Convergence and Interaction of Vestibular and Deep Somatic Afferents Upon Neurons in the Vestibular Nuclei of the Cat

Abstract

1. In Flaxedil cats 149 neurons in the vestibular nuclei were examined with optic, acoustic, vestibular (labyrinthine polarization) and adequate somatosensory stimuli. 2. 128 neurons, which were fully examined, were analyzed for their patterns of response. 126 units responded to vestibular stimuli, 104 of these to somatic and vestibular. 2 neurons responded to somatic stimuli exclusively and none to optic or acoustic. 3. The vestibular results support the concept that the anatomically defined intervestibular (commissural) fibres are functionally significant. The probable semicircular canal or otolith origins of the various vestibular responses are discussed. 4. The somatic influence was almost joint movement specific. Evidence gathered from animals submitted to cerebellectomy or barbiturate anaesthesia supports tlie concept of a direct proprioceptive somatosensory influence upon the vestibular nuclei. 5. The possible significance of the findings concerning postural and oculomotor mechanisms is discussed.