Introduction lecture
Disadvantage of sleep: when you sleep you don't get what is going on around
you (so you are an easy target for predators) → thus, sleep must be very very
important if we still do this even if it is so dangerous
- some animals, like dolphins, only sleep with one hemisphere at a time (can be seen
in EEG)
- sleep time does not depend on brain size or species
Reason why some animals sleep more?
- for carnivorous animals: weight does not matter for sleep time
- for herbivorous animals: weight is negatively correlated to sleep time → fat
animals like elephants eat all day to get all the nutrients they need so they
sleep very little
→ if you can afford to sleep a lot (you don't need to eat all day), you do sleep a
lot
,→ ways to see if an animal is sleeping without EEG/polysomnography (which is
the gold standard in humans)
Polysomnography
- most important measurement is the EEG (measure currents between
pyramidal neurons in the cortex) → if they are unsynchronically active
there is alpha activity (fast pattern), if they fire synchronically (all at the
same time) there are delta waves (long, slow waves)
- helps determine the sleep stage:
- breathing is also often measured (as sleep apnea is one of the most occurring sleep
disorders next to insomnia), but EEG, EOG and EMG are the most important
measurements
Sleep stages
● wakefulness: eyes open (blinks), lot of EMG movement, beta rhythm (13-30Hz)
● NREM1: mainly at beginning of the night, slow eye-rolling (SEM), slowing EEG
(disappearing of alpha), less muscle activity but still some
● NREM2: stable sleep, no eye movement, sleep spindles, and k-complexes in
EEG
, ● NREM3: deep sleep/ slow-wave sleep, delta oscillations (~4Hz)
● REM: EEG looks like awake person EEG , rapid eye movement, muscle atonia
(paralyzed)
Sleep oscillations
- we normally measure between slow (1HZ) and beta (20Hz)
- sleep oscillations are nested in other oscillations (ripples in gamma, gamma in beta,
etc.)
Sleep cycles
- more Rem sleep at the end of the night, more deep sleep at the beginning of the
night
- sleep stages/hypnograms change over the lifespan
Two process model
- model of sleep regulation
- Process C (circadian oscillations) and process S (sleep pressure)
Disadvantage of sleep: when you sleep you don't get what is going on around
you (so you are an easy target for predators) → thus, sleep must be very very
important if we still do this even if it is so dangerous
- some animals, like dolphins, only sleep with one hemisphere at a time (can be seen
in EEG)
- sleep time does not depend on brain size or species
Reason why some animals sleep more?
- for carnivorous animals: weight does not matter for sleep time
- for herbivorous animals: weight is negatively correlated to sleep time → fat
animals like elephants eat all day to get all the nutrients they need so they
sleep very little
→ if you can afford to sleep a lot (you don't need to eat all day), you do sleep a
lot
,→ ways to see if an animal is sleeping without EEG/polysomnography (which is
the gold standard in humans)
Polysomnography
- most important measurement is the EEG (measure currents between
pyramidal neurons in the cortex) → if they are unsynchronically active
there is alpha activity (fast pattern), if they fire synchronically (all at the
same time) there are delta waves (long, slow waves)
- helps determine the sleep stage:
- breathing is also often measured (as sleep apnea is one of the most occurring sleep
disorders next to insomnia), but EEG, EOG and EMG are the most important
measurements
Sleep stages
● wakefulness: eyes open (blinks), lot of EMG movement, beta rhythm (13-30Hz)
● NREM1: mainly at beginning of the night, slow eye-rolling (SEM), slowing EEG
(disappearing of alpha), less muscle activity but still some
● NREM2: stable sleep, no eye movement, sleep spindles, and k-complexes in
EEG
, ● NREM3: deep sleep/ slow-wave sleep, delta oscillations (~4Hz)
● REM: EEG looks like awake person EEG , rapid eye movement, muscle atonia
(paralyzed)
Sleep oscillations
- we normally measure between slow (1HZ) and beta (20Hz)
- sleep oscillations are nested in other oscillations (ripples in gamma, gamma in beta,
etc.)
Sleep cycles
- more Rem sleep at the end of the night, more deep sleep at the beginning of the
night
- sleep stages/hypnograms change over the lifespan
Two process model
- model of sleep regulation
- Process C (circadian oscillations) and process S (sleep pressure)
