Effects of the Extracellular Electrical Stimulation on the Excitability of Optic Nerve Fibers by Mathematical Modeling
1 School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
2 Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, China
Abstract A visual prosthesis based on penetrating electrode stimulation within the optic nerve (ON) is a potential way to restore partial functional vision for the blind patients. In order to provide theoretical basis for electrical stimulation strategies and the electrode design of abovementioned visual prosthesis, a finiteelement model of the electric field generated by an actual penetrating microelectrode was constructed in COMSOL, and then coupled to the multicompartment cable model of the optic nerve fiber implemented using NEURON. With this method, we evaluated the effects of stimulating electrode location, pulse duration of electrical stimulus and electrode structure on the excitation thresholds of optic nerve fibers. Simulation results showed that the impact of the former two factors on the fiber thresholds agreed with that reported in previous animal and simulation studies, which demonstrated the effectiveness of our models. The following suggestions about the design of stimulus pulse duration and electrode structure of the penetrative ON prosthesis were also obtained according to our simulation work. Stimulus with narrow pulse width helps reduce energy consumption. The electrode taper should be designed as small as possible to lower the threshold but should not disturb the electrode insertion. Decreasing the electrode exposed area helps lower the current threshold and therefore reduces the power consumption, but it also increases the charge density threshold, which eases to result in electrochemical damage to ON. Thus, the electrode exposed area should be designed appropriately to avoid excessive power consumption and tissue damage. Changing the coating thickness of the electrode has no significant effect on the fiber threshold, but a electrode with thin coating is recommended to decrease the insertion difficulty. These results are also of valuable reference to the electrical stimulation of other nerve fibers of human body.
GUO Hong1 SUI Xiao Hong1 LI Meng Hui2 LI Li Ming1*. Effects of the Extracellular Electrical Stimulation on the Excitability of Optic Nerve Fibers by Mathematical Modeling[J]. journal1, 2014, 33(5): 574-584.
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