Wearne S, Raphan T, Cohen B
Department of Neurology, Mount Sinai School of Medicine, New York, NY 10029, USA.
J Neurophysiol. 1997 Aug;78(2):1193-7. doi: 10.1152/jn.1997.78.2.1193.
During nystagmus induced by the angular vestibuloocular reflex (aVOR), the axis of eye velocity tends to align with the direction of gravito-inertial acceleration (GIA), a process we term "spatial orientation of the aVOR." We studied spatial orientation of the aVOR in rhesus and cynomolgus monkeys before and after midline section of the rostral medulla abolished all oculomotor functions related to velocity storage, leaving the direct optokinetic and vestibular pathways intact. Optokinetic afternystagmus and the bias component of off-vertical-axis rotation were lost, and the aVOR time constant was reduced to a value commensurate with the time constants of primary semicircular canal afferents. Spatial orientation of the aVOR, induced either during optokinetic or vestibular stimulation, was also lost. Vertical and roll aVOR time constants could no longer be lengthened in side-down or supine/prone positions, and static and dynamic tilts of the GIA no longer produced cross-coupling from the yaw to pitch and yaw to roll axes. Consequently, the induced nystagmus remained entirely in head coordinates after the lesion, regardless of the direction of the resultant GIA vector. Gains of the aVOR and of optokinetic nystagmus to steps of velocity were unaffected or slightly increased. These results are consistent with a model in which the direct aVOR pathways are organized in semicircular canal coordinates and spatial orientation is restricted to the indirect (velocity storage) pathways.
在由角前庭眼反射（aVOR）诱发的眼球震颤期间，眼速度轴倾向于与重力惯性加速度（GIA）方向对齐，我们将这一过程称为“aVOR的空间定向”。我们研究了在延髓前部中线横断消除了所有与速度存储相关的眼球运动功能之前和之后，恒河猴和食蟹猴中aVOR的空间定向情况，而直接视动和前庭通路保持完整。视动性眼震后效和离垂直轴旋转的偏差成分消失，并且aVOR时间常数降低到与初级半规管传入纤维的时间常数相当的值。在视动或前庭刺激期间诱发的aVOR的空间定向也消失了。在侧卧或仰卧/俯卧位时，垂直和横滚aVOR时间常数不再能够延长，并且GIA的静态和动态倾斜不再产生从偏航到俯仰以及从偏航到横滚轴的交叉耦合。因此，损伤后诱发的眼球震颤完全保持在头部坐标系中，而与合成GIA矢量的方向无关。aVOR和视动性眼震对速度阶跃的增益未受影响或略有增加。这些结果与一个模型一致，在该模型中，直接aVOR通路按半规管坐标系组织，并且空间定向仅限于间接（速度存储）通路。
