ABSTRACT

This chapter examines the interaction of two oculomotor subsystems, smooth pursuit and vestibulo-ocular reflex (VOR), during the motor task known as VOR cancellation. VOR clockwise eye velocity was accompanied by horizontal velocity to the left whereas during cancellation clockwise velocity was accompanied by horizontal velocity to the right. A VOR response not obeying Listing’s law at all would be purely torsional and in the opposite direction to the head movement. Torsional stimulation means that during VOR subjects were rotated in the dark around the earth-horizontal, naso-occipital axis while fixating an imagined earth-stationary target at different locations. VOR eye velocity was mainly torsional to compensate for the head rotation. Because gaze is down there was an additional horizontal eye velocity component. In this example, the subject was also looking to the left resulting in some vertical eye velocity. The appearance of the visual target clearly did not cancel torsional eye velocity, but did decrease its magnitude.