Department of Otolaryngology-Head & Neck Surgery and Biomedical Engineering, Vestibular NeuroEngineering Laboratory, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Exp Brain Res. 2011 May;210(3-4):595-606. doi: 10.1007/s00221-011-2591-5. Epub 2011 Mar 4.
By sensing three-dimensional (3D) head rotation and electrically stimulating the three ampullary branches of a vestibular nerve to encode head angular velocity, a multichannel vestibular prosthesis (MVP) can restore vestibular sensation to individuals disabled by loss of vestibular hair cell function. However, current spread to afferent fibers innervating non-targeted canals and otolith end organs can distort the vestibular nerve activation pattern, causing misalignment between the perceived and actual axis of head rotation. We hypothesized that over time, central neural mechanisms can adapt to correct this misalignment. To test this, we rendered five chinchillas vestibular deficient via bilateral gentamicin treatment and unilaterally implanted them with a head-mounted MVP. Comparison of 3D angular vestibulo-ocular reflex (aVOR) responses during 2 Hz, 50°/s peak horizontal sinusoidal head rotations in darkness on the first, third, and seventh days of continual MVP use revealed that eye responses about the intended axis remained stable (at about 70% of the normal gain) while misalignment improved significantly by the end of 1 week of prosthetic stimulation. A comparable time course of improvement was also observed for head rotations about the other two semicircular canal axes and at every stimulus frequency examined (0.2-5 Hz). In addition, the extent of disconjugacy between the two eyes progressively improved during the same time window. These results indicate that the central nervous system rapidly adapts to multichannel prosthetic vestibular stimulation to markedly improve 3D aVOR alignment within the first week after activation. Similar adaptive improvements are likely to occur in other species, including humans.
通过感知三维（3D）头部旋转并电刺激前庭神经的三个壶腹分支以编码头部角速度，多通道前庭假体（MVP）可以为因前庭毛细胞功能丧失而丧失前庭感觉的个体恢复前庭感觉。然而，电流传播到非靶向管道和耳石末端器官的传入纤维会扭曲前庭神经激活模式，导致感知到的和实际头部旋转轴之间的不对准。我们假设，随着时间的推移，中枢神经机制可以适应以纠正这种不对准。为了验证这一点，我们通过双侧庆大霉素处理使五只南美栗鼠前庭功能丧失，并在它们的一侧植入了头戴式 MVP。在黑暗中以 2 Hz、50°/s 的峰值水平正弦头部旋转进行 3D 角前庭眼反射（aVOR）响应的比较，在持续 MVP 使用的第一天、第三天和第七天，在意图轴上的眼睛响应保持稳定（约为正常增益的 70%），而不对准在 1 周的假体刺激结束时显著改善。在检查的每个刺激频率（0.2-5 Hz）下，对其他两个半规管轴的头部旋转和对头部旋转也观察到类似的改善时间过程。此外，两只眼睛之间的不共轭程度在同一时间窗口内逐渐改善。这些结果表明，中枢神经系统迅速适应多通道假体前庭刺激，在激活后第一周内显著改善 3D aVOR 对准。在其他物种中，包括人类，可能会发生类似的适应性改善。
