Selective Activation – Animal Experiments

Experimental Findings (field steering)


To this point, Tarler has shown us that the recruitment characteristics for a monopolar snug-fitting-cuff electrode are very similar to that found with the tripolar electrode configuration. And, recall that the current flow patterns are similar for the two configurations; particularly so when the length of the cuff is short. Also, as a reminder, the advantage to the monopolar cuff is that there are fewer lead wires and connectors in the monopolar configuration.
A surprising finding from Tarler was that it was easy to modulate the activation of fibers in a single fascicle from threshold to full activation. What then follows is the question, Is it possible to activate selectively and independently any of the four motor fascicles in the sciatic nerve with a four contact self-sizing spiral cuff electrode?
This is where field steering will come into play. In one case the medial gastrocnemius fascicle could not be activated with a single contact, and in the other case the medial gastroc branch and the tibial branch were recruited together from the single contact.
It is important to note, that in these experiments there was no effort to try to align a contact with any specific branch. The self-sizing-spiral cuff was placed on the nerve, only, with consideration given to how the lead wires were positioned to minimize mechanical irritation to adjacent tissues.