Figure 1. Motion stimulus design for 2D/3D-motion localizers and opponent motion.

(A) 2D-motion localizer. Dots alternated from moving (inward, outward, clockwise, or counterclockwise) to static in 15 s blocks across the run. A fixation cross was located at the screen center. (B) 3D-motion localizer stimulus design (changing-disparity-defined stereomotion). Dots were binocularly presented. Red dots depict those presented to the right eye, and green dots depict those presented to the left eye. Red/green colors are used here for illustration. Dots displayed in blocks as either coherent stereomotion (perceived as 3D motion toward (1 s) – away (1 s) in a central disk and away (1 s) – toward (1 s) in a surrounding annulus) or temporally non-coherent (scrambled) motion in 10 s blocks across the run. In both conditions the dots’ x-y coordinates were shuffled every stereo frame pair, the only difference was whether the disparity changed coherently or randomly (temporally scrambled order of stereo frame pairs). All dot pairs moved together in both conditions. (C) Opponent-motion stimulus design. Dots displayed in blocks as either unpaired (15 s) or paired (15 s). In both conditions, half of the dots moved rightward and half the dots moved leftward. For illustration, the dots were color coded in this panel by motion direction (red/blue); note that in the actual experiment all dots were white regardless of the motion direction and condition. In the unpaired condition, the dots’ positions were random. In the paired condition, the two dots within a given pair had the same y-coordinates and were never more than 0.5 deg apart.