Influence of vestibulo-ocular reflex gain on human optokinetic responses.

In 15 patients with severe bilateral vestibular impairment (mean vestibulo-ocular reflex (VOR) gain less than 0.05), constant velocity optokinetic nystagmus (OKN) gain, optokinetic after nystagmus (OKAN) initial velocity, and OKAN duration were significantly (p less than 0.0025) lower than in 20 normal subjects of similar age. In the normal subjects VOR gain was significantly correlated (p less than 0.05) with OKAN initial velocity but not with OKAN duration or OKN gain. The results of this study provide additional evidence for the existence in human subjects of an optokinetic pathway whose function, like that of the subcortical optokinetic pathway in animals, varies with VOR gain.