Shinmei Yasuhiro, Yamanobe Takanobu, Fukushima Junko, Fukushima Kikuro
Department of Ophthalmology, Hokkaido University, Japan.
J Neurophysiol. 2002 Apr;87(4):1836-49. doi: 10.1152/jn.00150.2001.
To track a slowly moving object during whole body rotation, smooth-pursuit and vestibularly induced eye movements must interact to maintain the accuracy of eye movements in space (i.e., gaze), and gaze movement signals must eventually be converted into eye movement signals in the orbit. To understand the role played by the cerebellar vermis in pursuit-vestibular interactions, in particular whether the output of the vermis codes gaze-velocity or eye-velocity, we examined simple-spike activity of 58 Purkinje (P-) cells in lobules VI-VII of head-stabilized Japanese monkeys that were trained to elicit smooth-pursuit eye movements and cancel their vestibuloocular reflex (VOR) during passive whole body rotation around horizontal, vertical, or oblique axes. All pursuit-sensitive vermal P-cells also responded during VOR cancellation, and the majority of them had peak modulation near peak stimulus velocity. The directions of maximum modulation during these two tasks were distributed in all directions with a downward preponderance. Using standard criteria, 40% of pursuit-sensitive vermal P-cells were classified as gaze-velocity. Other P-cells were classified either as eye/head-velocity group I (36%) that had similar preferred directions during pursuit and VOR cancellation but that had larger responses during VOR x1 when gaze remained stationary, or as eye/head-velocity group II (24%) that had oppositely directed or orthogonal eye and head movement sensitivity during pursuit and VOR cancellation. Eye/head-velocity group I P-cells contained cells whose activity was correlated with eye velocity. Modulation of many P-cells of the three groups during VOR x1 could be accounted for by the linear addition of their modulations during pursuit and VOR cancellation. When monkeys fixated a stationary target, over half of the P-cells tested, including gaze-velocity P-cells, discharged in proportion to the velocity of retinal motion of a second spot. These observations are in a striking contrast to our previous results for floccular vertical P-cells. Because we used identical tasks, these differences suggest that the two cerebellar regions are involved in very different kinds of processing of pursuit-vestibular interactions.
为了在全身旋转过程中追踪缓慢移动的物体，平滑追踪和前庭诱发的眼球运动必须相互作用，以维持眼球在空间中的运动准确性（即注视），并且注视运动信号最终必须转换为眼眶内的眼球运动信号。为了理解小脑蚓部在追踪-前庭相互作用中所起的作用，特别是蚓部的输出编码的是注视速度还是眼球速度，我们检测了58个浦肯野（P）细胞在头部稳定的日本猕猴小叶VI-VII中的简单锋电位活动，这些猕猴经过训练，在围绕水平、垂直或斜轴进行被动全身旋转时能够引发平滑追踪眼球运动并取消其前庭眼反射（VOR）。所有对追踪敏感的蚓部P细胞在VOR取消期间也有反应，并且它们中的大多数在刺激速度峰值附近具有峰值调制。这两项任务中最大调制方向在各个方向上分布，向下占优势。使用标准标准，40%对追踪敏感的蚓部P细胞被归类为注视速度型。其他P细胞要么被归类为眼/头速度I组（36%），其在追踪和VOR取消期间具有相似的偏好方向，但在注视保持静止时VOR×1期间反应更大，要么被归类为眼/头速度II组（24%），其在追踪和VOR取消期间眼球和头部运动敏感性方向相反或正交。眼/头速度I组P细胞包含其活动与眼球速度相关的细胞。三组中许多P细胞在VOR×1期间的调制可以通过它们在追踪和VOR取消期间调制的线性相加来解释。当猴子注视一个静止目标时，超过一半被测试的P细胞，包括注视速度型P细胞，按照第二个点的视网膜运动速度成比例放电。这些观察结果与我们之前对绒球垂直P细胞的结果形成了鲜明对比。因为我们使用了相同的任务，这些差异表明这两个小脑区域参与了非常不同类型的追踪-前庭相互作用处理。
