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目的:评估高速率电刺激对豚鼠听神经兴奋性的影响。方法:切开受试豚鼠圆窗膜,标准电极插入鼓阶大约4mm,两个靠近蜗尖的电极作为刺激电极,切开圆窗用压碎的颞肌封住。随机选择一耳为刺激耳,另一耳则为对照耳,均安装上标准电极,刺激电极在整个测试过程中保持不动。在保持刺激强度处在临床正常水平[电刺激诱发听觉脑干电位(EABR)阈值上6dB]情况下,用200(n=14)、400(n=10)、1000(n=11)、2000(n=10)脉冲数/s(PPS)四种不同的电刺激速率急性刺激45只听力正常豚鼠鼓阶内电极2h,记录急性刺激前、后3h内EABR的阈值和Ⅰ波幅值,比较急性刺激前、后EABR的Ⅰ波幅值的变化。结果:急性刺激电流强度固定在临床正常水平(EABR阈上6dB),急性刺激后EABR的Ⅰ波幅值同急性刺激前相比,采用200PPS刺激速率平均约升高20%;400PPS约升高9%;1000PPS约升高7%;2000PPS约升高30%。结论:在刺激电流强度为阈上6dB的情况下,人工耳蜗言语编码策略如果应用1000、2000PPS高速率电刺激不会导致听神经的兴奋性下降。此实验为临床上研制新的人工耳蜗采取高刺激速率语音信号处理方案提供了依据。
OBJECTIVE: To evaluate the effects of high-rate electrical stimulation on auditory nerve excitability in guinea pigs. Methods: The guinea pig round window membrane was incised. The standard electrode was inserted into the scala tympani about 4 mm. Two electrodes near the tip of the cochlea were used as the stimulation electrodes. The round window was closed with the crushed temporalis muscle. Randomly select one ear to stimulate the ear, the other ear is the control ear, are installed on the standard electrode, the stimulation electrode in the entire test process remain intact. (N = 14), 400 (n = 10), 1000 (n = 11), 2000 (n = 11) at a normal clinical level of stimulation intensity (6 dB above the EABR threshold for electrical stimulation) (n = 10) pulses / s (PPS) were used to acutely stimulate 45 electrodes of guinea pig’s guinea pigs for 2 hours. The threshold of EABR and the amplitude of Ⅰ wave were recorded before and 3h after acute stimulation Changes of Ⅰ wave amplitude of EABR before and after acute stimulation. Results: The intensity of acute stimulation was fixed at the normal level of clinic (6 dB above the EABR threshold). After acute stimulation, the amplitude of Ⅰ wave of EABR increased by about 20% on average with 200PPS stimulation rate compared with that before acute stimulation; %; 1000PPS about 7% higher; 2000PPS about 30% higher. CONCLUSION: Cochlear cochlear speech coding strategy using 1000 and 2000 PPS high-rate electrical stimulation does not lead to decreased excitability of the auditory nerve under stimulation current intensity of 6 dB above threshold. This experiment provides a basis for the clinical development of new cochlear implants to adopt a high stimulation rate speech signal processing scheme.