free running studies
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- what were the aim of free running studies?
- To identify the nature of the circadian rhythm. Whether, when normal zeitgerbers were removed, if rhythms were endogenous and therefore continue with the same period length. If rythms would stay snchronised as in the normal environment, or if something else would happen.
- What were the findings initially?
- that almost all the measures continued the same as they did in the normal timed environment.
- What happened to the period length of some individuals?
- they found that many people had a free running circadian rhythm of a bit more than 24hrs, more like 24.5-25hrs. ie when given the choice they chose to go to bed an hour later each night and sleep later the next morning.(phase delayed)
- what happened to the body temp cycle and the sleepwake cycle in some individuals?
- they became desynchonised or uncoupled. In some,The CBT stayed at around 24hrs and the sleep/wake increased to 34hrs and in others the sleepwake became shorter while the CBT stayed around 24hrs.
- What general conclusions were reached from the free running studies/
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-once uncoupled, the CBT and the S/W cycle took on their own consistent period lengths.
-the coupled period length was always a compromise between the two.
-the coupled period length was always closer to the CBT - what is the SCn?
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the suprachiasmatic nucleus.
Light activates the SCN through the eyes. the SCN keeps our sleepwake cycle entrained to the environment. it is the body clock. - which is the stronger rhythm?
- the core body temp rhythm
- What is the X oscillator?
- Core body temperature. This controlled urine production, plasma cortisol, REm sleep
- What is the Y oscillator/
- onset of sleep. this controlled skin temp and growth hormone.
- REM propensity has its own circadian rhythm.What is the peak REm sleep propensity time?
- 8-9am. it occurs at certain phases of the CBT rythm as it follows the X Oscillator.
- How many hours after Tmax is sleep likely to occur/
- 4-5
- How many hours before Tmin is sleep likely to occur?
- 5-6
- What was the average period length of the sleepwake cycle in young indid=viduals in the free running studies?
- 24.5 - 25hrs
- When the sleepwake cycle and the CBT cycle desynchronise, which one stays closest to the coupled period length and why?
- the CBT because it seems to be the stronger of the two.
- How much influence do the x and Y oscillators have on each other?
- the X oscillator exerts four times as much influence over the y oscillator.
- If the SCN is allowed to determine behaviour on its own without any external zeitgerbers, what is likely to happen?
- The period length will be anywhere between 23.5 -25 hours. This sometimes happens in blind people with optic nerve damage.
- After desynchronisation, do the CBT and the sleep wake cycle take on consistent period lengths?
- Yes, consistent.
- Is growth hormone secretion determined by the core body temp or the sleep onset cycle?
- the sleep onset cycle
- Which is urine formation linked to?
- the x oscillator - CBT. so that when the CBT and the sleep/wake get out of sync, sometimes max urine is produced during sleep!
- Is REm sleep propensity linked to X or Y?
- X - CBT.
- Is skin temp linked to X or Y?
- To Y - sleep/wake or activity.
- When looking at sleep onsets across the whole CBT 24 hour rhythm, when did most sleep onsets occur?
- at Tmin and a secondary sleepy period in the early afternoon 4-5 hours before Tmax.
- When looking at sleep maintenace zones, when were the least number of sleep onsets?
-
at Tmax and a few hours after
in the morning when CBT is on the increase (9-11am) - What is the difference between the aim of the free running studies and the forced desynchrony studies?
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free running studies - aimed to look at when one chose to sleep and wake
Forced desynch studies - looked at how possible was it to sleep and wake at different times across CBT cycle. - In forced desynchrony studies how did they measure how hard is was for one to sleep at a certain time?
- by measuring sleep onset latency.