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HC1: The rhythm of the night
Date @02/06/2025
courses 😴 Slaap
College
1. What is sleep?
Periodic (reversible and temporary) state of less reactivity to external stimuli
Highly versatile
Across species: Special sleepers like koalas, dolphins, otters
Across individuals
Healthy sleep between 6-9 hours
Natural short sleepers are very rare
4-6 hours a night
No cognitive aversive affects
Maybe related to genetic mutations that are involved in the biological clock.
1. Why do we sleep?
1. Evolution: being inactive at night has a survival function
But being unconscious is not safe
2. Energy saving: drop in O2 need, heart rate, breathing frequency and temperature → lower metabolism
3. Restoration theory
Deep sleep stimulates the immune system
Anabolic period: growth hormone, cell division, protein synthesis > protein degradation
4. Brain plasticity
Relation between sleep and changes in structure and organization of the brain
HC1: The rhythm of the night 1
, Sleep is important for brain development in babies and children
Sleep is important for memory consolidation in adults
2. Sleep & daytime functioning
Sufficient sleep is needed for alertness, coping with stress, information processing & melody consolidation and
attention/concentration
Long-term/larger effects: less chance of diabetes, cardiovascular diseases, obesity, and depression. It flushes toxic
waste from the brain and boost of immune system
2. How to measure sleep
1. Actigraphy
= measure of movement
✅ Non-invase and simple method
⛔ Rough measure: cannot detect wakefullness during sleeping
2. Polysomnography
Sleep stage scoring
EEG: brain waves
EOG: Eye movemenst
EMG: muscle tension
More measures to determine sleep disorders
Respiratory movement (thorax, abdomen)
Air exchange nose/mouth
Oxygen saturation
Limb movements
3. Sleep structure
HC1: The rhythm of the night 2
, 1. Stages
Frequencies:
Sleep stages (American Academy of Sleep Medicine AASM)
1. Wake
2. NREM-sleep: light (N1 and N2) and deep (N3)
3. REM-sleep
2. Wake
EEG: desynchronized activity between 8-40 Hz
rest, eyes closed: 7.5-12 Hz (alpha)
EOG: many eye movements and eye blinks
EMG: high muscle tension
3. Transition to sleep
EEG: transition of alpha (7.5-12 Hz) to theta (4-7 Hz)
EOG: sometimes slow, rolling eye movements
EMG: Quite high muscle tension
HC1: The rhythm of the night 3
, 4. Stage 1
EEG: Mixed activity of alpha and theta, vertex waves
EOG: Sometimes slow, rolling eye movements
EMG: Quite high muscle tension
5. Stage 2
EEG: Theta activity (4-7 Hz), sleep spindles (12-14 Hz), K-complexes
EOG: Quiet
EMG: Average muscle tension
6. Stage 3
EEG: Slow oscillations (0.5 - 2Hz) with a high amplitude
EOG: Quiet
EMG: Somewhat lower muscle tension
HC1: The rhythm of the night 4
HC1: The rhythm of the night
Date @02/06/2025
courses 😴 Slaap
College
1. What is sleep?
Periodic (reversible and temporary) state of less reactivity to external stimuli
Highly versatile
Across species: Special sleepers like koalas, dolphins, otters
Across individuals
Healthy sleep between 6-9 hours
Natural short sleepers are very rare
4-6 hours a night
No cognitive aversive affects
Maybe related to genetic mutations that are involved in the biological clock.
1. Why do we sleep?
1. Evolution: being inactive at night has a survival function
But being unconscious is not safe
2. Energy saving: drop in O2 need, heart rate, breathing frequency and temperature → lower metabolism
3. Restoration theory
Deep sleep stimulates the immune system
Anabolic period: growth hormone, cell division, protein synthesis > protein degradation
4. Brain plasticity
Relation between sleep and changes in structure and organization of the brain
HC1: The rhythm of the night 1
, Sleep is important for brain development in babies and children
Sleep is important for memory consolidation in adults
2. Sleep & daytime functioning
Sufficient sleep is needed for alertness, coping with stress, information processing & melody consolidation and
attention/concentration
Long-term/larger effects: less chance of diabetes, cardiovascular diseases, obesity, and depression. It flushes toxic
waste from the brain and boost of immune system
2. How to measure sleep
1. Actigraphy
= measure of movement
✅ Non-invase and simple method
⛔ Rough measure: cannot detect wakefullness during sleeping
2. Polysomnography
Sleep stage scoring
EEG: brain waves
EOG: Eye movemenst
EMG: muscle tension
More measures to determine sleep disorders
Respiratory movement (thorax, abdomen)
Air exchange nose/mouth
Oxygen saturation
Limb movements
3. Sleep structure
HC1: The rhythm of the night 2
, 1. Stages
Frequencies:
Sleep stages (American Academy of Sleep Medicine AASM)
1. Wake
2. NREM-sleep: light (N1 and N2) and deep (N3)
3. REM-sleep
2. Wake
EEG: desynchronized activity between 8-40 Hz
rest, eyes closed: 7.5-12 Hz (alpha)
EOG: many eye movements and eye blinks
EMG: high muscle tension
3. Transition to sleep
EEG: transition of alpha (7.5-12 Hz) to theta (4-7 Hz)
EOG: sometimes slow, rolling eye movements
EMG: Quite high muscle tension
HC1: The rhythm of the night 3
, 4. Stage 1
EEG: Mixed activity of alpha and theta, vertex waves
EOG: Sometimes slow, rolling eye movements
EMG: Quite high muscle tension
5. Stage 2
EEG: Theta activity (4-7 Hz), sleep spindles (12-14 Hz), K-complexes
EOG: Quiet
EMG: Average muscle tension
6. Stage 3
EEG: Slow oscillations (0.5 - 2Hz) with a high amplitude
EOG: Quiet
EMG: Somewhat lower muscle tension
HC1: The rhythm of the night 4
