Three-Dimensional Computation during Off-Vertical Axis Rotation (OVAR) in Monkeys

抄録

In order to study how dorso-ventral and naso-occipital linear accelerations affect the ocular responses induced by inter-aural axis linear accelerations, three-dimensional cyclic modulation of eye positions and velocities during off-vertical axis rotation (OVAR) were analyzed in four rhesus monkeys. The animals were rotated in darkness at 60°/s about an earth horizontal axis while placed in a pitched position relative to the rotation axis, so that the plane in which the gravitational vector rotated around the head was varied while the acceleration applied along the inter-aural axis remained identical across different pitch conditions. The amplitude of the compensatory bias slow phase eye velocity was the largest when the gravitational vector rotated in a plane between the animals' stereotaxic horizontal and presumed utricular planes. The phase of the modulation in yaw (horizontal) slow phase velocity, but not in eye position, tended to lag as the stimulus axis deviated from the normal to the presumed utricular plane. The modulation of roll (torsional) eye position was a function of the interaural acceleration, but the amplitude of modulation of roll slow phase velocity decreased with an increase in the roll bias velocity. Modulation of pitch (vertical) eye position was the largest when the axis of rotation corresponded to the head yaw axis, but modulation of pitch slow phase velocity was the largest during rotation about an axis close to the roll axis. Thus, the time differentiation of the positional modulation did not predict the velocity modulation. It is hypothesized that there are separate pathways for processing cyclic modulations of the eye position and velocity, and that the velocity storage utilizes both utricular and saccular information.