袖套微电极胞外电刺激视神经的建模与仿真

项目名称： 袖套微电极胞外电刺激视神经的建模与仿真

项目编号： No.30870649

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 原子能技术

项目作者： 乔清理

作者单位： 天津医科大学

项目金额： 29万元

中文摘要： 视觉假体是重建部分盲人视觉的康复装置。视神经刺激是视觉假体实现的一种方法。本项目建立一个由刺激电极，组织容积导体和视神经组成的胞外电刺激视神经模型。应用COMSOL建立圆柱形视神经模型和新型螺旋电极模型。视神经模型考虑了脑脊液（CSF）厚度变化；新型电极由起支撑和绝缘隔离作用的硅橡胶螺旋支架和嵌入支架内的铂金触点组成。应用COMSOL计算电极的三维电场。引入激活函数来表征刺激效果和分析新型螺旋电极对视神经纤维选择性刺激的能力。分别利用Matlab和Labview对视网膜神经节FCM细胞模型和其它两个视神经模型, 进行数值计算与计算机仿真, 比较其在不同电流刺激下的响应, 并用相平面分析方法来分析其动力学特征。结果表明，改变新型螺旋电极的触点位置可以实现选择性激活视神经纤维束。在相同的刺激条件下，纵向三电极结构比双电极结构（电极分别位于神经干对侧）的电流密度值要大。脑脊液层对电流的散射阻碍使神经刺激效果变差。FCM的5种离子通道在一个动作电位形成过程中, 作用时间不同, 对动作电位形成的影响不同。本项目可为电极和刺激器优化设计，刺激效果预测和假体应用提供理论基础。

中文关键词： 视神经；螺旋袖套电极；有限元方法；胞外电刺激；FCM模型

英文摘要： Visual prosthesis is a rehabilitation device to restore vision to part of the blind subjects. Stimulating optic nerve is one method of proposed visual prostheses. A model of extracellular electrical stimulation of optic nerve was presented in this project, including stimulation electrode, tissue volume conductor and optic nerve. A cylindrical model of optic nerve，taking into account possible variations of the thickness of cerebrospinal fluid (CSF), and new helix electrode were constructed with COMSOL，a finite element package. The new helix electrodes consist of silicone helix frame, acting as support and insulation, and platinum contacts embedded within the frame. The spatial distribution of 3D electric field generated by optic nerve electrical stimulation with Helical cuff electrode was analyzed with COMSOL. The activating function was introduced to characterize the stimulation effect and the selectivity of activating optic nerve fascicle with new helical electrode. The FCM model, a kind of retinal ganglion cell model, and other two optic nerve filer models were calculated and simulated with Matlab and Labviews,respectively. The responses were compared under different electrical stimulations, and model dynamic characteristics were analyzed with phase plane method. It was shown that our new helix electrodes can selectively activate optic nerve fascicle by changing electrode contact locations; and under the same stimulation conditions, the longitudinal tripolar electrode structure could generate larger current density than that of biopolar electrode structure (located in the opposite of nerve trunk),and the diffuse current distribution generated by CSF makes nerve stimulation less effective ,and Five ion channels in retinal ganglion cells played different roles as they acted at different time during the formation of a single action potential. The work in this project can provide theoretical foundation for optimization of the electrode and electrical stimulator design and, prediction of stimulating effectiveness, and the prosthesis application.

英文关键词： Optic nerve;Helical cuff electrode;Finite elements method;Extracellular electric stimulation;FCM model