CEREBELLAR MODULES AND EYE MOVEMENT CONTROL

长期目标是通过以下方式更好地了解小脑功能 研究眼球运动背后的神经元信号处理 由自然刺激引起的。这些实验将集中在 兔的小叶。本课程的中心主题是 小叶需要在内在参照内部和之间进行映射 与半规管的几何形状有关的框架和 眼外肌，这些参照系有一个解剖学上的 在小脑的模块化组织中的对应物。模块化的 大脑皮质中的组织在解剖学上是可区分的 含有生理上不同的攀缘纤维的隔间和它们的 相关的浦肯野细胞。这些模块是由平行编织在一起的 穿过几个模块的光纤。在大多数情况下， 实验方法是将手法进行细胞外记录 浦肯野细胞的活动通过自然视觉、前庭和 本体感觉刺激。上升和上升的相对贡献 颗粒细胞轴突的平行纤维段与浦肯野的发生 通过记录多个单位的颗粒细胞来评估细胞的简单棘波 麻醉兔浦肯野细胞的活性和单细胞活性 对眼外本体感受器的刺激作出反应。分布情况 这一活性将与下列絮状组件相关确定 不同地控制特定的眼外肌。如果，如 假设，特定眼部肌肉的伸展会激活颗粒细胞 只有在那些控制肌肉的模块中，然后分布 各个模块上的浦肯野细胞活动将提供对 颗粒细胞轴突的两部分相对影响。一种类似的 研究将使用自然视觉刺激来调查 研究结果的概括性。两项研究将提供一个更统一的观点 攀爬纤维的功能。在一项研究中，眼外本体感觉 在麻醉的兔身上将使用刺激来确定 浦肯野细胞攀升纤维激活的条件 产生简单尖峰调制的短暂增强。在……里面 另一项研究，将记录成对的绒毛状浦肯野细胞 同时在清醒的兔子身上确定容量如何 亚橄榄同步有节律性放电影响 由自然视觉和前庭刺激引起的眼球运动。在……里面 研究絮体参与眼球控制的准备工作 与头部运动相结合的动作，颈部的贡献 肌肉本体感受器对信号处理的研究将由 麻醉和清醒兔浦肯野细胞的记录 它的身体可以绕垂直轴旋转，而头部 静止的。五个絮状组件中的一个与其他四个不同 因为它的攀爬纤维不受视网膜图像运动的调制。 向下橄榄供给部投射的解剖 这个模块的攀升纤维表明它可能与 人们的视线发生了自愿的转移。这一假设将通过记录来评估 从清醒的兔子体内的浦肯野细胞，允许它的头在 垂直轴产生随意的凝视移动，这在兔子 通常发生在眼睛/头部的联合运动中。

The long-term objective is to better understand cerebellar function by investigating the neuronal signal processing underlying eye movements elicited by natural stimulation. The experiments will focus on the flocculus of the rabbit. The central theme is that signal processing in the flocculus entails mapping within and between intrinsic reference frames related to the geometry of the semicircular canals and the extraocular muscles, and that these reference frames have an anatomical counterpart in the modular organization of the cerebellum. The modular organization is seen in the cortex as anatomically distinguishable compartments containing physiologically distinct climbing fibers and their associated Purkinje cells. The modules are woven together by the parallel fibers, which traverse several modules. For the most part, the experimental method will be manipulation of extracellularly recorded Purkinje cell activity by presentation of natural visual, vestibular, and proprioceptive stimuli. The relative contribution of the ascending and parallel fiber segments of granule cell axons to generation of Purkinje cell simple spikes will be assessed by recording multi-unit granule cell activity and single unit Purkinje cell activity in the anesthetized rabbit in response to stimulation of extraocular proprioceptors. Distribution of this activity will be determined in relation to the floccular modules that differentially control particular extraocular muscles. If, as hypothesized, stretch of a particular eye muscle activates granule cells only in those modules that control that muscle, then the distribution of Purkinje cell activity across modules will provide a measure of the relative influence of the two parts of the granule cell axon. A similar study will be done using natural visual stimulation to investigate the generality of the findings. Two studies will provide a more unified view of climbing fiber function. In one study, extraocular proprioceptive stimulation will be used in the anesthetized rabbit to determine the conditions under which climbing fiber activation of Purkinje cells produces a short-lasting enhancement of simple spike modulation. In another study, pairs of floccular Purkinje cells will be recorded simultaneously in the awake rabbit to determine how the capacity of the inferior olive to discharge synchronously and rhythmically is influenced by eye movements evoked by natural visual and vestibular stimuli. In preparation for studying floccular participation in control of eye movements made in combination with head movements, contributions of neck muscle proprioceptors to signal processing will be investigated by recording from Purkinje cells in both the anesthetized and awake rabbit whose body can be rotated about a vertical axis while the head is stationary. One of the five floccular modules differs from the other four because its climbing fibers are not modulated by retinal image motion. The anatomy of the projections to the part of the inferior olive providing the climbing fibers to this module suggests that it may be related to voluntary gaze shifts. This hypothesis will be evaluated by recording from Purkinje cells in the awake rabbit allowed to move its head about the vertical axis to produce voluntary gaze shifts, which in the rabbit normally occur as combined eye/head movements.