Durand D, Ferguson A S, Dalbasti T
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106.
IEEE Trans Biomed Eng. 1992 Jan;39(1):58-64. doi: 10.1109/10.108128.
The effect of the surface boundary between free space and a conducting medium on the excitation properties of neurons by magnetic fields are analyzed. The electric field and the spatial derivative of the induced field generated by a coil mounted both parallel and perpendicular to the surface of a semi-infinite conducting medium were calculated using the method of images. An imaginary axon is located in the same relative position from the coil in both configurations and the excitation properties are compared. The calculations are expressed in terms of the activating function for the electrical stimulation of axons. The calculations indicate that the activating function for magnetic stimulation is biphasic as opposed to triphasic for electrical stimulation. The large spatial extent of the magnetically induced electric field compared to the electric field generated by point source electrode suggests a different mode of excitation for neuronal structures in the CNS. The field distribution have been verified experimentally and are important for the understanding of the mechanisms of magnetic stimulation of neural tissue.
分析了自由空间与导电介质之间的表面边界对磁场激发神经元特性的影响。使用镜像法计算了与半无限导电介质表面平行和垂直安装的线圈所产生的电场和感应场的空间导数。在两种配置中，假想轴突都位于距线圈相同的相对位置，并比较了激发特性。计算结果以轴突电刺激的激活函数表示。计算表明，磁刺激的激活函数是双相的，而电刺激是三相的。与点源电极产生的电场相比，磁感应电场的空间范围较大，这表明中枢神经系统中神经元结构的激发模式不同。场分布已通过实验验证，对于理解神经组织的磁刺激机制很重要。
