Finite element modeling of the neuron-electrode interface: sealing resistance and stimulus transfer at transitions from complete to defect sealing

The quality of the electrical contact between a cultured neuron and a substrate embedded microelectrode is of importance for effective transfer of an extracellular applied stimulus current to the intracellular potential. It is affected by the resistance of the seal, i.e. the gap between the cell membrane and the substrate, which restricts the leakage current, thereby favouring the efficiency of the stimulation current. The effects of variations in the geometry of the neuron-electrode interface on the sealing resistance and on the stimulus transfer are studied using a finite element model of this interface. Variations in the geometry of the neuron-electrode interface are represented by the eccentricity, x_c, of a pillbox shaped neuron with radius r_c, cultured on an electrode with radius r _c. The results indicate a sharp decrease in both sealing resistance and stimulus transfer when a transition occurs from complete sealing to defect sealing. At that point the leakage current splits up into a current through the gap and a current through the sealing defect