ROLE OF THE CEREBELLUM IN REACHING MOVEMENTS IN HUMANS - I - DISTRIBUTED INVERSE DYNAMICS CONTROL

This study focuses on the role of the motor cortex, the spinal cord an d the cerebellum in the dynamics stage of the control of arm movement. Currently, two classes of models have been proposed for the neural co ntrol of movements, namely the virtual trajectory control hypothesis a nd the acquisition of internal models of the motor apparatus hypothesi s. In the present study, we expand the virtual trajectory model to who le arm reaching movements. This expanded model accurately reproduced s low movements, but faster reaching movements deviated significantly fr om the planned trajectories, indicating that for fast movements, this model was not sufficient. These results led us to propose a new distri buted functional model consistent with behavioural, anatomical and neu rophysiological data, which takes into account arm muscles, spinal cor d, motor cortex and cerebellum and is consistent with the view that th e central nervous system acquires a distributed inverse dynamics model of the arm. Previous studies indicated that the cerebellum compensate s for the interaction forces that arise during reaching movements, We show here how the cerebellum may increase the accuracy of reaching mov ements by compensating for the interaction torques by learning a porti on of an inverse dynamics model that refines a basic inverse model in the motor cortex and spinal cord.