[The velocity storage mechanism in human optokinetic nystagmus]

The velocity storage mechanism was studied in 12 normal human subjects. For optokinetic stimulation, we principally used step stimuli of 80 deg/sec generated by an Ohm type optokinetic stimulation drum. The charge characteristics of the velocity storage mechanism in the human optokinetic nystagmus were closely approximated by the first-degree delay formula having an average time constant of 26.1 sec. This value was much longer than that reported in other animals. The OKN slow phase eye velocity reached nearly 100% of the stimulus velocity immediately after the onset of stimuli. Then, the velocity gradually decreased during first 30 seconds to approximately 70% of the stimulus velocity, and it increased again to velocity the initial during the next 50-60 seconds of the continuous stimuli. These findings, indicating the characteristics specific in the human OKN may be related to the long time constant in the charge characteristics in human OKN as compared to other animals.