Numerical estimation on the threshold of nerve excitation phenomena by the application of current with multiple frequencies based on Frankenhaeuser-Huxley model

摘要

International Commission on Non-Ionizing Radiation Protection (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 article is to estimate the threshold of nerve excitation caused by the application of current with multiple frequencies. In this article, combinations of two kinds of frequencies f_1 and f_2 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 f_1 and f_2, respectively. Consequently, the threshold did not exceed if the philosophy of the addition equation of International Commission on Non-Ionizing Radiation Protection (ICNIRP) was satisfied, with any combination of f_1 and f_2 analyzed in this article. Especially when f_1 - 2f_2 andf_2 = 2f_1 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 f_1 = 2f_2 and f_2 = 2f_1.