MIT Department of Electrical Engineering & Computer Science

Cerebellar Mediation of Servo-Control of Voluntary Movement

Steve G. Massaquoi
MIT

Thursday, April 30, 1998
2:00 PM (refreshments 1:45)
Grier Room, Room 34-401B
EECS Special Seminar

Abstract

The anterior cerebellum appears to be a critical facilitator of accurate rapid voluntary movement. Although several models exist, how the neural structure performs this function remains unknown. Because of the many nonlinearities in body mechanics, the measured low stiffness of body parts during natural motions, and the delays associated with neural signal transmission, it has been suggested that the motor system and therefore possibly the cerebellum relies on internal models of body dynamics to implement control. Specific schemes have been previously proposed that incorporate explicit body state estimation and/or nonlinear signal processing. However, the situation may be simpler.

A new model of cerebellar motor control function will be presented that proposes that highly effective feedback control is achieved through linear signal processing and without use of explicit internal models of body dynamics. The core of the model involves the processing of "wave variables" to maintain passive communication between brain and spinal cord and to thereby stabilize feedback control despite signal delays. The limitations in performance of this model and its modifications appear to account for observed imperfections in limb trajectories of healthy human subjects and patients with cerebellar disease. Signals generated by the model during simulation of arm movements resemble several signals observed in the cerebellar nuclei of monkeys performing analogous movements.

The implications of the model for understanding normal and certain types of pathological motor control will be discussed.