Modeling the activation of a non-homogenous nerve fiber by magnetic stimulation

In this paper we present a model that combines circuit analysis with Maxwell´s equations of electromagnetic theory and non-linear cable theory, to explain the action of the induced electric field upon a nerve fiber. The current source and stimulating coil are modeled as a series RLC circuit. The induced electric field distribution within a homogeneous cylindrical volume conductor modeling the arm is calculated for different time courses of the current. The effect of the induced electric field upon the nerve is determined with a cable model which contains active Hodgkin-Huxley elements. The possible non-homogeneities of the nerve´s electrical properties are also considered, and we assess their influence on the activation of the nerve.