[Relation of optokinetic nystagmus and the width of the visual field]

Optokinetic nystagmus (OKN) was elicited in humans by a moving vertical grating wide 30-170 degrees. A large range of velocities (10-120 degrees/sec) and a constant spatial stimulus frequency (0.13 cycle/degree) were used. It has been shown that the qualitative and quantitative OKN parameters can be controlled by stimulus area width. The optimal OKN was found under conditions of the whole field stimulation. Progressive masking of the periphery caused a OKN reduction whose magnitude was fixed in different stimulus ranges. The elimination of central stimulation resulted in a complete OKN suppression. The role of the stimulation eccentricity and of the stationary edges in the observed OKN changes is discussed. The findings offer a possibility for a more precise evaluation of OK responses.