Development of auditory brainstem implant

本课题旨在为有神经损伤的患者建立听觉假体的设计方法。我们特别关注听觉系统，并取得了以下主要成果：(1)开发了脑干植入系统的动物模型，该系统包括用于大脑皮层记录的表面微电极和用于耳蜗核脑干刺激的尖峰微电极阵列；(2)基于听觉皮层功能组织的脑干刺激对音高和强度感觉的验证；(3)“多重门控刺激”的发展，它可以选择性地激活电极之间的神经。表面微电极阵列外皮层测量高分辨率听觉皮层信号。该阵列采用聚酰亚胺衬底，以符合弯曲和脉动的皮质表面。该阵列在一个2毫米见方的区域内有70个记录点。尖峰微电极阵列以400-□m的间距排列成网格形式。我们首先研究纯音诱发的听觉皮层反应和基于这些反应的听觉皮层组织。根据刺激的频率和强度，反应表现出特征的时空模式。脉冲微电极阵列刺激脑干耳蜗核，其诱发反应与声诱发反应具有较好的一致性。此外，我们的结果强烈表明，当脑干的适当位置在适当的电流强度下受到刺激时，音高和强度感觉是可能的。我们通过神经方程模拟和大鼠脊髓刺激的体内实验，论证了门控刺激的可行性。该技术广泛地使用“阴极源电极”产生动作电位，同时使用“阳极栅电极”阻止不必要的传播，从而导致电极之间的选择性传播。少

This project purposes to establish design methodology for auditory prostheses for patients having some neural impairment. We especially focused on auditory systems and accomplished following major achievements : (1) Development of an animal model for a brainstem implant system, which includes the surface microelectrode for anditory cortical recording and a spike microelectrode array for cochlear nuclear brainstem stimulation ; (2) Validation of brainstem stimulation for pitch and intensity sensation, based on investigation of auditory cortical functional organization ; and (3) Development of "the multiple gating stimulation," which can selectively activate nerves placing in between electrodes.The surface microelectrode array epi-cortically measures high-resolution auditory cortical signals. The array employs a polyimide substrate so as to conform curved and pulsating cortical surface. The array has 70 recording points in a 2-mm-square area. The spike microelectrode array files 16 tungs … More ten microelectrodes in a grid form with 400-□m spacing.We first investigate pure-tone-evoked auditoly cortical responses and auditory cortical organizations based on the responses. The responses represent characteristic spatio-temporal patterns depending on frequency and intensity of the stimuli. The spike microelectrode array, then, stimulates the brainstem cochlear nucleus, and the evoked responses have good agreement with acoustically evoked responses. Moreover, our results strongly suggest pitch and intensity sensation is possible when an adequate position at a brainstem is stimulated at an adequate current intensity.We demonstrate the feasibility of the gating stimulation via simulations with nerve equations and in vivo experiments of rat spinal cord stimulation. The technique broadly generates action potentials with "the cathodic source electrodes," and simultaneously blocks unnecessary propagation with "the anodic gate electrodes," resulting in selective propagation in between electrodes. Less