Primate translational vestibuloocular reflexes. I. High-frequency dynamicsand three-dimensional properties during lateral motion

Primate translational vestibuloocular reflexes. I. High-frequency dynamics and three-dimensional properties during lateral motion. J. Neurophysiol. 83 : 1637-1647, 2000. The dynamics and three-dimensional (3-D) properties of t he primate translational vestibuloocular reflex (trVOR) for high-frequency (4-12 Hz, +/-0.3-0.4 g) lateral motion were investigated during near-target viewing at center and eccentric targets. Horizontal response gains increas ed with frequency and depended on target eccentricity. The larger the horiz ontal and vertical target eccentricity, the steeper the dependence of horiz ontal response gain on frequency. In addition to horizontal eye movements, robust torsional response components also were present at all frequencies. During center-target fixation, torsional response phase was opposite (antic ompensatory) to that expected for an "apparent" tilt response. Instead tors ional response components depended systematically on vertical-target eccent ricity, increasing in amplitude when looking drown and reversing phase when looking up. As a result the trVOR eye velocity vector systematically tilte d away from a purely horizontal direction, through an angle that increased with vertical eccentricity with a slope of similar to 0.7. This systematic dependence of torsional eye velocity tilt on vertical eye position suggests that the trVOR might follow the 3-D kinematic requirements that have been shown to govern visually guided eye movements and near-target fixation.