Myograms yielded by faradic stimulation of the cerebellar nuclei

Abstract

Isotonic myograms were recorded of the activity of antagonistic muscles in the fore and hind limbs of decerebrate cats in response to electrical stimulation of the cerebellar nuclei. In the fore limbs, the contractions of the biceps brachii and caput laterale of the triceps brachii were recorded, and in the hind limbs the tibialis anterior and gastrocnemius-soleus. Stimulation of the nucleus dentatus, n. emboliformis, n. globosus or n. fastigii resulted in contraction of the flexor muscles accompanied by reciprocal relaxation of the extensors, the latter resembling the inhibitory relaxation evokable by faradization of the cerebellar cortex. The intensity of the reaction is least on stimulation of the n. dentatus and increases in the order given above. After-discharge is lacking from the nuclear responses in the case of the flexor muscles, while the extensors show a well marked tonus rebound following the period of stimulation. It is concluded that in the normal activities of the animal, flexor tone is increased and antigravity tone decreased by cerebellar function, while antigravity tone is augmented by rebound on suspension of the cerebellar discharge.