Effect of membrane capacitance on the induced electric field for the magnetic peripheral nerve stimulation

Magnetic stimulation is an evolving, non-invasive neural stimulation technology used for clinical applications, including brain mapping, treatment of mood disorders, epilepsy, and chronic pain. Based on the induction principle, magnetic stimulation induces electric fields in the conductive tissue due to the time-varying current in the magnetic coil. It requires the magnetic coil to be in close proximity to the stimulation site to produce neural activation. The stimulation threshold of magnetic stimulation depends on the magnitude and the pulse width of the induced electric field. Traditionally, the efficacy of the magnetic stimulation is studied using analytical formulations based on the coil parameters and operating conditions (Roth, B. J. et. al., IEEE TBME 1990). Several studies were performed to include the tissue boundaries in the simulation model of the induced electric field (Nagarajan, S.S. et al., IEEE TBME 1996). However, these models were over simplified and do not include the tissue heterogeneity found in the nerve bundle.