The tonic oculomotor function of the cervical joint and muscle receptors

Cases of peripheral labyrinthine lesions were examined by stimulation of the cervical joint and muscle receptors. Head-chin (HC) position to one side induced compensatory oculomotor tone (ipsilateral nystagmus), which depended on the function of the horizontal canal of that side. This compensatory tone increased the duration of the optokinetic after-nystagmus (OKAN), with stripes moving contralaterally to the HC position. Isometric contraction of the muscles which rotate the HC to one side induced ipsilateral oculomotor tone (contralateral nystagmus), which depended on the function of the utricle acting in the same direction. In one case, the muscle-induced tone increased the frequency of the OKN with the slow phase in the same direction; in another, it prolonged the slow-phase pursuit interval. In the absence of a vestibular component, distortion of the OKN was induced.