chronic electrode implants, the interface tissue between
the contact and the nerve changes due to development of encapsulation
tissues. With a proper cuff-fit and growth of encapsulation
tissues, model shows a change in the activation contours
(center of figure) from acute implants (without encapsulation,
left of figure) and from a loose cuff-fit (right of figure).
Effect of Contact Spacing
effect of distance between the contacts of the tripolar configuration,
3mm (left) and 6 mm (right) are shown in the figure. The
threshold was lowered with increase in contact spacing.
There was a shift in the activation contour of the 20 µm
axons for both the Jth and 2Jth values. The results appear
to show that smaller inter-contact distances are more efficient
in localizing the applied currents.
Anisotropy, perineurium and connective tissue were barriers
to the current flow between the electrode and the nerve fiber.
Perineurium and connective tissue decrease the selectivity
of excitation of specific regions of the nerve.
Anodic current from an electrode across from the cathode
improved the selective excitation of specific regions for
both monopolar and tripolar electrode configurations.
Tripolar electrodes provided greater selectivity than monopolar
Smaller spacing between the anodes and the cathode in a tripolar
configuration was more efficient in confining the current
to regions closer to the electrode.
Snugly fitting cuff reduced the scattering effect of the
saline layer present between the implanted cuff and the nerve.