Simulation Of Action Potential Of Rgcs Based On HH And FCM Models

Artificial retina is one of the most popular research projects in the field of biomedicine,and the current research is mainly aimed at improving the resolution and biocompatibility of artificial retina.The electrode array on the artificial retina can emit electrical stimulation to activate neuronal function.Retinal ganglion cells（RGC）are the only neurons in the retina that can generate action potentials.The action potentials generated by them have the characteristics of digital signals,and they can transmit information without attenuation through the myelin sheath and nodes of Ranvier on the nerve fibers.Therefore,it is particularly important to study the response of optic ganglion cells to electrical stimulation.Currently,in experiments on RGC,the cell body is often used as the stimulation target to study the effects of current type,current intensity,electrode depth,and other factors on action potential.However,there are few studies on the effects of different types of electrical stimulation on action potential and comparing the emission characteristics between cell body and axon hillock.Based on the Hodgkin-Huxley（HH）and Fohlmeister-Coleman-Miller（FCM）models,a simulation program is established in MATLAB to simulate the response of RGC to electrical stimulation using the Euler algorithm as an iterative method.Two situations are considered in the simulation of cell bodies（Soma）:the absence of Ca²⁺related ion channels（HH model）and the presence of Ca²⁺related ion channels（FCM model）.Starting with three different stimulation modes,namely,direct current stimulation,step current stimulation,and sinusoidal current stimulation,the effects of different electrical stimuli on the release characteristics of action potentials are studied to analyze the role of Ca²⁺in the release process of action potentials.Firstly,the frequency of action potential emission and the single peak shape of the first action potential under direct current stimulation are discussed.The changes of threshold,peak,and spike time interval of action potential with the intensity of current stimulation are studied for the circular trajectory of the photographic plan.Then compare the effects of different current intensity transients in step current on the action potential release characteristics,and speculate on the effect of Ca²⁺on the action potential during the current step process.Finally,study the impact of the intensity and frequency of sinusoidal current and the accumulation of current on the action potential release characteristics.The results show that without Ca²⁺,the peak value of the action potential in the HH model is higher,and the delay time of the first action potential is slightly shorter,and Ca²⁺is related to the repolarization and post hyperpolarization of the action potential.Based on the FCM model,compare the difference of action potentials between the sodium channel band（SOCB）on the axon hillock and the cell body（Soma）.Similarly,first discuss the effects of direct current stimulation and step current stimulation on action potential.By comparing the firing frequency,spike time interval,delay time of the first action potential,and response to current step time,the response characteristics of the two locations to different current intensities are discussed.Secondly,study the effects of pulse width,pulse interval time,and pulse number of rectangular pulse electrical stimulation on the characteristics of action potential discharge,and combine their commonality with sinusoidal current stimulation to explore the role of current accumulation effect and relative refractory period in the process of action potential discharge,which can provide a reference for the selection of stimulation waveform of artificial retinal electrode arrays.Due to the different density of sodium ion channels in the two regions of RGC,they have different characteristics such as emission frequency,peak value,and delay time.This provides new ideas for optimizing the placement of electrode arrays and reducing energy consumption.