Transformation of inputs in the cerebellar internal model

脑小脑被认为是控制自主运动的重要组成部分之一。然而，我们对脑-小脑通讯系统如何促进自主运动的执行知之甚少。毫无疑问，浦肯野细胞是小脑皮层唯一的输出神经元，是该系统中最关键的组成部分之一。我们检测了日本猴子腕部运动的浦肯野细胞简单尖峰的活动。我们训练了三只猴子，让它们用右手腕和操纵杆来执行快速的步跟踪任务。这个任务涉及手腕在8个不同方向的运动，前臂保持不同的姿势。Kakei et al. 1999)。我们记录了任务相关的浦肯野细胞在小叶V和小叶VI半球部分的简单尖峰活动。我们发现，大多数任务相关的浦肯野细胞在运动开始前后的简单尖峰活动有显著的调节，而与wr无关。绝大多数浦肯野细胞在腕关节部分或所有方向的运动开始前，以短暂和急剧减少的简单尖峰活动开始其任务相关的调节。在其中一些浦肯野细胞中，简单尖峰活动的暂时下降伴随着短暂的爆发。另一方面，只有少数浦肯野细胞启动任务相关的简单尖峰活动调节，其在运动开始时增加。这些结果表明，脑小脑浦肯野细胞对小脑核神经元的主要作用是通过解除抑制来促进自主运动的执行。鉴于这一观点，小脑核中的神经元可以在没有苔藓纤维传入侧枝的兴奋性输入的情况下被激活，苔藓纤维传入侧枝的存在一直存在争议或很少（见Ito 2011）。我们的发现将为皮质-小脑通信回路中的信息处理原理提供新的见解。少

The cerebro-cerebellum has been considered as one of the essential components for control of voluntary movement. Nevertheless, we know little about how the cerebro-cerebellar communication system contributes to execution of voluntary movement. There is no doubt that Purkinje cell, the sole output neuron from the cerebellar cortex, is one of the most critical components of the system. We examined activities of simple spikes of Purkinje cells for wrist movement in Japanese monkeys. We trained three monkeys to perform a rapid step-tracking task using the right wrist with a manipulandum. This task involves the performance of wrist movements in 8 different directions with the forearm held in different postures(ref. Kakei et al. 1999). We recorded task-related simple spike activities of Purkinje cells in hemispheric part of lobules V and VI. We found that a majority of task-related purkinje cells had significant modulation of simple spike activities around the movement onset regardless of wr … More ist positions, and there are some patterns of these modulations. A great majority of Purkinje cells initiated their task-related modulation with temporal and sharp decrease of simple spike activities just before movement onset for some or all directions of the wrist movement. In some of these Purkinje cells, the temporal decrease of simple spike activities were followed by a short burst. On the other hand, only a minority of Purkinje cells initiated task-related modulation of simple spike activity with its increase around the movement onset. These results suggest that dominant effect of Purkinje cells in the cerebro-cerebellum on neurons in the cerebellar nuclei is facilitation through disinhibition for execution of voluntary movement. Given this perspective, neurons in the cerebellar nuclei can be activated without excitatory inputs from collaterals of mossy fiber afferents, whose existence has been controversial or minor if any(see Ito 2011 for review). Our findings would provide a new insight about principles of information processing in the cortico-cerebellar communication loop. Less