circadian rhythms Flashcards
why are endogenous rhythms hard to study
because they are entrained - light, food social cues
we have to seriously mess up people’s routines to see what their natural circadian rhythms
constant routine protocols
method used to study circadian rhythms - getting rid of zeitgebers
- constant dim light
- kept awake for a long time
- meals at weird times, weird quantities
- no social cues (alone)
circadian rhythms
24 hour cycles (not just sleep)
what do we measure to find out endogenous rhythms
melatonin and body temp
how do we represent circadian rhythms
with waves - the distance between waves is the period - most people have a people of slightly longer than 24hours
what three processes orchestrate sleep?
Sleep is orchestrated by interactions between homeostatic, ultradian, and circadian processes
Ex of ultradian - not enough sleep last night=more sleep tonight, or took a nap this afternoon=a little insomniac tonight
what do we need to measure circadian period?
To measure circadian period we need more than 24 hours in constant conditions (constant routine protocols)
· Kept awake for a long time
· Dim light always
· Meals at weird times, weird quantities
Measured by:
- Sleep diary
- Actigraphy
- Body temperature
- Melatonin - in plasma
- Adults: circadian period is 24.15 h
what are the two competing needs of the circadian rhythm
Two competing needs: endogenous robust rhythm and able to adapt to environment
what is free running
‘free running’ rhythms in constant conditions - means rhythms that are not synchronized by zietgeibers
sleep in blind people
· Non 24 hour cycles
· Desynchronization from outside world
Weak effect of zeitgeiber entrainment - food/mealtime sometimes works but sometimes doesn’t
examples of sleep structures in blind people
○ Cortical blindness - could still have non image forming pathway - sleep usually not too bad
○ Delayed - very long sleep onset - can’t maintain sleep in the beginning
○ Shifted - a lot of slow wave sleep early in the night, can’t sustain rem in the morning (early riser)
Unclassified - sometimes can’t find a pattern at all
why don’t blind people have a true constant environment
- Blind people don’t have a ‘true’ constant environment
○ Meal times
○ Social cues
○ Conversations
○ Rest time
Have to be truly alone for constant environment
hors du temps
MICHEL SIFFRE (‘hors du temps’) - spent 2 months in a cave in scarasson and 6 months in a cave in Texas
· 24h for first month
· Then super chaotic
Days that lasted 18-52 hours
circadian rhythm in brain injury patients
24 hour circadian rhythm is an indicator of health in traumatic brain injury patients
what is the relation between homeostatic pressure and circadian rhythm
Circadian phase independent of homeostatic pressure - if u have a strong morning orientated circadian rhythm you will probs still wake up early even if you go to bed super late - tip have light blocking curtains
chronotype
Early bird/night owl? Morningness/eveningness
- Usually found out by ‘feeling’
- When do you like the wakeup, when do you like to go to bed?
- When do you do your best intellectual work
Subjective measure - varies with age and gender
early chronotype
better adapted to this life🐤🐦🐧🐦🐤🐤
- Migraines - correlation…no idea
- Consciensciousness
- Stability personality traits
‘nice grandma’ - wakes up early makes cookies does everything right
late chronotype
🦉🦉🦉🦉🦉🦉🦉🦉🦉🦉🦉🦉🦉🦉
- Addiction - smoking
- Nightmares
- Increased risk of depression
- Lower test grades - mismatch between late chronotype and school start
- Enhanced amygdala response
…is this intrinsic or societal?
taylor and hasler, 2023
Something instrinsic about late chronotypes…. Neural/psychological mechanisms
Altered reward process?
- Sensation seeking
- Impulsivity
- Cognitive biases
Impaired emotion regulation
societal explanation to taylor and hasler
Can these things also be explained by sleep deprivation/social jetlag? - not sleeping enough
Can’t go to bed but have to get up early
- Circadian misalignment
- Social jet lag ✈️
- Sleep loss
Disturbed sleep
can you change your chronotype
⭐️⭐️⭐️⭐️chronotype can’t be changed - just what you are
- Subjective feeling
- Established by trying to figure out when you feel better
Acute, punctual interruptions don’t really matter
issues with chronotype research
· Mixed chronotype
· Extreme phase delay
· Covid-19: some people able to reduce social jet lag
· Polyphasic sleep
○ 1st sleep and 2nd sleep
○ Old ancestors didn’t sleep a full night - animals don’t either
○ What is ‘natural’? We don’t know because polyphasic sleep doesn’t work in our social world
Most studies done of WEIRD populations
