Reflex Actions of the Anterior Semicircular Canals on the Clavotrapezius and Extraocular Horizontal Rectus Muscles in Cats

ABSTRACT

Electromyographic responses of the clavotrapezius and extraocular horizontal rectus muscles to the stimulations of the anterior semicircular canal nerves were observed to expore the funtional relationships between the canals and these canals muscles 1. The clavotrapezius muscle was inhibited stimulating the ipsilateral anterior canal nerve and excited by stimulating the contralateral anterior canal nerve. These responses were reversed by stimulating of the functionally paired posterior canal nerves. 2. During the clavotrapezius muscle responded to a prolonged stimulation of the ipsilateral anterior canal nerve, a superimposed stimulation of the contralateral anterior canal nerve reversed the initial response. 3. The medial rectus muscle was excited and the lateral rectus muscle was Inhibition by simulating the ipsilateral anterior canal nerve, and these responses were reversed by stimulating the contralateral canal nerve. Based on these results, it is concluded showing the functional connections between the receptor canals anti the effector muscles for the vestibuloocular and vestibulocollic reflexes, that the excitatory neural pathways from the vestibular nucleus to the cervical and ocular motoneurons are crossed to the opposite side, whereas the inhibitory from the nucleus to these axial motoneurons are uncrossed.