Simulation of Spatiotemporal Current Density Distribution on Electrode-Electrolyte Interface during Deep Brain...

The current density distribution on deep brain stimulation (DBS) electrodes can affect tissue damage, electrode corrosion, and the patterns of excitation generated in the tissue. The current density distribution can be influenced by the impedance of the electrode-electrolyte/tissue interface. The objective of this research is to investigate the effect of the electrode-electrolyte interface on the spatiotemporal current density distribution on DBS electrodes in response to DBS pulses. We implemented a finite element model of a monopolar DBS electrode that incorporated a representation of the electrode-tissue interface by inserting interface impedance measured from electrochemical impedance spectroscopy. An interface model was developed to account for the nonlinearity of impedance with current density, and simulation of the spatiotemporal pattern of current density was performed by decomposing a clinical-relevant biphasic pulse into its harmonic frequency components. The results indicate that the spatiotemporal pattern of current density resembled the highly non-uniform primary current density distribution upon onset of the primary phase, and the current densities decreased quickly during the pulse, suggesting that the stimulation efficiency of excitable tissue occurs primarily at the beginning of the primary pulse towards the edges of the metal contacts.