circadian rhythms

Question 1

why are endogenous rhythms hard to study

Answer 1

because they are entrained - light, food social cues

we have to seriously mess up people’s routines to see what their natural circadian rhythms

Question 2

constant routine protocols

Answer 2

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)

Question 3

circadian rhythms

Answer 3

24 hour cycles (not just sleep)

Question 4

what do we measure to find out endogenous rhythms

Answer 4

melatonin and body temp

Question 5

how do we represent circadian rhythms

Answer 5

with waves - the distance between waves is the period - most people have a people of slightly longer than 24hours

Question 6

what three processes orchestrate sleep?

Answer 6

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

Question 7

what do we need to measure circadian period?

Answer 7

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

Question 8

what are the two competing needs of the circadian rhythm

Answer 8

Two competing needs: endogenous robust rhythm and able to adapt to environment

Question 9

what is free running

Answer 9

‘free running’ rhythms in constant conditions - means rhythms that are not synchronized by zietgeibers

Question 10

sleep in blind people

Answer 10

· Non 24 hour cycles
· Desynchronization from outside world
Weak effect of zeitgeiber entrainment - food/mealtime sometimes works but sometimes doesn’t

Question 11

examples of sleep structures in blind people

Answer 11

○ 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

Question 12

why don’t blind people have a true constant environment

Answer 12

• Blind people don’t have a ‘true’ constant environment
  ○ Meal times
  ○ Social cues
  ○ Conversations
  ○ Rest time
  Have to be truly alone for constant environment

Question 13

hors du temps

Answer 13

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

Question 13

circadian rhythm in brain injury patients

Answer 13

24 hour circadian rhythm is an indicator of health in traumatic brain injury patients

Question 14

what is the relation between homeostatic pressure and circadian rhythm

Answer 14

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

Question 15

chronotype

Answer 15

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

Question 16

early chronotype

Answer 16

better adapted to this life🐤🐦🐧🐦🐤🐤
- Migraines - correlation…no idea
- Consciensciousness
- Stability personality traits
‘nice grandma’ - wakes up early makes cookies does everything right

Question 17

late chronotype

Answer 17

🦉🦉🦉🦉🦉🦉🦉🦉🦉🦉🦉🦉🦉🦉
- 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?

Question 18

taylor and hasler, 2023

Answer 18

Something instrinsic about late chronotypes…. Neural/psychological mechanisms
Altered reward process?
- Sensation seeking
- Impulsivity
- Cognitive biases
Impaired emotion regulation

Question 19

societal explanation to taylor and hasler

Answer 19

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

Question 20

can you change your chronotype

Answer 20

⭐️⭐️⭐️⭐️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

Question 21

issues with chronotype research

Answer 21

· 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