Vigot Réjan
Division of Speciation Mechanisms I, National Institute for Basic Biology, Nishigonaka 38, Myodaiji-cho, Okazaki 444-8585, Japon.
Med Sci (Paris). 2003 Apr;19(4):437-41. doi: 10.1051/medsci/2003194437.
It is commonly thought that a persistent change in the efficacy of the synaptic transmission is the basic mechanism underlying learning and memory. The cerebellum, key structure of the motor function, exhibits a synaptic plasticity named cerebellar long-term depression or LTD. This phenomenon appears in the Purkinje cell when the two main excitatory inputs (one consists of the parallel fibers which relay information on the task to accomplish and the other one includes the climbing fiber which conveys error signals) are activated in combination, resulting in a persistent decrease of the efficacy of the parallel fiber-Purkinje cell synapse. Studies made in the last 20 years show that activation of ionotropic and metabotropic glutamate receptors triggers complex signal transduction processes, leading to the phosphorylation and the internalization of AMPA receptors, a subtype of glutamatergic receptors. The aim of this paper is firstly to present mechanisms involved in LTD induction and maintenance. The second part introduces briefly experimental data that show that LTD is indeed strongly associated with motor learning. Recent studies on the involvement of the cerebellum in cognitive tasks also suggest that LTD may play some role other than that in the sole motor learning.
人们普遍认为，突触传递效能的持续变化是学习和记忆的基本机制。小脑作为运动功能的关键结构，表现出一种名为小脑长时程抑制（LTD）的突触可塑性。当两个主要的兴奋性输入（一个由传递关于要完成任务信息的平行纤维组成，另一个包括传递误差信号的攀缘纤维）联合激活时，这种现象出现在浦肯野细胞中，导致平行纤维 - 浦肯野细胞突触效能的持续降低。过去20年的研究表明，离子型和代谢型谷氨酸受体的激活触发复杂的信号转导过程，导致AMPA受体（一种谷氨酸能受体亚型）的磷酸化和内化。本文的目的首先是介绍LTD诱导和维持所涉及的机制。第二部分简要介绍了实验数据，这些数据表明LTD确实与运动学习密切相关。最近关于小脑参与认知任务的研究也表明，LTD可能在除单纯运动学习之外还发挥一些作用。
