Examination Of Nerve Fibers’ Membrane Potential Dynamics By Encoded Optical Second Harmonic Generation And Its Numerical Simulation

Nonlinear optical second harmonic generation imaging technology, with the characteristics of real-time, noninvasive and high quality imaging, could offer a novel method for examining the nerve fibers’membrane potential dynamics. In this thesis, we investigated the examination of nerve fibers’membrane potential dynamics by action-potential-encoded optical second harmonic generation and its numerical simulation. Firstly, we used finite element method to develop the models of action potential propagating along a nerve fiber, including unmyelinated and myelinated nerve fiber models. Secondly, nonlinear optical second harmonic generation combined with mathematical modeling was used to study the characteristics of action-potential-encoded optical signal and analyze the detected sensitivity of the method. And then we also used this method to investigate the fast detection of the information changes induced by the changes in morphology on a myelinated nerve fiber under a compression. Thirdly, we examined the demyelination of a myelinated fiber by second harmonic generation. Finally, we examined the second harmonic signals of dorsal root ganglion(DRG) neurons’membrane potential via laser scanning confocal microscope, and also proposed an improved multi-mode method to probe the nerve fibers’ membrane potential dynamics by optical second harmonic generation. The results showed that the membrane potential dynamics of a nerve fiber could be fast detected by action-potential-encoded second harmonic generation and the demyelination of a mylinatined nerve fiber could be examined via the changes of second harmonic generation signals of action potentials propagating along a nerve fiber by this method. The presented new method could real-time and fast detect optical signal and electrophysiology signal of nerve fibers’ membrane potential dynamics at once. It is shown that optical second harmonic generation is a potential tool for the clinical application in the field of neuroscience and neuropathology.