Waespe W, Schwarz U, Wolfensberger M
Department of Neurology, University of Zürich, Switzerland.
Exp Brain Res. 1992;89(2):311-22. doi: 10.1007/BF00228247.
After destruction of the peripheral vestibular system which is not activated by moving large-field visual stimulation, not only labyrinthine-ocular reflexes but also optokinetic-ocular responses related to the "velocity storage" mechanism are abolished. In the normal monkey optokinetic-ocular responses are reflected in sustained activity changes of central vestibular neurons within the vestibular nuclei. To account for the loss of optokinetic responses after labyrinthectomy, inactivation of central vestibular neurons consequent on the loss of primary vestibular activity is assumed to be of major importance. To test this hypothesis we recorded the neural activity within the vestibular nuclear complex in two chronically prepared Rhesus monkeys during a period from one up to 9 and 12 months after both vestibular nerves had been cut. The discharge characteristics of 829 cells were studied in relation to eye fixation, and to a moving small and large (optokinetic) visual stimulus producing smooth pursuit (SP) eye movements and optokinetic nystagmus (OKN). Units were grouped into different subclasses. After chronic bilateral vestibular neurectomy (BVN) we have found: (1) a rich variety of spontaneously active cells within the vestibular nuclear complex, which--as far as comparison before and after BVN is possible--belong to all subclasses of neurons functionally defined in normal monkey; and (2) no sustained activity changes which are related to the activation of the "velocity storage" mechanism; this is especially true for "pure-vestibular", "vestibular-pause" and "tonic-vestibular-pause" cells in normal monkey which show a "pure", "pause" and "tonic-pause" firing pattern after BVN. Neurons which are modulated by eye position are, however, modulated with the velocity of slow eye movements with comparable sensitivity during SP and OKN. Retinal slip is extremely rarely encoded. The results of the present study do not directly answer the question why the "velocity storage" mechanism is abolished after BVN but they suggest that only a small number of central vestibular cells may be inactivated by neurectomy.
在未被大视野视觉刺激激活的外周前庭系统被破坏后，不仅迷路性眼反射，而且与“速度存储”机制相关的视动性眼反应都被消除。在正常猴子中，视动性眼反应反映在前庭核内中央前庭神经元的持续活动变化中。为了解释迷路切除术后视动反应的丧失，假定由于初级前庭活动丧失导致的中央前庭神经元失活具有重要意义。为了验证这一假设，我们在两只慢性制备的恒河猴双侧前庭神经切断后的1至9个月和12个月期间，记录了前庭核复合体中的神经活动。研究了829个细胞的放电特性与眼注视以及产生平稳跟踪（SP）眼运动和视动性眼球震颤（OKN）的移动小和大（视动性）视觉刺激的关系。将单位分为不同的亚类。在慢性双侧前庭神经切断术（BVN）后，我们发现：（1）前庭核复合体内有丰富多样的自发活动细胞，就BVN前后的比较而言，这些细胞属于正常猴子中功能定义的所有神经元亚类；（2）没有与“速度存储”机制激活相关的持续活动变化；对于正常猴子中的“纯前庭”、“前庭暂停”和“紧张性前庭暂停”细胞尤其如此，它们在BVN后表现出“纯”、“暂停”和“紧张性暂停”的放电模式。然而，受眼位调制的神经元在SP和OKN期间以与慢眼运动速度相当的敏感性进行调制。视网膜滑动极少被编码。本研究结果并未直接回答为什么BVN后“速度存储”机制被消除的问题，但它们表明只有少数中央前庭细胞可能因神经切断术而失活。
