EFFECT OF SECTION OF VESTIBULAR NERVE UPON CORTICALLY INDUCED MOVEMENT IN CAT

Abstract

The effect of unilateral vestibular nerve section on cortically induced movement was studied in acute experiments in 22 cats anesthetized with Dial. Cortically induced flexor movements were markedly diminished or abolished by section of the 8th nerve ipsilateral to the movement, but were less influenced by section of the contralateral 8th nerve. Extensor responses were reduced by section of either the ipsilateral or contralateral 8th nerve. The reduction in amplitude of the muscular response often does not occur until some minutes after nerve section. Markedly increasing the strength of cortical stimulation may mask or compensate for the facilitation lost by vestibular nerve section. The results suggest that the vestibular facilitation demonstrated is mediated predominantly through the facilitatory system of the bulbar reticular formation rather than over vestibulo-spinal paths. It is concluded that the vestibular nerves contribute afferent impulses which maintain a certain background activity in some part of the brain stem facilitatory system.