Effects of the electrical double layer and dispersive tissue properties in a volume conduction model of deep brain stimulation

The aim of this study was to investigate the interaction of the electrode-tissue interface and dispersive tissue properties on waveforms used for deep brain stimulation. A finite element model with a distributed impedance electrical double layer was developed. Bulk tissue capacitance and dispersion were found to alter the voltage waveform under constant current stimulation. When the electrode was surrounded by conductive saline or white matter tissue, the electrical double layer was dominant under voltage controlled stimulation. However, as encapsulation tissue resistivity was increased, to emulate chronic stimulation, the voltage waveform approached that observed during constant current stimulation and the influence of the frequency dependent material properties again became dominant.