Two pathways transmitting vestibulospinal influences from the lateral vestibular nucleus of Deiters to Extensor Fusimotor Neurones.

Abstract

In precollicular decerebrate cats repetitive stimulation of the lateral vestibular nucleus causes acceleration of the discharge of primary and secondary endings of muscle spindles of the ipsilateral gastrocnemius muscle. The spindle excitation outlasts the stimulus and the extrafusal contraction. This long-lasting effect is abolished by barbiturates leaving only an initial excitation which runs parallel with muscle tension record. While this effect is indicative of the depressant action exerted directly or indirectly by barbiturates on spinal internuncials transmitting vestibular excitation to fusimotor neurones, the persistent initial excitation suggests the existence of a more direct pathway from Deiters' nucleus to fusimotor neurones. This pathway is probably monosynaptic as that described for α motoneurones by Lund and Pompeiano.