A Theoretical Research Of The Mechanism Of Infrared Neural Stimulation

Infrared neural stimulation(INS)is a new technology of nerve stimulation that is being researched in recent years.It is a new method of nerve stimulation using infrared light instead of traditional energy sources and it is a branch of neurophotonics.INS is different from the traditional nerve stimulation,with high resolution,low damage,non-contact and other significant advantages in clinical neurobiology research has broad application prospects.Infrared lasers(780-3000 nm)have unique advantages in neural stimulation due to their optical and spatial accuracy.Compared with the traditional electrical stimulation,INS uses fiber-coupled laser to stimulate the nerve tissue and avoid the possible mechanical damage caused by the contact electrode in the electrical stimulation method.In the meantime,the space precision of the laser beam stimulation is good,which can stimulate a specific area of neurons without a range effect.But in the aspect of safety,INS uses photothermal as stimulus,so it is necessary to control the safe threshold of laser energy that stimulates sufficient intensity of neural response without thermal damage to nerve tissue.However,the physical experiment of infrared neural stimulation requires many strict conditions.First,we must maintain the biological activity of the living nerve tissue.Second,it needs an external device to measure the nerve action potential of the tissue,and it is hard to measure the energy flow with in the nerve tissue.Overall,the experimental cost is very high.At the same time,the theoretical analysis of the process of infrared neural stimulation is limited,it is difficult to solve the transmission rule of infrared light energy inside the nerve tissue just by using mathematical analysis method,and it is impossible to accurately acquire the relationship between the infrared light parameter and the stimulation result.In this research,we take the infrared neural stimulation as the experimental background,and the Monte Carlo method based on probability and statistics was used to simulate the behavior of photons in tissue during INS.The purpose of this study is to derive the parameters of infrared neural stimulation(such as the number of photons,the radius of exposure plane,launch mode of photons,etc.)and the degree of photothermal reaction of nerve tissue,in particular the spatial nature of the heat flow inside the tissue after the infrared light irradiates the nerve tissue.The trajectories of a large number of photons are tracked one by one by the numerical simulation of the model,then the spatial distribution of photon absorption is recorded,and the macro energy distribution generated by the infrared light nerve stimulation is recorded.Further more,we can acquire the data of the penetration depth,the spatial localization of the infrared light and the temperature gradient distribution in the tissue.Based on these results,we can make theoretical guidance to the experimental research and cut the high cost of the experiment of INS.