Current Density Profiles of Surface Mounted and Recessed Electrodes for Neural Prostheses

A Green's function approach has been used to solve Lapalce's equation for the quasi-static fields of a recessed, disk electrode. The resulting integral equation was solved numerically using the moment method. An analysis of the error in the approximate solution shows that it must be less than 7 percent for the cases studied. The calculations indicate that a recessed electrode has a more uniform current density profile than a surface mounted electrode. This is true both at the electrode surface, and at the electrode carrier-tissue junction. The significance of this finding is discussed as is its application to electrochemical, histopathological, and physiological studies of neural prostheses. The clinical use of recessed electrodes in cochlear implants is recommended.