User Manual
Table Of Contents
3. EEG/PSG MEASUREMENT
Operator's Manual WEE-1000 3.7
Introduction to Electrode
Position, Derivation and
Montage
F
3
F
4
F
8
F
7
F
P1
F
P2
F
Z
C
Z
P
Z
P
3
P
4
C
4
C
3
T
3
A
2
A
1
T
4
T
6
T
5
O
2
O
1
13
3
1
2
19
4
14
12
16
6
24
20
8
18
5
7
17
15
11
9
10
Nasion
Inion
10-20 system electrode positions
Electrode Position
There are various systems of electrode position, such as Illinois, Montreal, Aird,
Cohn, etc. Of these, the International 10-20 system, shown below, is currently the
most common. Each system has a different number of electrodes and different
electrode locations. To compensate for different sized heads, the distances between
electrodes are given as ratios.
After determining the electrode position system, measure the head of the patient
and calculate the electrode positions according to the distance ratio between each
electrode position. The number of electrodes should be reduced for EEG recording
on infants and little children.
Derivation
Derivation is the electrode combination for one channel. All derivations have two
electrodes: reference and active. In monopolar derivation, one “electrode” can be
several physical electrodes connected together. There are 3 kinds of derivations.
Monopolar Derivations (Referential Derivation)
In the monopolar derivation, one electrode is common to all channels and regarded
as electrically inactive (“reference electrode”). Each amplifier has two inputs (G1
and G2). The reference electrode is connected to the G2 (+) input of the amplifier
and the active electrode is connected to the G1 (−) input.
Monopolar Derivations Using Ear Reference Electrodes:
• Normal Monopolar Derivation
Left ear for left hemispheric derivation and the right ear for right hemispheric
derivation.
• A1 + A2
Shorting both ears (in the electrode junction box).
• A1 → A2 or A1 ← A2
Only one ear.
• A1 ↔ A2
Left ear for right hemispheric and right ear for left hemispheric derivation.