Figure 2.

Apparatus for the oculomotor experiment. A, Display screen, LED array, subject, and eye tracker. The subject was positioned on a bite bar in front of the display screen and LED array. He/she wore the Eyelink II tracker. The display screen was used for calibrating the tracker. The LED array was used to present fixation targets: one straight ahead (red) and the others at six peripheral locations (green). The central LED was colinear with the midpoint of the subject's interocular axis and a normal from the midpoint of the display screen. The distance from the subject to the LED array was 50, 100, or 200 cm. The array could rotate about its midpoint, thereby creating meridians of different orientations. B, Closeup of hot mirrors and aperture-occluder. In the monocular condition, we mounted an annular occluder with a small aperture on the far side of the mirror and in front of the nondominant eye. That eye could see the initial fixation target through the aperture but could not see the peripheral targets. C, Tested field positions: six meridians (0°, 30°, 60°, 90°, 120°, and 150°) each with six eccentricities (±2°, ±4°, and ±8°).