Inter-saccadic interval analysis of optokinetic nystagmus

Abstract Optokinetic nystagmus from healthy human subjects was recorded at different intensity levels elicited by different speeds of the optokinetic stimulus. The time intervals between the onset of consecutive fast components were analyzed and a characteristic pattern of variation in the interval histogram was observed. As the intensity of nystagmus decreased, the interval histogram changed from being symmetric mono-modal, to asymmetric mono-modal and finally to a multi-modal form in which the high order modes were approximately integral multiples of the basic mode. This characteristic change was distinctly altered when the subject followed the optokinetic stimulus voluntarily. The findings lead to new hypotheses about the nystagmus mechanism.