Merfeld D M, Young L R
Man-Vehicle Laboratory, Massachusetts Institute of Technology, Cambridge 02139, USA.
Exp Brain Res. 1995;106(1):111-22. doi: 10.1007/BF00241361.
The vestibulo-ocular reflexes (VOR) are determined not only by angular acceleration, but also by the presence of gravity and linear acceleration. This phenomenon was studied by measuring three-dimensional nystagmic eye movements, with implanted search coils, in six male squirrel monkeys during eccentric rotation. Monkeys were rotated in the dark at a constant velocity of 200 degrees/s (centrally or 79 cm off axis) with the axis of rotation always aligned with gravity and the spinal axis of the upright monkeys. The monkey's orientation (facing-motion or back-to-motion) had a dramatic influence on the VOR. These experiments show that: (a) the axis of eye rotation always shifted toward alignment with gravito-inertial force; (b) the peak value of horizontal slow phase eye velocity was greater with the monkey facing-motion than with back-to-motion; and (c) the time constant of horizontal eye movement decay was smaller with the monkey facing-motion than with back-to-motion. All of these findings were statistically significant and consistent across monkeys. In another set of tests, the same monkeys were rapidly tilted about their naso-occipital (roll) axis. Tilted orientations of 45 degrees and 90 degrees were maintained for 1 min. Other than a compensatory angular VOR during the angular rotation, no consistent eye velocity response was observed during or following the tilt for any of the six monkeys. The absence of any eye movement response following tilt weighs against the possibility that translational linear VOR responses are due to simple high-pass filtering of the otolith signals. The VOR response during eccentric rotation was divided into the more familiar angular VOR and linear VOR components. The angular component is known to depend upon semicircular canal dynamics and central influences. The linear component of the response decays rapidly with a mean duration of only 6.6 s, while the axis of eye rotation rapidly aligns (< 10 s) with gravito-inertial force. These results are consistent with the hypothesis that the measurement of gravito-inertial force by the otolith organs is resolved into central estimates of linear acceleration and gravity, such that the central estimate of gravitational force minus the central estimate of linear acceleration approximately equals the otolith measurement of gravito-inertial force.
前庭眼反射（VOR）不仅由角加速度决定，还受重力和线性加速度的影响。通过植入搜索线圈测量六只雄性松鼠猴在偏心旋转过程中的三维眼球震颤眼动，对这一现象进行了研究。猴子在黑暗中以200度/秒的恒定速度旋转（中心旋转或离轴79厘米），旋转轴始终与重力以及直立猴子的脊柱轴对齐。猴子的朝向（面向运动方向或背向运动方向）对VOR有显著影响。这些实验表明：（a）眼球旋转轴总是朝着与重力惯性力对齐的方向移动；（b）猴子面向运动方向时水平慢相眼速度的峰值大于背向运动方向时；（c）猴子面向运动方向时水平眼动衰减的时间常数小于背向运动方向时。所有这些发现都具有统计学意义，并且在各只猴子之间是一致的。在另一组测试中，同样的猴子绕其鼻枕（翻滚）轴快速倾斜。保持45度和90度的倾斜方向1分钟。除了在角旋转期间有补偿性角VOR外，在倾斜过程中或倾斜后，六只猴子中没有一只观察到一致的眼速度反应。倾斜后没有任何眼动反应，这不利于平移线性VOR反应是由于耳石信号的简单高通滤波这一可能性。偏心旋转期间的VOR反应分为更为熟悉的角VOR和线性VOR成分。已知角成分取决于半规管动力学和中枢影响。反应的线性成分迅速衰减，平均持续时间仅为6.6秒，而眼球旋转轴迅速（<10秒）与重力惯性力对齐。这些结果与以下假设一致：耳石器官对重力惯性力的测量被分解为线性加速度和重力的中枢估计值，使得重力的中枢估计值减去线性加速度的中枢估计值大约等于耳石对重力惯性力的测量值。
