Chen Xiang Yang, Wolpaw Jonathan R
Laboratory of Nervous System Disorders, Wadsworth Center, New York State Department of Health and State University of New York at Albany, Albany, New York 12201-0509, USA.
Learn Mem. 2005 May-Jun;12(3):248-54. doi: 10.1101/lm.91305.
While studies of cerebellar involvement in learning and memory have described plasticity within the cerebellum, its role in acquisition of plasticity elsewhere in the CNS is largely unexplored. This study set out to determine whether the cerebellum is needed for acquisition of the spinal cord plasticity that underlies operantly conditioned decrease in the H-reflex, the electrical analog of the spinal stretch reflex. Rats in which the cerebellar output nuclei dentate and interpositus (DIN) had been ablated were exposed for 50 d to the H-reflex down-conditioning protocol. DIN ablation, which in itself had no significant long-term effect on H-reflex size, entirely prevented acquisition of a smaller H-reflex. Since previous studies show that corticospinal tract (CST) transection also prevents down-conditioning while transection of the rubrospinal tract and other major descending tracts does not, this result implies that DIN output that affects cortex is essential for generation of the CST activity that induces the spinal cord plasticity, which is, in turn, directly responsible for the smaller H-reflex. The result extends the role of the cerebellum in learning and memory to include participation in induction of plasticity elsewhere in the CNS, specifically in the spinal cord. The cerebellum might simply support processes in sensorimotor cortex or elsewhere that change the spinal cord, or the cerebellum itself might undergo plasticity similar to that occurring with vestibulo-ocular reflex (VOR) or eyeblink conditioning.
虽然关于小脑在学习和记忆中的作用的研究已经描述了小脑内部的可塑性，但其在中枢神经系统其他部位可塑性形成中的作用在很大程度上尚未得到探索。本研究旨在确定小脑对于脊髓可塑性的形成是否必要，而脊髓可塑性是操作性条件反射下H反射（脊髓牵张反射的电模拟）降低的基础。将小脑输出核齿状核和间位核（DIN）被切除的大鼠暴露于H反射下调方案50天。DIN切除本身对H反射大小没有显著的长期影响，但完全阻止了较小H反射的形成。由于先前的研究表明，皮质脊髓束（CST）横断也会阻止下调，而红核脊髓束和其他主要下行束的横断则不会，因此这一结果意味着影响皮质的DIN输出对于诱导脊髓可塑性的CST活动的产生至关重要，而脊髓可塑性又直接导致了较小的H反射。这一结果将小脑在学习和记忆中的作用扩展到包括参与中枢神经系统其他部位（特别是脊髓）可塑性的诱导。小脑可能只是支持感觉运动皮层或其他改变脊髓的部位的过程，或者小脑本身可能经历类似于前庭眼反射（VOR）或眨眼条件反射中发生的可塑性变化。
