Reproducibility of Duration of Postacceleratory Nystagmus

Abstract

Two groups, each consisting of 22 subjects, were rotated in both the clockwise and counterclockwise direction in three successive, identical accelerations. The strengths of stimulus used were 1, 2, 4 and 8°/sec². The duration of nystagmus (denoted as the after-discharge) was measured after each acceleration. It was found that the mean duration was longest in the first test, and then decreased successively on repeated stimulation. The decrease was most pronounced at 1 and 2°/sec². The interindividual variation was consistently slightly less at the higher strengths of stimulus, with a concurrent marked decrease in the intraindividual variation. The mean difference was small in a comparison between the results of clockwise and counterclockwise acceleration on repeated stimulation. The calculated borderline values show that the difference between clockwise and counterclockwise acceleration was smallest at the higher strengths of stimulus. This also applied to the calculated borderline values in the second and third tests. Large individual deviations were, however observed. It is discussed whether the pendulum function of the cupula-endo-lymph system may be correlated to the nystagmus reflex. It is concluded that the nystagmus reflex may possibly reflect the movements of the cupula-endolymph system at accelerations of 1-4°/sec², but that the central nervous influence results in shorter after-discharges than could be expected at accelerations of 4-8°/sec².