Abstracts
Résumé
Le cervelet, partie du cerveau qui coordonne la fonction motrice, a un rôle clé dans l’apprentissage moteur, voire dans certains processus cognitifs. Il est aujourd’hui couramment admis que la modification à long terme de l’efficacité de la transmission synaptique est la base cellulaire de la mémoire et de l’apprentissage. La cellule de Purkinje, élément central de l’organisation cyto-architectonique du cervelet et de la fonction cérébelleuse, est le siège d’une plasticité neuronale particulière appelée « dépression à long terme ». En quoi consiste cette « dépression »? Quels en sont les mécanismes cellulaires et moléculaires? Quels éléments permettent de considérer que cette plasticité est le mécanisme de base de l’apprentissage moteur? Telles sont les questions abordées dans cet article.
Summary
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.
Appendices
Références
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