The significance of attention and duration of the stimulation in optokinetic nystagmus.

Twenty normal human subjects were exposed to horizontal optokinetic stimulation of (OKN) of one minute's duration. They were instructed either to look attentively at every passing target or to stare unattentively at the moving field. After one week the tests were repeated. Another group received optokinetic training for 10 days. It is concluded that arousal is of decisive importance for the reproducibility of OKN. Diversion of the attention did not cause a change in the neural path from a cortical to a subcortical predominance. The estimate of the velocity of the slow phase (EV) must be based on a sufficiently long period of stimulation. The maximum EV of individual beats was not representative of inattentive OKN. The training effect of OKN was short-lasting and insignificant.