Departments of Otolaryngology/Head and Neck Surgery and Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA.
IEEE Trans Neural Syst Rehabil Eng. 2011 Feb;19(1):84-94. doi: 10.1109/TNSRE.2010.2065241. Epub 2010 Sep 2.
An implantable prosthesis that stimulates vestibular nerve branches to restore sensation of head rotation and vision-stabilizing reflexes could benefit individuals disabled by bilateral loss of vestibular (inner ear balance) function. We developed a prosthesis that partly restores normal function in animals by delivering pulse frequency modulated (PFM) biphasic current pulses via electrodes implanted in semicircular canals. Because the optimal stimulus encoding strategy is not yet known, we investigated effects of varying biphasic current pulse frequency, amplitude, duration, and interphase gap on vestibulo-ocular reflex (VOR) eye movements in chinchillas. Increasing pulse frequency increased response amplitude while maintaining a relatively constant axis of rotation. Increasing pulse amplitude (range 0- 325 μA) also increased response amplitude but spuriously shifted eye movement axis, probably due to current spread beyond the target nerve. Shorter pulse durations (range 28- 340 μs) required less charge to elicit a given response amplitude and caused less axis shift than longer durations. Varying interphase gap (range 25- 175 μs) had no significant effect. While specific values reported herein depend on microanatomy and electrode location in each case, we conclude that PFM with short duration biphasic pulses should form the foundation for further optimization of stimulus encoding strategies for vestibular prostheses intended to restore sensation of head rotation.
一种可植入的假体，通过刺激前庭神经分支来恢复头部旋转的感觉和稳定视觉的反射，可能使双侧前庭（内耳平衡）功能丧失的个体受益。我们开发了一种假体，通过在半规管中植入电极来输送脉冲频率调制（PFM）双相电流脉冲，从而在动物中部分恢复正常功能。由于尚不知道最佳的刺激编码策略，我们研究了改变双相电流脉冲频率、幅度、持续时间和相间间隙对南美栗鼠前庭眼动反射（VOR）眼球运动的影响。增加脉冲频率会增加响应幅度，同时保持相对恒定的旋转轴。增加脉冲幅度（范围 0-325μA）也会增加响应幅度，但会虚假地改变眼球运动轴，可能是由于电流在目标神经之外扩散。较短的脉冲持续时间（范围 28-340μs）需要较少的电荷量来产生给定的响应幅度，并且比较长的持续时间引起的轴偏移小。相间间隙的变化（范围 25-175μs）没有显著影响。虽然本文报告的具体值取决于每种情况下的微解剖结构和电极位置，但我们得出结论，具有短持续时间双相脉冲的 PFM 应该成为进一步优化用于恢复头部旋转感觉的前庭假体刺激编码策略的基础。
