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Abstract
Unitary activities were recorded from the oculo-motor nucleus and optic nerve in rabbits by means of super-fine microelectrodes with the aim of clarifying the neuronal mechanism concerned in the reflex arc of op-tokinetic nystagmus.
1)The unitary activities of oculo-motor neurons when optic nystagmus was elicited were as follows
The discharge rate increased or decreased gradually upon rotating the optical cylinder until it reached a certain rate, which continued to the beginning of nystagmus. the impulse to the ocular muscle which rested in the quick phase decreased promptly to a minimum rate just before the beginning of the quick phase and increased gradually during the slow phase. the change in the discharge rate of the impulses to the ocular muscle which contracted in the quick phase corresponded to the course of nystagmus.
2)The eye speed in the slow phase of nystagmus which was recorded with electronystagmography was accelerated towards the nasal side when discharges of an optic nerve fiber which was presumed to be derived from the temporal side of the fovea were increased, and it decelerated when discharges of an optic nerve fiber which was presumed to be derived from the nasal side of the fovea were increased.
Thus the eye speed in the slow phase was controlled as the image of the stripe of the optical cylinder on the retina would be caught again by the fovea even if the fovea was turned away temporarily from the image.
3)The responses of single optic nerve fibers to a shifting stripe were examined in curarized rabbits. Some units reacted a different way according to the shifting direction of the stripe and some units reacted the same way. in some units the responses were caused only by shifting in one direction.