Kramer P D, Shelhamer M, Zee D S
Department of Neurology, Johns Hopkins University, School of Medicine, Baltimore, MD 21287, USA.
Exp Brain Res. 1995;106(2):318-26. doi: 10.1007/BF00241127.
We investigated the effects of short-term vestibulo-ocular reflex (VOR) adaptation on the gain and phase of the VOR, and on eccentric gaze-holding in darkness, in five normal human subjects. For 1 h, subjects sat in a chair that rotated sinusoidally at 0.2 Hz while surrounded by a visual stimulus (optokinetic drum). The drum was rotated relative to the chair, to require a VOR with either a phase lead or lag of 45 deg (with respect to a compensatory phase of zero) with no change in gain, or a gain of 1.7 or 0.5 with no change in phase. Immediately before and after each training session, VOR gain and phase were measured in the dark with 0.2 Hz sinusoidal rotation. Gaze-holding was evaluated following 20 deg eccentric saccades in darkness. Adaptation paradigms that called only for a phase lead produced an adapted VOR with 33% of the required amount of phase change, a 20% decrease in VOR gain, and an increased centripetal drift after eccentric saccades made in darkness. Adaptation paradigms that called for a phase lag produced an adapted VOR with 29% of the required amount of phase change, no significant change in VOR gain, and a centrifugal drift after eccentric saccades. Adaptation paradigms requiring a gain of 1.7 produced a 15% increase in VOR gain with small increases in phase and in centripetal drift. Adaptation paradigms requiring a gain of 0.5 produced a 31% decrease in VOR gain with a 6 deg phase lag and a centrifugal drift. The changes in drift and phase were well correlated across all adaptation paradigms; the changes in phase and gain were not. We attribute the effects on phase and gaze-holding to changes in the time constant of the velocity-to-position ocular motor neural integrator. Phase leads and the corresponding centripetal drift are due to a leaky integrator, and phase lags and the corresponding centrifugal drift are due to an unstable integrator. These results imply that in the short-term adaptation paradigm used here, the control of drift and VOR phase are tightly coupled through the neural integrator, whereas VOR gain is controlled by another mechanism.
我们研究了短期前庭眼反射（VOR）适应对五名正常人类受试者VOR的增益和相位，以及对黑暗中偏心注视稳定的影响。受试者坐在一把椅子上，椅子以0.2Hz的频率做正弦旋转，持续1小时，同时周围有一个视觉刺激（视动鼓）。视动鼓相对于椅子旋转，要求VOR具有45度的相位超前或滞后（相对于补偿相位为零），增益不变，或者增益为1.7或0.5，相位不变。在每次训练前和训练后，在黑暗中以0.2Hz的正弦旋转测量VOR增益和相位。在黑暗中进行20度偏心扫视后评估注视稳定情况。仅要求相位超前的适应范式产生的适应VOR具有所需相位变化量的33%，VOR增益降低20%，并且在黑暗中进行偏心扫视后向心漂移增加。要求相位滞后的适应范式产生的适应VOR具有所需相位变化量的29%，VOR增益无显著变化，并且在偏心扫视后有离心漂移。要求增益为1.7的适应范式使VOR增益增加15%，相位和向心漂移略有增加。要求增益为0.5的适应范式使VOR增益降低31%，有6度的相位滞后和离心漂移。在所有适应范式中，漂移和相位的变化具有良好的相关性；相位和增益的变化则不然。我们将对相位和注视稳定的影响归因于速度到位置眼动神经积分器的时间常数变化。相位超前和相应的向心漂移是由于积分器泄漏，而相位滞后和相应的离心漂移是由于积分器不稳定。这些结果表明，在此处使用的短期适应范式中，漂移和VOR相位的控制通过神经积分器紧密耦合，而VOR增益则由另一种机制控制。
