Effects of Microelectrode Array Configu- Ration and Position on the Threshold in Electrical Extracellular Stimulation of Single Nerve Fiber: a Modeling Study

A transient finite-element model has been presented to simulate extracellular potential stimulating in a neural tissue by a nonplanar microelectrode array (MEA). This model allows simulating the extracellular potential and transmembrane voltage by means of a single transient computation performed within single finite element (FE) software. The differential effects of the configuration and position of MEA in electrical extracellular stimulation are analyzed theoretically. 3-D models of single nerve fiber and different MEA are used for the computation of the stimulation induced field potential, whereas a cable model of a nerve fibre is used for the calculation of the transmembrane voltage of the nerve fiber. The position of MEA and the spacing of the microelectrodes are varied while mono-, bi-, tri-, and penta-polar MEAs are applied. The model predicts that the lowest stimulation voltage threshold is obtained in the stimulation with penta-polar MEA. Moreover, the relationships, which exist between the thresholds of the electrical extracellular stimulation and the parameters including position of the electrode array and the spacing of the microelectrodes in array, are studied and obtained.