Figure 1.

Depiction of the experimental timing during trials involving head motion. At the start of each trial, gaze was centered at 0°, 20° up, or 20° down. In a randomly chosen two thirds of the trials for each starting vertical eye position, the visual target moved randomly up or down with equal probability at a selected time interval before or slightly after onset of whole-body rotation, to evoke a saccade during the horizontal VOR slow phase. The interval between target motion and body rotation was systematically varied to obtain vertical saccades occurring at various horizontal eccentricities evoked by the horizontal VOR. To avoid predictive effects, the visual target remained motionless in a randomly chosen one third of trials.