A Study For The Properties Of Electraical Oscillation Activities Of Neuronal Network

Electrical synchronous oscillation activities are ubiquitous phenomenon in neural systems. The study about synchronization is the basis of understanding the form of the huge computational ability of the brain. It is helpful to explain the mechanism of neural diseases and to assist to diagnose brain diseases by electroencephalogram, and it is What are the origin and the mechanism of synchronization and what is its effect, which have excited the huge attention of many researchers and are the focus for study.Noises are ubiquitous in vivo and can alter the response of neurons and the signal propagation in various ways. However, how does noise affect the origination of neural signal and how do noise and synapse alter the propagation of the signal jointly? These issues have stimulated interest of many biologists,bioelectromagnetics scientists and physicists..By inspiring of the above-mentioned sense, our work has studied in detail the effects of noise on the action potential of a single neuron, the noise intensity and the coupled strength on frequency locking, the noise intensity and the coupling strength on the synchronization, the spike timing precision and the signal propagation between the two neuronal ensembles. By rigorous numerical simulation, the work makes a valuable exploration in the propagation of neural signal. The major original results in the thesis are summarized as follows:1. For a single neuron, the spike rate increases with the noise intensity, which is the basis of the noise-induced frequency locking between neurons.2. Rate synchronization of two coupled neurons is studied. The noise intensity and the coupled strength play a complementary role on neuronal synchronous activity: A three-dimensional diagram is plotted to show the synchronization regime.3. Adopting the dynamical mean-field approximation theory and population code, it is discussed by numerical simulation that the effects of noise intensity and the coupling strength on the synchronization and the spike timing precision, and some new results are gotten: (1) Noise increases the randomness of the neuron response and decreases the correlation and the synchronization, and the distribution of the membrane voltage broadens, the spike timing precision decreases; (2) Coupling among neurons works to improve the synchronous dynamics and to suppress local fluctuations, and the distribution of the membrane voltage become narrower, the spike timing precision increases; (3) Compared with the chemical synapse, the electrical synapse can enhance the synchronization and the spike timing precision largely for the same coupling, which is significative.4. The FitzHugh-Nagumo neuron ensembles are constructed, and they are calculated that the thresholds of the noise intensity and the coupling strength affecting the signal propagation.