Tchelidze Tamara, Hess Bernhard J M
Department of Neurology, University Hospital Zurich, Zurich, Switzerland.
J Neurophysiol. 2008 Jan;99(1):96-111. doi: 10.1152/jn.00804.2007. Epub 2007 Nov 7.
To investigate the role of noncommutative computations in the oculomotor system, three-dimensional (3D) eye movements were measured in seven healthy subjects using a memory-contingent vestibulooculomotor paradigm. Subjects had to fixate a luminous point target that appeared briefly at an eccentricity of 20 degrees in one of four diagonal directions in otherwise complete darkness. After a fixation period of approximately 1 s, the subject was moved through a sequence of two rotations about mutually orthogonal axes in one of two orders (30 degrees yaw followed by 30 degrees pitch and vice versa in upright and 30 degrees yaw followed by 20 degrees roll and vice versa in both upright and supine orientations). We found that the change in ocular torsion induced by consecutive rotations about the yaw and the pitch axis depended on the order of rotations as predicted by 3D rotation kinematics. Similarly, after rotations about the yaw and roll axis, torsion depended on the order of rotations but now due to the change in final head orientation relative to gravity. Quantitative analyses of these ocular responses revealed that the rotational vestibuloocular reflexes (VORs) in far vision closely matched the predictions of 3D rotation kinematics. We conclude that the brain uses an optimal VOR strategy with the restriction of a reduced torsional position gain. This restriction implies a limited oculomotor range in torsion and systematic tilts of the angular eye velocity as a function of gaze direction.
为了研究非对易计算在动眼系统中的作用，我们使用记忆依赖的前庭眼动范式，对7名健康受试者的三维（3D）眼动进行了测量。受试者必须注视一个发光点目标，该目标在完全黑暗的环境中，于四个对角线方向之一、20度的偏心位置短暂出现。在大约1秒的注视期后，受试者以两种顺序之一，绕相互正交的轴进行两次旋转（在直立状态下，先进行30度偏航，然后进行30度俯仰，反之亦然；在直立和仰卧状态下，先进行30度偏航，然后进行20度横滚，反之亦然）。我们发现，绕偏航轴和俯仰轴连续旋转引起的眼扭转变化，取决于旋转顺序，这与3D旋转运动学的预测一致。同样，在绕偏航轴和横滚轴旋转后，扭转也取决于旋转顺序，但这是由于最终头部相对于重力的方向变化所致。对这些眼动反应的定量分析表明，远视力中的旋转前庭眼反射（VOR）与3D旋转运动学的预测紧密匹配。我们得出结论，大脑使用了一种最优的VOR策略，但存在扭转位置增益降低的限制。这种限制意味着扭转时动眼范围有限，且角眼速度会根据注视方向系统地倾斜。
