[Babinski and movement synergism].

Babinski's hypothesis that the cerebellum plays an important role in controlling movement synergies is re-interpreted in the light of more recent neurophysiological data. Originally Babinski derived the concept of synergy from the study of movement kinematics, but today, synergy implies an underlying combination of simultaneous muscular activities. It is suggested that the fundamental unit of muscular synergy is the reciprocal inhibition or the co-contraction of antagonist muscles. Various experimental data suggest that an increase in Purkinje cell discharge decreases muscular activity and relaxes antagonist muscles. Inversely, a decrease of cerebellar cortical efferent activity increases nuclear excitability and as a result the long descending motor pathways. Consequently the cerebellum, by controlling joint stiffness through the level of co-contraction in antagonist muscles, would have a significant action in directing multi-joint movement and postural adjustments.