Reflex Eye Movements Induced by Stimulation of the Semicircular Canal Nerve in Rabbits

가토반규관신경자극(家兎半規管神經刺戟)에 의(依)한 반사성안구운동기전(反射性眼球運動機轉)에 관(關)하여

According to recent observations of Cohen et al. the patterns of vestibular eye movements of rabbits are different from those of cats. However, the causes of such difference of the reflex eye movements in these species are not wholly explained. While the accumulated data obtained from cats appear to be established, experimental evidences in rabbits are rather meager. The author had re-examined the reflex eye movements of rabbits and attempted to find a mechanism which causes such difference in the reflex eye movements between two species. In anesthesized rabbit, unilateral individual semicircular canal nerve was stimulated selectively with a fine insulated electrode which was inserted through a hole made on the corresponding osseous canal, under a dissecting microscope. When an individual canal nerve was stimulated, the reflex movements of both eyes were observed, photographed, and recorded kymographically. Extraocular muscles were also studied to find their morphological characteristics and to correlate them with the function of the muscles. 1. At the beginning of the stimulation, both eyes moved to a specific direction depending upon the canal stimulated, and such directional eye movements were sustained during the whole course of stimulation. Amplitude of the eye movement showed graded responses to the increasing frequency of the stimulus, reaching to the maximal response at 200-300 cps. 2. Stimulation of the unilateral horizontal canal nerve caused conjugate eye movements, which was also observed in cats and other species by other investigators. 3. Stimulation of the unilateral vertical canal nerve caused a pattern of non-conjugate eye movements, which are different from those observed in cats. Such different patterns of vestibular eye movements in two different species are ascribable to the functional difference of the inferior and superior oblique muscles.