Fig. 5.

Comparison of electric field distribution measured axially at the interface between the peri-electrode space and the surrounding tissue during (a) monopolar and (b) bipolar stimulation. Three situations are shown: (i) with a layer of ECF in the peri-electrode space; (ii) with no peri-electrode space at all; (iii) when the space is filled by the growth of giant cells. The quantitative difference between the induced field strengths are shown in (c), for both monopolar and bipolar stimulation, in three cases: (i) homogenous tissue compared to including a ECF layer; (ii) homogenous tissue compared to including a layer of giant cells; (iii) comparing an ECF layer to a giant cell layer. These percentage changes show that the content effect of the peri-electrode space on the induced electric field is greater in bipolar stimulation than monopolar stimulation.