Miall R C, Weir D J, Wolpert D M, Stein J F
Oxford University, University Laboratory of Physiology, Parks Road, Oxford, OX1 3PT, U.K.
J Mot Behav. 1993 Sep;25(3):203-16. doi: 10.1080/00222895.1993.9942050.
The motor system may use internal predictive models of the motor apparatus to achieve better control than would be possible by negative feedback. Several theories have proposed that the cerebellum may form these predictive representations. In this article, we review these theories and try to unify them by reference to an engineering control model known as a Smith Predictor. We suggest that the cerebellum forms two types of internal model. One model is a forward predictive model of the motor apparatus (e.g., limb and muscle), providing a rapid prediction of the sensory consequences of each movement. The second model is of the time delays in the control loop (due to receptor and effector delays, axonal conductances, and cognitive processing delays). This model delays a copy of the rapid prediction so that it can be compared in temporal register with actual sensory feedback from the movement. The result of this comparison is used both to correct for errors in performance and as a training signal to learn the first model. We discuss evidence that the cerebellum could form both of these models and suggest that the cerebellum may hold at least two separate Smith Predictors. One, in the lateral cerebellum, would predict the movement outcome in visual, egocentric, or peripersonal coordinates. Another, in the intermediate cerebellum, would predict the consequences in motor coordinates. Generalization of the Smith Predictor theory is discussed in light of cerebellar involvement in nonmotor control systems, including autonomic functions and cognition.
运动系统可能会使用运动器官的内部预测模型，以实现比负反馈所能达到的更好的控制。有几种理论提出，小脑可能形成这些预测表征。在本文中，我们回顾这些理论，并试图通过参考一种称为史密斯预估器的工程控制模型将它们统一起来。我们认为，小脑形成两种类型的内部模型。一种模型是运动器官（如肢体和肌肉）的前向预测模型，可对每次运动的感觉后果进行快速预测。第二种模型是控制回路中的时间延迟模型（由于感受器和效应器延迟、轴突传导以及认知处理延迟）。该模型会延迟快速预测的副本，以便能在时间上与运动的实际感觉反馈进行对齐比较。这种比较的结果既用于纠正表现中的错误，也用作学习第一种模型的训练信号。我们讨论了小脑可以形成这两种模型的证据，并提出小脑可能至少持有两个独立的史密斯预估器。一个在小脑外侧，会以视觉、自我中心或个人周边坐标预测运动结果。另一个在小脑中位，会以运动坐标预测后果。鉴于小脑参与非运动控制系统，包括自主功能和认知，我们还讨论了史密斯预估器理论的推广。
