The role of smooth pursuit in suppression of post-rotational nystagmus

Some authors have suggested that the smooth pursuit system (SPS) may be responsible for nystagmus suppression when a small visual target--stationary with respect to a subject receiving vestibular stimulation in the dark--is presented. Under five experimental conditions, post-rotational vestibular stimulations were combined in different ways with the presentation of a small visual target. The oculomotor responses of 15 normal subjects were recorded and analyzed. The characteristics of nystagmus suppression (latency, dynamics, and nonlinear behaviour) seem to be consistent with the hypothesis of SPS participation. A nonlinear mathematical model of the interaction between vestibulo-ocular reflex and SPS is presented. Computer simulation of the experimental conditions considered in this study provides theoretical results which closely approximate the actual experimental data.