Polarity Montages Localization

86 Pages·2013·9.38 MB·English

Polarity
Montages
Localization
Bassel Abou-Khalil, M.D.
I have no financial relationships
to disclose that are relative to the
content of my presentation
Learning Objectives
 to predict the appearance of potentials of
negative or positive polarity in different
montages
 to localize EEG potentials in referential and
bipolar recordings
 to build montages that are logical; identify the
advantages and disadvantages of bipolar and
referential montages; select the best
montages to characterize particular potentials
What is the polarity of the
transient demonstrated below
Positive
A.
Negative
B.
Fp1-F3
Either positive or
C.
negative
Neither
D.
Where is the most likely source
of this transient?
Fp1-F3 P3 and O1
A.
F3-C3
O1
B.
C3-P3
Fp1, C3, & P3
P3-O1 C.
What is the most likely polarity of
this transient?
Positive
Fp1-F3 A.
F3-C3
Negative
B.
C3-P3
Either positive
C.
P3-O1
or negative
Where is the center of the field?
C3 and P3
Fp1-F3 A.
F3-C3
C3
B.
C3-P3
F3
C.
P3-O1
Fp1
D.
The EEG
The EEG measures potential
differences between electrode positions
on the scalp.
Factors affecting scalp EEG
potentials
 Size, depth, orientation of generator/dipole
 Conductive properties of intervening tissues
 Duration of discharge
 Degree of synchronization
– Synchronous discharge over 10 cm2 cortex
surface area needed for spikes to show on scalp
 Propagation pattern
 Recording technique
Dipole orientation
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