Biomedical Engineering Reference
In-Depth Information
d
n
4
t
3
n
g
|
2
n
3
.
Figure 6.2
Equivalent electrical circuit for a neural axon.
16
(Reprinted with kind permission of the International Federation of
Clinical Neurophysiology.)
Figure 6.3
Electrical circuit model for the electrode-tissue interface.
16
(Reprinted with kind permission of the International Federation of
Clinical Neurophysiology.)
The implanted electrode is not a perfect source of voltage or current and the
surrounding tissue is not a perfect conductor as it is shown in the model.
Electrode effects and tissue capacitance must be carefully considered in order
to avoid spatial errors as small as 1mm for activation, which can lead to
dramatic consequences for the patient. The electrical circuit model for the
electrode-tissue interface is presented in Figure 6.3 where C
dl
is the double-
layer capacitance of
the electrode,
in parallel with the simplified tissue
impedance (R
tissue
and C
tissue
).
Fourier finite element methods are used to study and evaluate the effects of
the tissue and electrode properties on the volume of activated tissue during deep
