[Study of dynamic counterrolling of the eye--quantitative analysis of effects by visual and vestibular systems]

Dynamic counterrolling of the eye is induced when the head is tilted to one side: it includes cyclorotatory nystagmus, which is affected by visual and vestibular systems. Both of these two ocular movements were measured quantitatively through a video recording system, and the role of visual and vestibular systems in visual stabilization was analyzed. The relationship between the optokinetic and vestibulo-ocular systems was variable in relation to the velocity of head tilting. The optokinetic system contributed more in slow head tilting. As the velocity of head tilting increased, the suppression by the optokinetic system was decreased and eventually the vestibulo-ocular system became more dominant. This suggests that the role of visual and vestibular systems in head tilting is similar to that in head rotation. Visual and vestibular systems seem to work together mutually with some individual variation in stabilizing vision with sensory control in the higher level of the visual cortex.