[Study of optokinetic nystagmus and spino-motor functions with cyclo-rotatory optokinetic stimulus]

It has been shown that the neural channels from the otolith organs and the vertical semicircular canals connect to the cyclo-rotatory oculomotor system. However, only a few studies have been conducted to examine the relationship between the cyclo-rotatory optokinetic (COK) and the vestibular inputs. Accordingly, we have analyzed the cyclo-rotatory oculomotor output evoked by a COK stimulus, in 30 subjects; 21 normal adults, 4 elderly persons, and 5 persons with unilateral vestibular dysfunction. In addition, the spinal motor output was simultaneously recorded and comparatively analyzed. The increase in COK nystagmus (COKN) was less than that in horizontal and vertical OKN. There was a significant decline in the maximum slow phase eye velocity in the elderly subjects as well as in the subjects with unilateral vestibular dysfunction, compared to that in the normal adult subjects. Regarding the spinal motor output, in the subjects with unilateral vestibular dysfunction, a pronouned increase in the sway distance from the center of gravity was found with COK stimulus forward the lesioned side. However, with the COK stimulus, there was no significant correlation between the output functions of the cyclorotatory oculomotor system and those of the spinal motor system.