Nerve Signal Propagates in the Mid-Infrared to Terahertz Spectral Range by a Mechanism Consistent with Ephaptic Coupling

Understanding of the nerve signal propagation mechanism for the myelinated nerve fiber could contribute to the improved diagnosis and medical treatment of demyelinated nerve diseases. The existing nerve propagation models have gaps in their explanation of the role of myelin sheath in the nerve signal transmission process. In our hypothesis, we propose that the myelin forms a dielectric waveguide for the nerve signal to propagate non-synaptically via an electromagnetic wave transmission mechanism. In our study, we model the myelinated nerve fiber using experimentally-obtained optical parameters, and then reproduce the experimental study of ephaptic coupling through a nerve slice through an electromagnetic full-wave simulation. The waveguide propagation performance of the nerve signal is studied within the mid-infared and terahertz spectrum, and ephaptic coupling performance is studied for different separation gaps between two nerve fibers. It is expected that the study will provide a better understanding of the nature and experimental observation of wave propagation and ephaptic coupling through a nerve fiber.