[Horizontal optokinetic nystagmus in the pigeon during static tilts in the frontal plane]

The influences of the static whole body roll tilts (30 or 45 degrees) on horizontal optokinetic nystagmus (HOKN) produced by optokinetic stimuli at a constant velocity (16 or 30 degrees/sec) were examined in the 16 pigeons. The significant tilt-dependent asymmetry of the tonic otolith effects on optokinetic system was revealed which consists in pronounced inhibitory effect of the right-hand tilts unlike the left-hand tilts on HOKN. Separate recording of the oculomotor responses from the right and left eyes showed that during static roll tilts the temporonasal-nasotemporal (TN-NT) asymmetry of HOKN normally existing in the pigeon remained for the eye disposed above and was replaced by symmetric pattern for the eye disposed below. The results suggest the mechanism of TN-NT asymmetry is controlled by the otolith inputs and its function can be essentially modified under the influence of otolith membranes reorientation in gravity.