Eye Movements from Single Utricular Nerve Stimulation In The Cat

TLDR

Electrical stimulation of single utricular nerves in the cat, with varying stimulation frequency, was used to examine changes in extraocular muscle tension. The stimulation produced almost pure rotational eye movements with ipsilateral upward and contralateral downward shifts, slight contralateral horizontal shifts, and muscle tension changes strongest in the ipsilateral superior oblique and contralateral inferior oblique; the utricular‑ocular reflex responded across frequencies up to 1600 cps, whereas the cupulo‑ocular reflex did not respond well to high frequencies, and temporal summation differed among vestibulo‑ocular reflex systems.

Abstract

Single utricular nerves were electrically stimulated in the cat. The induced eye movements were almost pure rotation in both eyes. In addition to rotation, there were upward shifts in the ipsilateral eye and downward shifts in the contralateral eye. Slight contralateral horizontal shifts occurred in both eyes. Tension increases in extraocular muscles were strongest in the ipsilateral superior oblique and contralateral inferior oblique. They were weaker in the ipsilateral superior rectus and contralateral inferior rectus, and were weakest in the ipsilateral medial rectus and contralateral lateral rectus muscles. The tension increase in the contralateral inferior oblique and the lateral rectus was studied by changing the frequency of stimulation. The utricular-ocular reflex reacted from very low to very high frequencies, as high as 1600 cps. In comparison, the cupulo-ocular reflex arc did not respond well to high frequencies. The temporal summation in the vestibulo-ocular reflexes appeared different between the utricular, the vertical ampullary and the lateral ampullary systems.