Optimization of voluntary movements in the cerebellum

Abstract

Voluntary goal-directed movements, such as arm reaching, are nearly optimized in terms of smoothness over the entire movement. Such smoothness is lost with cerebellar dysfunction, suggesting the essential role of the cerebellum in optimizing movement. However, it is still not clear how the cerebellum contributes to achieving this smoothness over an entire movement. A recent study³ has shown that such smoothness of movement can be achieved by reducing the variance of errors at the end of the movement. The author proposes a novel hypothesis that the terminal errors conveyed by climbing fibers in the cerebellum⁴ serve to reduce not only the mean error, but also the variance of the error, through a process analogous to the random walk through movement control candidates. The validity of the hypothesis will be tested by constructing an artificial cerebellum that follows the principles of the random walk hypothesis.