Herzfeld David J, Kojima Yoshiko, Soetedjo Robijanto, Shadmehr Reza
Department of Biomedical Engineering, Laboratory for Computational Motor Control, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Department of Physiology and Biophysics, Washington National Primate Center, University of Washington, Seattle, Washington 98195, USA.
Nature. 2015 Oct 15;526(7573):439-42. doi: 10.1038/nature15693.
Execution of accurate eye movements depends critically on the cerebellum, suggesting that the major output neurons of the cerebellum, Purkinje cells, may predict motion of the eye. However, this encoding of action for rapid eye movements (saccades) has remained unclear: Purkinje cells show little consistent modulation with respect to saccade amplitude or direction, and critically, their discharge lasts longer than the duration of a saccade. Here we analysed Purkinje-cell discharge in the oculomotor vermis of behaving rhesus monkeys (Macaca mulatta) and found neurons that increased or decreased their activity during saccades. We estimated the combined effect of these two populations via their projections to the caudal fastigial nucleus, and uncovered a simple-spike population response that precisely predicted the real-time motion of the eye. When we organized the Purkinje cells according to each cell's complex-spike directional tuning, the simple-spike population response predicted both the real-time speed and direction of saccade multiplicatively via a gain field. This suggests that the cerebellum predicts the real-time motion of the eye during saccades via the combined inputs of Purkinje cells onto individual nucleus neurons. A gain-field encoding of simple spikes emerges if the Purkinje cells that project onto a nucleus neuron are not selected at random but share a common complex-spike property.
精确的眼球运动执行严重依赖于小脑，这表明小脑的主要输出神经元浦肯野细胞可能预测眼球运动。然而，对于快速眼球运动（扫视）的这种动作编码仍不清楚：浦肯野细胞在扫视幅度或方向方面几乎没有一致的调制，关键的是，它们的放电持续时间比扫视持续时间更长。在这里，我们分析了行为猕猴（恒河猴）动眼蚓部的浦肯野细胞放电，发现了在扫视期间活动增加或减少的神经元。我们通过它们向尾侧顶核的投射估计了这两类细胞群的综合效应，并发现了一种单峰群体反应，该反应精确地预测了眼球的实时运动。当我们根据每个细胞的复合峰方向调谐来组织浦肯野细胞时，单峰群体反应通过增益场乘法性地预测了扫视的实时速度和方向。这表明小脑在扫视期间通过浦肯野细胞到单个核神经元的联合输入来预测眼球的实时运动。如果投射到核神经元上的浦肯野细胞不是随机选择的，而是具有共同的复合峰特性，就会出现单峰的增益场编码。
