【作者】 牛国毅；

【导师】 王晓远；

【作者基本信息】 天津大学 ， 电机与电器， 2007， 硕士

【摘要】 大脑是意识的主体,脑科学的研究一直吸引着众多研究者。大脑结构复杂,脑细胞之间除了宏观的电、磁等方面的联系外,还有分子的交换以及基本粒子的交换活动。对控制着人类思维、意识、学习和记忆等高级功能的大脑进行模拟仿真分析是目前研究大脑有效且无创的方法之一。脑电仿真是按一定的仿真算法模拟脑电产生、传播过程,然后根据某一时刻兴奋的神经组织所产生的动作电位和兴奋源的位置、大小和方向,用有限元法等数值算法求出兴奋的神经元在体表产生的电位。有了脑电仿真模型,通过设置模型参数可以仿真多种神经疾病。借助神经病理时体表电位的分布情况和脑电仿真模型,有助于研究神经异常形成的机理。本文从细胞静息电位和动作电位角度阐述生物组织的电特性,介绍神经元动作电位的产生、脑电产生的机理、脑电图的检测等;并从电磁学角度对大脑自身产生的电磁场进行数学描述,给出大脑电磁场问题的相关计算和脑电场有限元分析法的求解过程。用具有一定偶极矩的电流偶极子等效模型可以模拟大脑神经元电活动,本文采用不同偶极矩的单偶极子、偶极矩随时间变化的单偶极子、双偶极子作用于等效的四层同心球大脑模型产生的脑电场问题进行仿真,并对单偶极子作用于大脑等效模型产生的磁场进行仿真。分析仿真结果发现,用电流偶极子模型能较好地模拟神经元电活动产生的脑电场和脑磁场,仿真结果和脑电场的解析解吻合较好。由仿真结果可知,大脑表面距离神经元电活动源较近的区域产生的电位高,随着大脑兴奋源和观测点距离的增大,观测点的电位降低;不同强度的神经元电活动产生的脑电磁场强度是不同的。最后介绍根据头皮电位逆推大脑兴奋源位置和大小等信息的脑电逆问题求解方法。对脑电进行病理和认知等方面的分析可获得大脑神经活动源的信息,为临床上大脑病变的预防、诊断提供可靠地依据和参考。更多还原

【Abstract】 Brain is the sources of consciousness. Many scientific researchers are always attracted by the study of cerebrum. The configuration of brain is complex; cerebral cell connects with each other not only by macroscopically electricity and magnetism, but also by the change of molecular and elementary particle. Simulation is one of available and no-hurt ways to study brain which controls thought, consciousness, study, memory and so on. An aggregation of morphologically similar cells and associated intercellular matter acting together performs electrical activity. It is a way to simulate the production of electric potential between parts of brain in common use. Firstly, it needs simulate the processing of cause and spread of electric potential between parts of brain; then it needs to work out electric potential on the surface of head from the model which was used for further imitating its characteristics based on the electric activity originated by the excited nerve cell and the magnitude, orientation of nerve cell. Once we succeed in gaining the model of brain, we can imitate the process of much abnormal disease of the nervous system by setting the parameters of model. We can study the mechanism thoroughly, through which abnormity of brain comes into being on the basis of electric potential on the surface of scalp and model we previously design to study brain.This article tells of the electrical characteristic of biologic tissue from the angles of resting potential and action potential relating to cell. It also introduces the process of producing action potential, the mechanism and measurement of brain wave and also. It describes and calculates the electric field caused by brain on the principle of electromagnetism too. It gives the process of calculating brain’s electric field using finite-element analysis subsequently. Electric dipole with electric dipole moment can simulate the electric activity of neuron. Aimed at four spheres with one centre of a circle representing head, this article simulates the problem of brain’s electric field using the model of one current dipole with difference electric dipole moment and moment changes along with time based on finite-element analysis. The model of two current dipoles is also used in the article to compare with those results of one. Afterward, it simulates the magnetic field characterized by the existence of electric field of brain on the heap of single electric dipole. The article compares and analyzes the similarities and differences of those electrocardiograms gained through stimulation. Through the comparison of results, we found using the model of electric dipole can simulate electric field and magnetic produced by neuron. The results of simulation are accordance with the truth. The conclusion of simulation shows that potential of the area which closes up the dipole is high, while the potential of scalp is lower with the increase of the distance between the point of observation and the dipole. The electric activity of neuron with different intensity and orientation may come into being electromagnetic which is different from each other. At last, the article describes ways and means available to deduce the coordinate and intensity of neuron by the process of reverse-calculation according to the potential of scalp. We can obtain the information of neuron’s activity through the analysis on EEG to study of diseases of brain and its causes, processes, development, and consequences ,which provides the evidence and reference of brain’illness to help diagnoses and prevention.更多还原