Modification of Constant Optokinetic Nystagmus by Vestibular Stimulation

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Abstract
• Experiments were conducted to quantify the effect of a vestibular stimulation of known magnitude on a constant optokinetic nystagmus (OKN). Ten normal human subjects were tested with varying magnitudes of vestibular stimuli that were superimposed on a constant 30°/s optokinetic stimulus. The gain of the vestibular system in the dark was 0.42 ± 0.11, and the gain in the light during superimposition testing was 0.12 ± 0.02. From these results, predictions were made that the degree of vestibular imbalance necessary to produce an asymmetric OKN would generate a spontaneous nystagmus in the dark, which would be equivalent to 20 to 30°/s. Data from a large group of patients were used for corroboration of the results. (Arch Otolaryngol 105:132-136, 1979)