Lecture 2

Methods in Sleep Research

• Retrospective: questionnaires

  • Pros: easy to get

  • Cons: often unreliable, subject to bias

• Prospective: sleep diaries

  • Pros: can be modified to target a specific sleep problem

  • Cons: labour-intensive, require motivation, captures limited subjective information

What are examples of retrospective and prospective subjective estimation and their pros and cons?

• Measures gross levels of motor activity

• Estimates sleep-wake patterns → sleep fragmentation

What is actigraphy?

• Pros: non-invasive, can be used at home

• Cons: records activity-rest patterns so limited sleep data

What are the pros and cons of actigraphy?

• Observing motor activity at night

• Pros: cheap

What function does video recording serves for studying sleep and what is its pros?

People who are sleep deprived so they fall asleep easily

Brain imaging is often done with which type of people?

• Uncomfortable

• Invasive

• Expensive

What are 3 cons of using brain imaging to study sleep?

• Measures hemoglobin concentration

• Pros: non-invasive, portable

What does functional near-infrared spectroscopy measures and what are its pros?

It measures heart rate variability and body temperature

An example of a portable EEG is “Oura”, but what does it measure?

• Record sleep patterns and are implanted for many day

What function do depth electrodes serve for studying sleep?

In the context of pre-operative or diagnostic epilepsy non-responsive to medication

In what context depth electrodes are used?

• Pros: very precise

• Cons: very invasive → only for animals

What are the pros and cons of single cell recordings?

Type	Measurement	Function
EOG	Eye movements	Categorize REM sleep or SWS
EMG	Muscle tonus	Detect REM sleep + diagnosis of sleep disorders
EKG	Heart rate	Diagnosis of cardiac anomalities in sleep
EEG	Brain’s electrical activity	Detect sleep onset, sleep stages and detection of anomalies

What are the 4 different types of polysomnography, their measurements and functions?

Type	Measurement	Function
EOG
EMG
EKG
EEG

• Amplitude: deviation from the baseline

  • Measures the synchrony of neurons

• Frequency: number of cycles per second

  • Measures the speed of discharge of neurons

What is the difference between amplitude and frequency of EEG waves?

EEG signal

Aggregated activity of thousands of pyramidal neurons perpendicular to the scull

No, there are multiple frequencies combined

In EEG, is there only 1 frequency present at all times?

dominant

In EEG, there is usually a ___________ frequency

Beta	Alpha	Theta	Delta
Wake	Resting wake, eyes closed	Sleep onset, NREM1, NREM2, REM	NREM3
13-30 Hz	8-13 Hz	4-8 Hz	0.5-4 Hz
Desynchronized: low amplitude			Synchronized: high amplitude

Which frequency bands (beta, alpha, theta, delta) are associated with each stages of consciousness/sleep?

Beta	Alpha	Theta	Delta

• Spatial resolution: location in the brain

• Temporal resolution: how quickly it can detect changes

What is the difference between spatial and temporal resolution?

Stages	%	Infos
Sleep onset	-	Gradual process Neurons stop firing for fractions of seconds
NREM1	5	General slowing of brain activity Eye movements - rolling Diminished responsiveness Hypnagogic imagery - sensations, images, sounds
NREM2	50	Mental activity range from simple to complex Presence of sleep spindles and K-complexes
NREM3	15	Brain activity is slow and synchronized Parasomnias (night terrors + sleepwalking)
REM	25	Mixed frequencies Muscle atonia/paralysis Rapid and saccadic eye movements 2 phases: tonic + phasic (eye movements) Breathing and cardiac activity are irregular Dreams + nightmares Realistic and engaging mental activity

What are the 5 sleep stages and their characteristics?

Stages	%	Infos
Sleep onset
NREM1
NREM2
NREM3
REM

• Sigma

• memory

• neurodegeneration

Sleep spindles:

• _________ activity

• Plays a role in ___________ consolidation

• Associated with protective processes against __________ and brain plasticity

• Bipolar

• cortical

• preserving

K-complex:

• ________ wave of 0.5 seconds

• Plays a role in thalamo-_______ gating

• Involved in _________ sleep

REM sleep

In which sleep stage does the face get completely relaxed?

Theta

The vast majority of sleep is in which frequency?

increases

The duration of REM sleep ___________ as the night passes

NREM3 because it is the most important

Which sleep stage is predominant during the 1st half of the night and why?

NREM3

If we wake up in this sleep stage, we feel confused and cranky

Yes they develop it

Do babies develop muscle atonia or are they born with it?