On the distribution of fast-phase intervals in optokinetic and vestibular nystagmus.

Histograms of fast-phase intervals in human optokinetic and vestibular nystagmus were generated, and fitted to statistical distributions used in previous studies. The distributions did not depend on stimulation type (optokinetic or vestibular). An inverse Gaussian or a gamma distribution fitted the data better than did a reciprocal Gaussian distribution, but none fitted the data especially well. In some cases, however, the interpretation of these distributions is more physiologically satisfactory than in others. Recommendations are made on which class of models is preferred, and the experiments needed to support the particular models. Our results call into question the validity of previous studies that fit statistical distributions to data sets of a size comparable to ours.