Figure 1.

3D motion and stimulus ensemble. A, Relationship between 3D motion trajectories and the retinal motion they induce. Motion straight toward a point between the observer's eyes provides equal and opposite motion signals to the two eyes (orange). Oblique trajectories can cause motion in the same direction but with different speeds in the two eyes (white). Frontoparallel motion (blue) provides similar motion signals to the two eyes. B, The stimulus ensemble used to probe 3D motion tuning in area MT. Matrix schematic of fully crossed monocular velocity pairings (x- and y-axes; ±1, 2, 10°/s, or [B]lank), presented at six grating orientations (depicted as repeated planes with corresponding grating icons). Conditions consisting of frontoparallel motion are indicated by blue; conditions consisting of equal and opposite motion in the two eyes, which would be induced by motion directly toward or away from the observer, are indicated in orange; conditions consistent with oblique 3D trajectories are shown in white; monocular stimulus conditions in gray.