Optimization of simulated RLC circuit and solenoid coils used in the magnetic stimulation of rat sciatic nerves

Magnetic stimulation, as a means of evoking neuromuscular activity, has an advantage over direct electrical stimulation in that the stimulator need not directly contact the neural tissue. However, the high energy levels and large magnetic coils needed to elicit a response hinder the use of implantable magnetic stimulators for functional neural stimulation. Our group has previously reported a µm-scale computational model that quantifies the neurostimulation efficacy of a time-varying magnetic field on the myelinated axons of rat sciatic nerve, where discharging the voltage stored on a capacitor through an air-core solenoid coil creates the field. Further, we have validated the performance of this model with in vivo experiments in the rat using a small sample of solenoid coils, and we have observed that solenoid coils with ∼1cm³ volumes can evoke neural excitation with discharge voltages as low as 110 V. In this work, we report on using the computational model to optimize the stimulation system and the solenoid coil design to reduce the discharge voltage necessary to evoke neural activity (i.e., threshold voltage).