Suppression of the human vestibulo-ocular reflex by visual fixation or forced convergence in the dark, with a model interpretation
Suppression of the human vestibulo-ocular reflex by visual fixation or forced convergence in the dark, with a model interpretation
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DOI：
10.1076/ceyr.26.4.281.15426
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发表时间：
2003-05-01
影响因子：
2
通讯作者：
Harper, HW
中科院分区：
文献类型：
--
作者：
Gizzi, MS;Harper, HW
六名正常人在黑暗中经历了120度/秒的偏航轴速度步进。在旋转后的时间里，受试者要么做一个空任务（什么都不做）；眼球运动任务（强迫收敛：交叉眼睛）；或者是一项视觉任务（将头部固定的目标固定在10度光/暗条的背景下）。任务在旋转后3秒开始，并持续2、5、10或15秒。眼运动和视觉任务在不同的日子进行测试。记录每个受试者在每个任务持续时间内重复五次。观察到平均VOR增益为0.52，不随实验条件变化。会聚和注视均能明显抑制眼球震颤；事实上，两种不同任务获得的VORs在表面上是相似的。然而，汇聚日的平均零任务时间常数为9.4 s，注视日的平均零任务时间常数为8.4 s，注视日的总体零任务VOR幅度虽小但显著降低。同时，收敛后的慢相速度略有增强，而固定后的速度显著降低。速度存储的时间常数在收敛响应为10.1 s，在固定响应为8.2 s。这些差异可以通过视注视期间中央速度存储的改变来理解，而这种改变在趋同时不会发生。在为猴子数据建立的VOR模型的背景下分析平均固定数据。通过适当的参数选择，该模型可以准确地再现人类数据的大部分特征。得到了人体锥体时间常数3.3 s的估计值。与猴子相比，固定抑制更大，固定后速度降低更小。视网膜滑动本身就很好地解释了这一点；积分器分流的“速度倾销”如果存在的话，必须是轻微的。该模型正确地表示了所有固定时间内的固定后VOR。
Six normal humans experienced yaw axis steps of velocity at 120degrees/s in the dark. During the post-rotary period, subjects either had a null-task (do nothing); an ocular motor task (forced convergence: crossing the eyes); or a visual task (fixating a head-stationary target against a background of 10degrees light/dark bars). Tasks started at 3 s post-rotation, and lasted either 2, 5, 10, or 15 s. Ocular motor and visual tasks were tested on different days. Five repetitions of each task duration were recorded for each subject. A mean VOR gain of 0.52 was observed, which did not vary with experimental conditions. Both convergence and fixation markedly suppressed nystagmus; in fact, the VORs obtained with the two different tasks are superficially similar in appearance. However, mean null-task time-constants were 9.4 s for convergence days, but 8.4 s for fixation days, and there was a small but significant reduction in overall null-task VOR amplitude on fixation days. Also, post-convergence slow-pase velocities were slightly enhanced, while post-fixation velocities were significantly reduced. The time-constant of velocity storage was found to be 10.1 s for convergence responses and 8.2 s for fixation responses. These differences can be understood in terms of modifications in central velocity storage during visual fixation which do not occur with convergence. The mean fixation data were analyzed in the context of a VOR model well-established for monkey data. With appropriate choice of parameters, this model accurately reproduces most features of the human data. An estimate for the human cupula time-constant of 3.3 s is obtained. Compared with the monkey, fixation suppression is greater and post-fixation velocity reduction less. Retinal slip alone accounts well for this; "velocity dumping" by an integrator shunt must be slight if present at all. The model correctly represents the post-fixation VOR for all durations of fixation.