新型螺旋电极胞外选择性刺激视神经的仿真分析

目的 电刺激中枢神经系统已用于治疗一些神经病、精神病和感觉障碍.尽管在一些应用里相当成功,但现有的刺激技术不能精确地控制激活靶向神经元.提出一种形状自适应的新型螺旋电极,实现选择性刺激视神经.方法 应用COMSOL Multiphysics建立视神经和新型螺旋电极的几何模型;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.引入激活函数来表征刺激效果,应用COMSOL仿真分析新型螺旋电极对视神经纤维选择性刺激的能力,并考虑电极触点位置的变化对选择性的影响.结果 假定激活函数的归一化阈值为0.1 V/m2,新型螺旋电极和传统袖套电极激活函数大于阈值的比例差异仅为1.2410％.当新型螺旋电极两端的电极触点靠近中间触点时,可以先激活细视神经纤维束,后激活粗纤维束.结论 仿真结果表明新型螺旋电极可以达到传统袖套电极的刺激效果.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.

Simulation analysis of extracellular selective stimulation of optic nerve with new helix electrode

Objective Electric stimulation of the central nervous system has been served as a treatment method for variety of neurological, psychiatric and sensory disorders. Despite considerable success in some applications, current stimulation techniques offer little control over which neuronal targets are activated by stimulation. This study aimed to present a new shape self-adaptive helix electrode for selective activation of optic nerve. Methods The geometric model of optic nerve and new helix electrode was elaborated with COMSOL Multiphysics. The new helix electrodes consist of silicone helix frame, which acted as support and insulation, and plat- inum contacts embedded within the frame. The activating function （AF） was introduced to characterize the stimulation effects, and the selectivity of activating optic nerve fascicle with new helix electrode was simulated by COMSOL Multiphysics, taking into account the variations of electrode contact locations. Results Assuming normalized AF threshold was 0.1 V/m2, the ratio difference of AF over threshold between new helix electrode and traditional electrode was only 1.241 0%. With contacts in two ends of helix electrode closer to the middle contact, the small nerve fascicle was first activated and then the large one. Conclusion The results show that the new helix electrodes have the same stimulation effects as that of traditional cuff electrodes. The new helix electrodes can selectively activate optic nerve fascicle with variations of electrode contact locations.