FIG. 2.

Example of 3D eye movements in response to sinusoidal stimulation about different axes. A Vertical axis in the light (upper panels) and in the dark while the subject imagined a target (lower panels). B Horizontal axis oriented at 45° azimuth. Upper panels, light; lower panels, dark. Left side panels in A and B show the stimulus (S), torsion (T), vertical (V), and horizontal (H) eye position signals. The right side panels show the corresponding angular velocities. Saccadic peak velocities are clipped in the plots. In this and all subsequent figures, eye positions and velocities are expressed in a right-handed, head-fixed coordinate system. In this system clockwise, down and left eye rotations viewed from the perspective of the subject are defined as positive values (see also Fig. 1). Note that for easier comparison, the polarity of the stimulus signal has been inverted.