局所的磁気刺激における神経線維の興奮閾値

抄録

Focal magnetic stimulation using a figure-of-eight coil is a useful method to investigate the intact nervous system. Analytical studies using models of magnetic stimulation of a nerve fiber indicate that the nerve fiber is stimulated by the gradient of the component of the induced electric field that is parallel to the fiber. Theoretically, the nerve fiber which is parallel to the induced electric field has the minimum threshold for the excitation. However, some experimental studies show that the nerve bundle perpendicular to the induced electric field, which is parallel to the wings of the figure-of-eight coil, has the minimum threshold for eliciting the muscle response. In this study, the reason for this inconsistency between the theoretical results and the experimental results is explained using an analytical model. It is verified that the threshold for the excitation of the nerve fiber which is parallel to the wings of figure-of-eight coil is lower than that of nerve fiber parallel to the coil wings when the nerve fiber is away from the center of the coil at some distance.