Numerical Estimation on the Threshold of Nerve Excitation Phenomena by the Application of Current with Multiple Frequencies based on Frankenhaeuser-Huxley Model

Abstract

ICNIRP guidelines describes addition equation for electrical stimulation, relevant for frequencies up to 10 MHz, with respect to simultaneous exposure to magnetic fields with multiple frequencies. However, there is no literature which estimated the threshold of electromagnetic field exposure of multiple frequencies. Therefore, the purpose of this paper is to estimate the threshold of nerve excitation caused by the application of current with multiple frequencies. In this paper, combinations of two kinds of frequencies f₁ and f₂ were investigated for the applying current. The Frankenhaeuser-Huxley model was employed to analyze nerve excitation effects. The ratios of the applied current value to the threshold current value were kept at the same value for each frequency f₁ and f₂, respectively. Consequently, the threshold did not exceed if the philosophy of the addition equation of ICNIRP was satisfied, with any combination of f₁ and f₂ analyzed in this paper. Especially when f₁=2f₂ and f₂=2f₁, the threshold became a high value. By analyzing the amount of the accumulated electric charge, which is a factor causing the action potential, it was demonstrated that it is difficult to accumulate the electric charge when f₁=2f₂ and f₂=2f₁.