Kenyon G T, Medina J F, Mauk M D
Department of Neurobiology and Anatomy, University of Texas Medical School at Houston 77030, USA.
J Comput Neurosci. 1998 Mar;5(1):17-33. doi: 10.1023/a:1008874209991.
We use a mathematical model to investigate how climbing fiber-dependent plasticity at granule cell to Purkinje cell (gr-->Pkj) synapses in the cerebellar cortex is influenced by the synaptic organization of the cerebellar-olivary system. Based on empirical studies, gr-->Pkj synapses are assumed to decrease in strength when active during a climbing fiber input (LTD) and increase in strength when active without a climbing fiber input (LTP). Results suggest that the inhibition of climbing fibers by cerebellar output combines with LTD/P to self-regulate spontaneous climbing fiber activity to an equilibrium level at which LTP and LTD balance and the expected net change in gr-->Pkj synaptic weights is zero. The synaptic weight vector is asymptotically confined to an equilibrium hyperplane defining the set of all possible combinations of synaptic weights consistent with climbing fiber equilibrium. Results also suggest restrictions on LTP/D at gr-->Pkj synapses required to produce synaptic weights that do not drift spontaneously.
我们使用一个数学模型来研究小脑皮质中颗粒细胞到浦肯野细胞（gr-->Pkj）突触处依赖攀缘纤维的可塑性如何受到小脑-橄榄系统突触组织的影响。基于实证研究，假设gr-->Pkj突触在有攀缘纤维输入时激活会使其强度降低（长时程抑制，LTD），而在无攀缘纤维输入时激活则会使其强度增加（长时程增强，LTP）。结果表明，小脑输出对攀缘纤维的抑制与LTD/P相结合，将自发攀缘纤维活动自我调节到一个平衡水平，在该水平上LTP和LTD达到平衡，并且gr-->Pkj突触权重的预期净变化为零。突触权重向量渐近地局限于一个平衡超平面，该超平面定义了与攀缘纤维平衡一致的所有可能突触权重组合的集合。结果还表明，为了产生不会自发漂移的突触权重，gr-->Pkj突触处的LTP/D存在限制。
