【作者】 张素花；

【导师】 展永；

【作者基本信息】 河北工业大学 ， 电工理论与新技术， 2006， 博士

【摘要】 同步电振荡活动是神经系统中普遍存在的一种现象,对同步电振荡活动的研究,是理解大脑非凡计算能力形成的基础,也有助于解释神经疾病的发病机理,辅助脑电科学诊断疾病,同步电振荡活动产生的起源和机制是什么?其作用是什么?这些问题已引起人们极大关注,成为神经科学领域研究的热点。基于统计理论的广义噪声在生物体内部普遍存在,它从不同的方面影响神经元的动力学活动以及神经电信号的传递。噪声如何影响神经信号的发生?噪声和突触如何协同工作来影响神经信号的转导、传递?这些问题引起了神经科学工作者、生物电磁学工作者以及物理学工作者的极大兴趣。在上述双重意义的鼓舞下,本工作系统分析了噪声对单个神经元触发动作电位的影响、噪声和耦合对两个神经元频率同步活动的影响、噪声和电突触耦合如何协同影响有限多个神经元组成的神经网络的精确同步活动和触发动作电位时间精确性、以及它们对神经元群体之间信号传递的影响。对神经网络内电振荡活动特性的研究做了有益的探索。本文的主要成果是:1、对于单个神经元而言,随着噪声强度的增加,其触发动作电位的频率也随之增加,这恰恰为噪声可以诱发神经元同步振荡活动的基础;2、按照频率编码的思想,精确分析了噪声和耦合对两个神经元同步活动的影响:噪声强度和耦合强度对神经元的同步活动起着相互补充的作用,绘制了同步活动和噪声强度、耦合强度的三维关系图;3、采用动力学平均场近似理论和群体编码的思想,对个FitzHugh-Nagumo神经元网络的精确同步活动和触发动作电位时间精确性进行分析,其结果为:(1)噪声增加神经元活动的随机性,减小神经元活动的关联性,降低系统的同步活动,膜电位的分布展宽,触发动作电位时间精确性降低;(2)耦合强度可以提高神经元的同步活动,抑制系统内部局域的波动,膜电位分布变窄,触发动作电位时间精确性提高;(3)非常值的重视的是与化学突触相比较,在相同的耦合强度下,电突触能够极大地提高神经元的同步振荡活动和触发动作电位时间精确性。N4、建立了FitzHugh-Nagumo神经元群体模型,计算了影响两个群体之间信号传递的噪声强度和耦合强度的阈值。更多还原

【Abstract】 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.更多还原