Current-Distance Relations for Monopolar Electrodes and for Ring Electrodes

Abstract

For many applications using implanted electrodes, it is important to know how many fibers can be activated by a given current signal. A simple rule is: distant fibers need stronger currents in order to be stimulated, and also the number of firing fibers increases with the strength of stimulation signal. Fig. 8.1 illustrates the current-distance relation from several experiments which were gathered by Ranck (1975). Because there are differences in the original experiments, other durations of current impulses are considered by a correcting factor. The dashed line shows the calculated relation with the assumption that the electrode lies just above a node. Simulation was done with equations 7.2, 7.5 and the Frankenhaeuser-Huxley model.