Involvement of the inferior olivary neurons in vestibular compensation

Vestibular decompensation induced by spinal cord transection in left labyrinthectomized guinea pigs provoked asymmetrical excitability of the inferior olivary nuclei. In the right nucleus, spinal deafferentation induced a significantly increased response to electrical stimulation of the contralateral radial nerve and decreased response to ipsilateral radial nerve stimulation. In the left nucleus, opposite results were obtained. Increased responses were recorded in the I.O. neurons during electrical stimulation of the radial nerve ipsilateral to a previous hemilabyrinthectomy, and reduced responses during the electrical stimulation of the radial nerve of the opposite side. Since the inferior olive impinges on the vestibular nuclei both directly and indirectly through the cerebellar loop, it is possible that the inferior olive is involved in the spinal compensation of the vestibular deficits resulting from the hemilabyrinthectomy.