1. Polysomnography & Sleep Scoring
John Shaw
Lancaster University

2. Procedure Before they turn up
Instructions to participants
Try to have a relaxed day- No daytime sleep
Wash their hair!
Prepare the material
Prep gel
Electrodes
Gauze/tape
Hair clips
Computer set up

3. 10 - 20 System Widely used, standardised system of electrode placement
Electrodes placed at specific intervals along the head
Each spot has an identifying letter and a number.
F- Frontal
T- Temporal
C- Central
P- Parietal
O- Occipital
z- Mid line
Odd Numbers- Left Hemisphere
Even Numbers- Right Hemisphere

5. Landmarks

6. 10 – 20 System Nasion- depressed area between the eyes
Inion- prominent projection of
occipital bone

7. 10 – 20 System FPz- 10% above the Nasion
Fz, Cz, Pz and Oz at 20% interval
Leaves 10% between Oz & the Interval

8. 10 – 20 System Measure between the two preauricular points across Cz
10% up from Ax is Tx, 20% up from Ax is Cx

9. 10 – 20 System
Circumference of the head is measured through Fpz, Oz, T3 and T4

10. 10 – 20 System
Circumference of the head is measured through Fpz, Oz, T3 and T4
5% from Fpz is Fp1/Fp2
10% from Fp1/Fp2 is F7/F8
10% from F7/F8 is T3/T4
10% from T3/T4 is T5/T6
10% from T5/T6 is O1/O2
5% from O1/O2 Is Oz 5%
10%
10%
10%
10% 5%

11. 10 – 20 System
Longitudinal distance from Fp1/Fp2 through C3/C4 to O1/O2 is measured either side at 25% intervals
25%
25%
25%
25%

12. 10 – 20 System
F7 through to F8, passing through F3, Fz, and F4 at intervals of 25%
25%
25%
25%
25%

13. Got the key 6 points
A1 & A2 are positioned on the ear lobe or the mastoid
Ground electrode placed on FPz

14. System

15. Electrode Application
Prepare the Electrode site
Thorough cleaning to remove dirt/debris/dead skin cells
Use of Electrically conductive prep solution
Preparing the Electrode
Sterilized after the previous study
Filled with electrically conductive paste, filling the cup

16. Electrode Application
Placing the Electrode
Placed in the exact location of the mark
Hair clips are useful
All sides of the metal cup should be in contact with the skin
Applying the Electrode
Place gauze diagonally over the cup with small amount of tape holding it down

17. Impedance Checks Impedances are measures of electrical resistance
High impedance = signal distortion
Maximum electrical impedance should be 5000 Ohms
If over this, remove sensor and go through the steps again

18. Sleep Scoring

19. Sleep Scoring Monitor the 8 channels outlined earlierF3 F4 C3 C4 O1 O2
M1 (Reference)
M2 (Reference)
Paper speed of 10mm/Sec, defined as an Epoch
Standard studies only need 3 channels, having 6 ensures a backup

20. Sleep Scoring Rechtschaffen and Kales (1967)
Introduced a manual for sleep scoring for different stages

21. Sleep Stages Stage W NREM (70-80%) REM (20-25%)
SWS (15-20%)
REM (20-25%)
Sleep starts with NREM, enters REM sleep after about 60 mins
NREM-REM cycles every 90 mins
Typically 4-6 cycles per major sleep episode
Sleep qualitatively changes during the night

23. Sleep Scoring- Stage W Participant is awake
Movement artifacts obscure most behaviour
Occipital channels display alpha activity when eyes are closed

24. Sleep Scoring- Stage N1
Low voltage, mixed frequency EEG pattern, typically 4-7Hz
First sleep stage entered from Wakefulness
The ‘Transitional stage’
People can still hear noises in the room and think they are awake
Experience of little sleep when actually you have

25. Sleep Scoring- Stage N2
Comprises about 50% of total sleep time in healthy adults
N2 is characterised by the presence of sleep spindles and K complexes and begins at the first instance of sleep spindles or K complexes
Absence of slow waves

26. Sleep Scoring- Spindles & K-complexes
Brief bursts of activity appearing in the central channel
Most commonly associated with Stage N2 sleep
Associated with transference of memories from the hippocampal store to the neocortex in consolidation of skills
K-complexes
Sharp negative wave followed by a slower positive component

27. Sleep Scoring- Stage N3
Replaces delta sleep (Stages 3 & 4) from Rechtschaffen & Kales
Epoch is scored as N3 when at least 20% contains slow waves
Typically be between 0.5-2Hz in frequency, prominently seen in frontal/central locations
Most often seen during the first third of the night, reducing progressively

28. Sleep Scoring- Slow Waves
Low Frequency, high amplitude waves typically seen in the frontal region

29. Sleep Scoring- Stage R
REM sleep is highly beneficial for memory restoration.
Typically occurs 90 mins after sleep onset
Initially quite short but progressively gets longer as night progresses
Presents similar frequencies to N1
Sawtooth waves typically 2-6Hz
After 1 instance of Stage R, all subsequent epochs are coded the same until spindles/K-Complexes are present

30. Polysomnography & Sleep Scoring
John Shaw
Psychology Department
Lancaster University
If anybody wishes to use or reproduce any materials in the presentation please credit the original author.