Compensatory eye movements during voluntary head and neck movements.

We studied compensatory eye movements during passive and active head rotation using the video head impulse test in 5 healthy human subjects. In passive trials, compensatory eye movements occurred with a median latency of 16 ms following the onset of leftward and rightward head movements, and the median velocity gain was 0.94. In contrast, in active trials, the latencies of compensatory eye movements were reduced (median 4 ms) and the velocity gains were increased (median 1.08). We found similar reductions in latency and increases in gain of compensatory eye movements in active trials compared with those in passive trials without a visual target. The present results suggest the potential contribution of corollary discharge of voluntary head and neck movements to compensatory eye movements, consistent with findings in monkey experiments.