Experimental study of otolith-ocular reflex in linear acceleration

Abstract

Of the various reflexes originating from the otolith organ, the reflex corresponding to linear acceleration still remains unexplained in many aspects; above all, the modes of reaction corresponding to an otolithic stimulation and the function of the saccule as an equilibrium regulator are not well studied yet.The present investigations concerning the problems were performed by observing otolith-ocular reflexes under the imposition of linear accelerations to the normal and labyrinthectomized rabbits.When the animals were subjected to linear accelerations, the eye deviation appeared to the directions of repositioning the eye to the normal position, that is, vertical eye deviation in frontal, rotatory eye movement in saggital and vertical eye deviation in axial movement, respectively.The eye deviation did not appear in the purely horizontal plane, and the eye deviation and the acceleration were synchronous. Bilaterally labyrinthectomized animals did not show the eye deviation corresponding to the acceleration while the eye deviation was of normal pattern in unilaterally labyrinthectomized animals.Bilateral sacculotomy resulted in the disappearance of eye deviation in axial direction with the reflexes in the other two directions preserved.Thus, it was found that the otolith organ provoked the eye movement to the direction opposite to the body movement and that the otolith organ of one side regulated the ocular movement bilaterally.It was also confirmed that the saccule participated in the regulation of equilibrium and that the shear of the otolith membrane against the macula seemed to be the most important stimulation for the otolith-ocular reflex in linear acceleration ; the utricle in frontal direction, the utricle and saccule in saggital direction and the saccule in axial direction, respectively.