Three-dimensional organization of vestibular-related eye movements to off-vertical axis rotation and linear translation in pigeons

During linear accelerations, compensatory reflexes should continually occur in order to maintain objects of visual interest as stable images on the re tina. In the present study, the three-dimensional organization of the vesti bule-ocular reflex in pigeons was quantitatively examined during linear acc elerations produced by constant velocity off-vertical axis yaw rotations an d translational motion in darkness. With off-vertical axis rotations, sinus oidally modulated eye-position and velocity responses were observed in all three components, with the vertical and torsional eye movements predominati ng the response. Peak torsional and vertical eye positions occurred when th e head was oriented with the lateral visual axis of the right eye directed orthogonal to or aligned with the gravity vector, respectively. No steady s tate horizontal nystagmus was obtained with any of the rotational velocitie s (8-58 degrees/s) tested. During translational motion, delivered along or perpendicular to the lateral visual axis, vertical and torsional eye moveme nts were elicited. No significant horizontal eye movements were observed du ring lateral translation at frequencies up to 3 Hz. These responses suggest that, in pigeons, all linear accelerations generate eye movements that are compensatory to the direction of actual or perceived tilt of the head rela tive to gravity. In contrast, no translational horizontal eye movements, wh ich are known to be compensatory to lateral translational motion in primate s, were observed under the present experimental conditions.