Canal-otolith interactions after off-vertical axis rotations. II. Spatiotemporal properties of roll and pitch postrotatory vestibuloocular reflexes.
We have examined the spatiotemporal characteristics of postrotatory eye velocity after roll and pitch off-vertical axis rotations (OVAR). Three rhesus monkeys were placed in one of 3 orientations on a 3-dimensional (3D) turntable: upright (90 degrees roll or pitch OVAR), 45 degrees nose-up (45 degrees roll OVAR), and 45 degrees left ear-down (45 degrees pitch OVAR). Subjects were then rotated at +/-60 degrees /s around the naso-occipital or interaural axis and stopped after 10 turns, in one of 7 final head orientations, each separated by 30 degrees . We found that postrotatory eye velocity showed horizontal-vertical components after roll OVAR and horizontal-torsional components after pitch OVAR that varied systematically as a function of final head orientation. The quantitative analysis suggests that, in contrast to the analogous yaw OVAR paradigm, a system of up to 3 real, gravity-dependent eigenvectors and eigenvalues determines the spatiotemporal characteristics of the residual eye velocities after roll and pitch OVAR. One of these eigenvectors closely aligned with gravity, whereas the other 2 determined the orientation of the earth horizontal plane. We propose that the spatial characteristics of eye velocity after roll and pitch OVAR follow the physical constraints of stationary orientation in a gravitational field and reflect the brain's best estimate of head-in-space orientation within an internal representation of 3D space.
Hess
Bernhard J M
BJ
Department of Neurology, University of Zürich, Zürich, Switzerland. bhess@neurol.unizh.ch
Jaggi-Schwarz
Karin
K
Misslisch
Hubert
H
D000818:Animals; D008253:Macaca mulatta; D008954:Models, Biological; D009760:Nystagmus, Physiologic / Q000502:physiology*; D009949:Orientation / Q000502:physiology*; D010037:Otolithic Membrane / Q000502:physiology*; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D012399:Rotation; D013028:Space Perception / Q000502:physiology*