subjective awareness. -urinary excretion rates. -plasma cortisol concentrations
What was the evaluation- strengths ?
This is a well controlled experiment that contained many different physiological measures to isolate cause and effect , overall they showed endogenous pacemaker is hard to shift but they are things we can do to adapt
1) biological reductionism - this portrays the body as a machine like which automatically adjusts to natural zeitgebers such as light & social explanations such as more noise in daytime,stress could occur from loss Contanct family 2) Czeisler et al claim that questions still to be answered concern - variability between individuals (age/sex) & duration / intensity of light needed for optimal adaption to night work