VISUAL‐VESTIBULAR INTERACTION IN VESTIBULAR NEURONS: FUNCTIONAL PATHWAY ORGANIZATION *
VISUAL‐VESTIBULAR INTERACTION IN VESTIBULAR NEURONS: FUNCTIONAL PATHWAY ORGANIZATION *
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前庭神经元中的视觉前庭相互作用：功能通路组织*
DOI：
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发表时间：
1981
影响因子：
5.2
通讯作者：
W. Precht
中科院分区：
文献类型：
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作者：
W. Precht
视觉周围大部分的运动的视觉信息可以通过交叉或交叉和非交叉的视网膜纤维到达大脑，并通过中央电路产生眼睛和/或头部运动，试图补偿周围运动，从而稳定视网膜上的给定视觉图像。这种速度控制系统的输入-输出关系已经在兔子、猫和猴子的水平视动眼球震颤（OKN）中得到了特别好的研究；'-5，但对从视网膜到眼运动神经元的通路组织知之甚少。因此，已经表明，在中心凹动物中，完全去除双侧视觉皮质后，OKN 仍然存在。 ～。 〜更具体地说，只有颞鼻周围运动引起的 OKN 几乎不受皮质消融的影响，而鼻颞定向刺激在没有视觉皮层的情况下会产生非常差的 OKN 反应。因此，没有视觉皮层的小凹动物表现出与完整的小凹动物（如兔子和大鼠）中发现的 OKN 模式类似。8 最近采用分裂视交叉范式或视束单侧部分的研究表明，最独立于视觉皮层的系统是对颞鼻周围运动做出反应的交叉视网膜系统。 ~ 所有其他系统（未交叉的颞鼻和鼻颞以及交叉的鼻颞）要么无法在没有皮层的情况下生成 OKN，要么只能介导非常差的反应。因此，由交叉视网膜离体系统介导的OKN是最基本的一种，只需要脑干的完整性，并且存在于迄今为止研究的所有脊椎动物中。因此，在研究 OKN 通路时，从这个系统发育上古老的系统开始是合理的。我们选择大鼠作为实验动物，因为在这种中心凹物种中，只有交叉颞鼻系统会通过单眼刺激产生显着的 OKN 反应。~为了进行比较，我们研究了猫的 OKN 通路，猫具有中央区域，可以被认为是中心凹物种的代表。基于对周围运动的速度阶跃产生的 OKN 的精确时间过程的研究，已经假设了直接和间接路径的存在。直接路径非常迅速地将 OKN 慢相速度带到最终稳态速度的一小部分，而间接路径则提供了 OKN 速度额外较慢的上升到在长时间刺激期间观察到的稳态值。从解剖学角度来说，直接路径可能由三神经元弧组成，该三神经元弧由视神经的轴突和中央中继神经元组成，其轴突直接接触眼运动神经元。这种连接的解剖学证据存在于鸟类和 rnph ib i~~ .~ , '~ 间接路径本质上是多突触的，并且涉及前庭核到运动神经元的路径。正是这条途径与本文的背景特别相关。
Visual information signaling motion of large parts of the visual surround may reach the brain via crossed or both crossed and uncrossed retinofugal fibers and generates through central circuits eye and/or head movements that try to compensate for surround motion, thereby stabilizing a given visual image on the retina. The input-output relationship of this velocity control system has been studied particularly well for the horizontal optokinetic eye nystagmus (OKN) in rabbit, cat, and monkey;'-5 but relatively little is known about the pathway organization from the retina to ocular motoneurons. Thus, it has been shown that in foveate animals, OKN is still present after complete removal of the bilateral visual c o r t e ~ . ~ . ~ More specifically, it is only the OKN evoked by temporonasal surround motion that is little affected hy cortical ablation, whereas nasotemporally directed stimuli produce a very poor OKN response in the absence of the visual cortex. Foveate animals without visual cortex, therefore, show an OKN pattern similar to that found in intact afoveate animals such as the rabbit and rat.'.8 Recent work employing the split optic chiasma paradigm or unilateral section of the optic tract has revealed that the system most independent of the visual cortex is the crossed retinofugal system responding to temporonasal surround m ~ t i o n . ~ All other systems (uncrossed temporonasal and nasotemporal and crossed nasotemporal) either are not able to generate OKN without the cortex or mediate only very poor responses. Therefore, the OKN mediated by the crossed retinofugal system is the most basic one, requires only the integrity of the brain stem, and is present in all vertebrates so far studied. In investigating OKN pathways, it is therefore reasonable to start out with this phylogenetically old system. We have chosen the rat as an experimental animal, since in this afoveate species, only the crossed temporonasal system generates significant OKN responses with monocular ~ t imula t ion .~ .~ For a comparison, we studied the OKN pathways in the cat, which has an area centralis and may be considered a representative of the foveate species. Based on studies of the exact time course of the OKN generated by velocity steps of surround motion, the existence of direct and indirect pathways has been p~s tu l a t ed .~ The direct path very rapidly brings the OKN slow-phase velocity to a fraction of the final steady-state velocity, and the indirect path provides the additional slower rise of OKN velocity to the steady-state value observed during prolonged stimulation. In anatomical terms, the direct path may consist of a three-neuron arc composed of the axons of the optic nerve and central relay neurons whose axons directly contact ocular motoneurons. Anatomical evidence for such connections exists in birds and a rnph ib i~~ .~ , '~ The indirect path is polysynaptic in nature and involves the vestibular nuclei on its way to motoneurons. It is this pathway that is of particular relevance in the context of the present paper.