Neocerebellum and Motor Programming: Evidence from Reaction-Time Studies in Monkeys with Dentate Nucleus Lesions
CNRS - INP
Clinical and experimental data point to the participation of the neocerebellum and particularly of the dentate nucleus (DN) in the generation of limb movements. The purpose of the present contribution was to investigate the contribution of the DN to the specification of movement parameters and in the releasing of motor programs. This role was analyzed in baboons performing goal-directed responses. More precisely the effects of DN dysfunction on the latency of pointing movements, with variable amplitude or direction, were studied. Changes in reaction times, observed under different experimental conditions, are discussed in view of the role usually attributed to the neocerebellum in motor preparation and programming. The present data suggest a critical involvement of the DN in the processes preceding the triggering of limb movements, although the possible participation of the DN in controlling ongoing responses should also be considered.
The conception that the neocerebellum is one of the main structures involved in the generation and triggering of voluntary movements has given rise to much debate since the idea was re-formulated by Evarts and Thach in 1969. A large number of clinical and experimental data argue in favor of the involvement of the neocerebellar structures in the nervous processes taking place before and during the execution of movement. The question therefore arises as to which specific operation the neocerebellum is responsible for. In the framework of a three-stage model of motor organization, for instance, (cf. Requin, 1980) one might wonder