Demer J L, Crane B T
Jules Stein Eye Institute, Department of Ophthalmology, University of California, Los Angeles 90095-7002, USA.
Otolaryngol Head Neck Surg. 1998 Jul;119(1):78-88. doi: 10.1016/S0194-5998(98)70176-7.
This article summarizes six recent degree-of-freedom studies of visual-vestibular interaction during natural activities and relates the findings to canal-otolith interactions evaluated during eccentric axis rotations. Magnetic search coils were used to measure angular eye and head movements of young and elderly subjects. A flux gate magnetometer was used to measure three-dimensional head translation. Three activities were studied: standing quietly, walking in place, and running in place. Each activity was evaluated with three viewing conditions: a visible target viewed normally, a remembered target in darkness, and a visible target viewed with x2 binocular telescopic spectacles. Canal-otolith interaction was assessed with passive, whole-body, transient, and steady-state rotations in pitch and yaw at multiple frequencies about axes that were either oculocentric or eccentric to the eyes. For each rotational axis, subjects regarded visible and remembered targets located at various distances. Horizontal and vertical angular vestibulo-ocular reflexes were demonstrable in all subjects during standing, walking, and running. When only angular gains were considered, gains in both darkness and during normal vision were less than 1.0 and were generally lower in elderly than in young subjects. Magnified vision with x2 telescopic spectacles produced only small gain increases as compared with normal vision. During walking and running all subjects exhibited significant mediolateral and dorsoventral head translations that were antiphase locked to yaw and pitch head movements, respectively. These head translations and rotations have mutually compensating effects on gaze in a target plane for typical viewing distances and allow angular vestibulo-ocular reflex gains of less than 1.0 to be optimal for gaze stabilization during natural activities. During passive, whole-body eccentric pitch and yaw head rotations, vestibulo-ocular reflex gain was modulated as appropriate to stabilize gaze on targets at the distances used. This modulation was evident within the first 80 msec of onset of head movement, too early to be caused by immediate visual tracking. Modeling suggests a linear interaction between canal signals and otolith signals scaled by the inverse of target distance. Vestibulo-ocular reflex performance appears to be adapted to stabilize gaze during translational and rotational perturbations that occur during natural activities, as is appropriate for relevant target distances. Although immediate visual tracking contributes little to gaze stabilization during natural activities, visual requirements determine the performance of vestibulo-ocular reflexes arising from both canals and otoliths.
本文总结了近期六项关于自然活动中视觉 - 前庭相互作用的自由度研究，并将研究结果与在偏心轴旋转过程中评估的半规管 - 耳石相互作用相关联。使用磁搜索线圈测量年轻和老年受试者的眼球和头部角运动。使用磁通门磁力计测量三维头部平移。研究了三项活动：安静站立、原地行走和原地跑步。每项活动在三种视觉条件下进行评估：正常观看可见目标、在黑暗中回忆目标以及使用2倍双目望远镜眼镜观看可见目标。通过在俯仰和偏航方向上围绕以眼为中心或偏离眼睛的轴进行多个频率的被动、全身、瞬态和稳态旋转来评估半规管 - 耳石相互作用。对于每个旋转轴，受试者注视位于不同距离的可见和回忆目标。在站立、行走和跑步过程中，所有受试者的水平和垂直角前庭眼反射均明显可见。仅考虑角增益时，黑暗中和正常视觉时的增益均小于1.0，且老年人的增益通常低于年轻人。与正常视觉相比，使用2倍望远镜眼镜放大视觉仅使增益略有增加。在行走和跑步过程中，所有受试者均表现出明显的内外侧和背腹侧头部平移，分别与偏航和俯仰头部运动反相锁定。对于典型观看距离，这些头部平移和旋转对目标平面内的注视具有相互补偿作用，并使小于1.0的角前庭眼反射增益在自然活动中对注视稳定最为理想。在被动的全身偏心俯仰和偏航头部旋转过程中，前庭眼反射增益会进行适当调制，以将注视稳定在所用距离的目标上。这种调制在头部运动开始后的前80毫秒内就很明显，太早以至于不可能由即时视觉跟踪引起。模型表明，半规管信号和耳石信号之间存在线性相互作用，其比例与目标距离的倒数成比例。前庭眼反射性能似乎经过调整，以在自然活动中发生的平移和旋转扰动期间稳定注视，这对于相关目标距离是合适的。尽管即时视觉跟踪在自然活动中对注视稳定的贡献很小，但视觉需求决定了来自半规管和耳石的前庭眼反射的性能。
