Neuronal Discharge Model Revisiting And Integration Of Frequency In Auditory System

Electrical activity of the nervous system is a process of production and transmission of neural action potential pulse. Neural coding is reflected by the time rhythmic of neural action potential pulse. Currently, the neuron model based on the MP model only simulate the output process of neuron, however, it gives no explanations to when action potentials are generated. The purpose of this research is to study how the action potentials are generated in neuron to code input signal in the form of time series by the establishment of mathematical model of neuron, and apply this model to the information exchange in primary central nervous system.This study reviews the neurobiology and physiology of hearing, and the models of neuron discharge were classified to better evaluate their advantages and disadvantages.In the following chapters, combined with the characteristic of time delay effect of basilar membrane of cochlea, a novel neuron discharge model is proposed and simulated in single channel as well as 8 channels respectively on the platform of Matlab7.0.1. The distribution densities of a series of action potentials which are obtained in our experiments are in accordance with the physiological data. These simulation results approve that information input of nerve cells is realized by time-coded action potential.Finally, vibration mode of cochlea and the traveling wave theory are introduced, and computer simulations are performed to justify the characteristic of integration of frequency in auditory system:1.The time delay in the integration of frequency in auditory system can eliminate noise in original signal and amplify original signal; The order of filter affects delay time, and the delay time is lengthened with the increase of filter order. Different input signal frequency, filter sampling rate and center frequency have no effect in the change of delay time. These facts indicate that the time delay effect in the integration of frequency in auditory system is unrelated to the inherent feature of the filter but a specific effect in the process of integration of frequency.2. The position of maximum amplitude in filtered signal is related to the frequency of input signal and the central frequency of channels, which validate that, in cochlear, the position of maximum displacement in response to sinusoids of different frequency; 3. Central frequency can be altered when the weights of different channels are changed, which makes the information transferred by nerve cells is diversified.This study provides new perspective and ideas for the study of mechanism of nerve center based on mathematical model and the research and application of fuzzy theory.