Angelaki Dora E, Zhou Hui-Hui, Wei Min
Department of Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Neurosci. 2003 Feb 15;23(4):1104-8. doi: 10.1523/JNEUROSCI.23-04-01104.2003.
Because we view the world from a constantly shifting platform when our head and body move in space, vestibular and visuomotor reflexes are critical to maintain visual acuity. In contrast to the phylogenetically old rotational vestibulo-ocular reflex (RVOR), it has been proposed that the translational vestibulo-ocular reflex (TVOR) represents a newly developed vestibular-driven mechanism that is important for foveal vision and stereopsis. To investigate the hypothesis that the function of the TVOR is indeed related to foveal (as opposed to full-field) image stabilization, we compared the three-dimensional ocular kinematics during lateral translation and rotational movements with those during pursuit of a small moving target in four rhesus monkeys. Specifically, we tested whether TVOR rotation axes tilt with eye position as in visually driven systems such as pursuit, or whether they stay relatively fixed in the head as in the RVOR. We found a significant dependence of three-dimensional eye velocity on eye position that was independent of viewing distance and viewing conditions (full-field, single target, or complete darkness). The slopes for this eye-position dependence averaged 0.7 +/- 0.07 for the TVOR, compared with 0.6 +/- 0.07 for visually guided pursuit eye movements and 0.18 +/- 0.09 for the RVOR. Because the torsional tilt versus vertical gaze slopes during translation were slightly higher than those during pursuit, three-dimensional eye movements during translation could partly reflect a compromise between the two different solutions for foveal gaze control, that of Listing's law and minimum velocity strategies. These results with respect to three-dimensional kinematics provide additional support for a functional difference in the two vestibular-driven mechanisms for visual stability during rotations and translations and establish clearly the functional goal of the TVOR as that for foveal visual acuity.
由于当我们的头部和身体在空间中移动时，我们是从一个不断变化的平台来观察世界的，所以前庭和视运动反射对于维持视力至关重要。与进化上古老的旋转前庭眼反射（RVOR）不同，有人提出平移前庭眼反射（TVOR）代表一种新发展的前庭驱动机制，对中央凹视觉和立体视觉很重要。为了研究TVOR的功能确实与中央凹（而非全视野）图像稳定相关这一假设，我们比较了四只恒河猴在横向平移和旋转运动期间以及追踪一个小的移动目标期间的三维眼运动学。具体而言，我们测试了TVOR旋转轴是否像在诸如追踪等视觉驱动系统中那样随眼位倾斜，或者它们是否像在RVOR中那样在头部中保持相对固定。我们发现三维眼速度对眼位有显著依赖性，且这种依赖性与观察距离和观察条件（全视野、单个目标或完全黑暗）无关。TVOR这种眼位依赖性的斜率平均为0.7±0.07，相比之下，视觉引导的追踪眼运动的斜率为0.6±0.07，RVOR的斜率为0.18±0.09。由于平移期间扭转倾斜与垂直注视斜率略高于追踪期间，所以平移期间的三维眼运动可能部分反映了中央凹注视控制的两种不同解决方案（即利斯廷定律和最小速度策略）之间的折衷。这些关于三维运动学的结果为旋转和平移期间视觉稳定的两种前庭驱动机制的功能差异提供了额外支持，并明确确立了TVOR的功能目标是中央凹视力。
