Waespe W, Schwarz U
Exp Brain Res. 1986;65(1):49-58. doi: 10.1007/BF00243829.
An eye velocity storage mechanism has been postulated in the vestibulo-optokinetic system to account for the prolongation of vestibular nystagmus (VN) and the occurrence of optokinetic after-nystagmus (OKAN). Presentation of a subject-stationary full-field surround during VN and OKAN (= full-field fixation) rapidly reduces activity related to eye velocity of the storage mechanism. If the subject-stationary full-field surround is presented for short periods during VN or OKAN, nystagmus resumes when the animal is again in darkness, but at a lesser velocity than would be predicted from a control response. This reduction in peak eye velocity after fixation reflects a decrease in activity of the storage mechanism due to full-field fixation. This decrease in activity occurs with a shorter time constant compared to that in control trials, it has been called "dumping". We demonstrate that a subject-stationary small target light presented during VN or OKAN (= target fixation) also reduces activity of the storage mechanism with a time constant slightly greater than that for full-field fixation, but still considerably smaller than that in control trials. In 3 monkeys the time constant of discharge was reduced during the post-rotatory period from 20 s in control trials to 4.6 s by fixation of a single target light and to 2.9 s by fixation of a full-field. The time constant of discharge was reduced during OKAN from 13.2 s in control trials to 3.8 s by target fixation and to 2.6 s by full-field fixation. We report a second experimental paradigm with which the dynamics of visual-vestibular interaction involving the eye velocity storage mechanism is analysed by means of transient step responses. In this paradigm eye velocity due to activation of the storage mechanism (OKAN) is forced to reverse by a short exposure to a full-field moving in the opposite direction of the slow phases of nystagmus. Short periods of eye velocity reversal did not reduce activity of the storage mechanism more rapidly than fixation, i.e. suppression of eye velocity alone. Fixation of a full-field or of a single target light during vestibular or optokinetic stimulation reduces peak nystagmus velocity after stimulation when monkeys are in darkness. Suppression of OKN by target fixation during full-field stimulation reduces the initial eye velocity of OKAN to 15-20% compared to the OKAN velocity when OKN is allowed to occur.(ABSTRACT TRUNCATED AT 400 WORDS)
在前庭视动系统中，已假定存在一种眼速度存储机制，以解释前庭眼震（VN）的延长和视动后眼震（OKAN）的发生。在VN和OKAN期间呈现静止的全视野背景（即全视野注视），会迅速降低与存储机制的眼速度相关的活动。如果在VN或OKAN期间短时间呈现静止的全视野背景，当动物再次处于黑暗中时，眼震会恢复，但速度低于根据对照反应预测的速度。注视后眼峰值速度的降低反映了由于全视野注视导致存储机制活动的减少。与对照试验相比，这种活动减少的时间常数更短，这被称为“倾倒”。我们证明，在VN或OKAN期间呈现静止的小目标光（即目标注视），也会降低存储机制的活动，其时间常数略大于全视野注视，但仍远小于对照试验中的时间常数。在3只猴子中，在旋转后阶段，通过固定单个目标光，放电时间常数从对照试验中的20秒减少到4.6秒，通过全视野固定减少到2.9秒。在OKAN期间，通过目标注视，放电时间常数从对照试验中的13.2秒减少到3.8秒，通过全视野固定减少到2.6秒。我们报告了第二种实验范式，通过瞬态阶跃响应分析涉及眼速度存储机制的视觉-前庭相互作用的动力学。在这种范式中，通过短暂暴露于与眼震慢相相反方向移动的全视野，使由于存储机制激活（OKAN）引起的眼速度被迫反转。短时间的眼速度反转不会比注视（即仅抑制眼速度）更快地降低存储机制的活动。在前庭或视动刺激期间固定全视野或单个目标光，会降低猴子在黑暗中刺激后的眼震峰值速度。在全视野刺激期间通过目标注视抑制视动性眼震（OKN），与允许OKN发生时的OKAN速度相比，会将OKAN的初始眼速度降低到15%-20%。
