The cerebellum as a predictor of neural messages—II. Role in motor control and motion sickness

Abstract

The hypothesis of a “stable estimator” was proposed in the preceding article as a circuit computing an internal estimate of a body movement variable and endowed with regulating properties. Such a circuit would exist for each variable, and would be embedded in a particular folium of the cerebellar cortex and the related paths of the brainstem nuclei and the inferior olive. In this article, the action of the premotor orders on the stable estimator circuit is studied, at initiation and during execution of voluntary movements. A feedback loop via the cerebellar cortex would control on-going movements and maintain the efficacy of the stabilizing sensorimotor reaction, while preventing its interfering with the movement. The regulating loop via the inferior olive would have a short-term role in initiating movements and would boost insufficient stabilizing reactions. The discrepancy between internal estimates of the same variable would be reflected in motion sickness.