Data from: Learning from the past: a reverberation of past errors in the cerebellar climbing fiber signal

The cerebellum allows us to rapidly adjust motor behavior to the needs of the situation. It is commonly assumed that cerebellum-based motor learning is guided by the difference between the desired and the actual behavior, i.e., by error information. Not only immediate but also future behavior will benefit from an error because it induces lasting changes of parallel fiber synapses on Purkinje cells (PCs), whose output mediates the behavioral adjustments. Olivary climbing fibers, likewise connecting with PCs, are thought to transport information on instant errors needed for the synaptic modification yet not to contribute to error memory. Here, we report work on monkeys tested in a saccadic learning paradigm that challenges this concept. We demonstrate not only a clear complex spikes (CS) signature of the error at the time of its occurrence but also a reverberation of this signature much later, before a new manifestation of the behavior, suitable to improve it.

小脑（cerebellum）可帮助机体根据情境需求快速调整运动行为。学界普遍认为，基于小脑的运动学习由期望行为与实际行为之间的差值，即误差信息，所引导。误差不仅能使即时行为获益，还可对未来行为产生积极影响——因为它会诱导浦肯野细胞（Purkinje cells, PCs）上平行纤维突触发生持久性改变，而浦肯野细胞的输出正是介导行为调整的关键。同样与浦肯野细胞形成突触连接的橄榄小脑攀缘纤维（olivary climbing fibers），此前被认为仅负责传递突触修饰所需的即时误差信息，并不参与误差记忆的形成。本文报道了一项在猕猴中开展的眼跳学习范式（saccadic learning paradigm）实验研究，该研究对上述经典观点提出了挑战。我们不仅观测到误差发生时刻清晰的复杂 spike（complex spikes, CS）特征信号，还发现该特征信号会在行为的新一次表现出现前的较长时段内持续回响，这一发现恰好可用于优化后续行为。