Optokinetic response and visual suppression of the vestibulo-ocular reflex in the open loop condition in the cat

Optokinetic nystagmus (OKN), vestibulo-ocular reflex (VOR) and the visual suppression of the VOR were investigated before and after elimination of retinal image motion following monocular surgical paralysis. Monocular paralysis gave rise to an instability of eye position in the dark which was abolished during the illumination of the mobile but not the immobile eye. In the open-loop condition there was a substantial increase in the monocular OKN gain and a large asymmetry with respect to temporo-nasal and naso-temporal stimulation. Viewing a head-fixed world through a completely paralysed eye suppressed the VOR. This visual suppression was asymmetric and the asymmetry was consistent with that found in the open-loop OKN. These results imply that in the cat visual system, cancellation models of visual suppression of the VOR need to be expanded to accommodate signals generated by stable retinal images.