Fig. 2.

Example responses of pattern and component cells to gratings and plaids. A: curves in the center of each stimulus family show the predicted responses of idealized pattern-selective (red) and component-selective (blue) neurons tuned for rightward motion when tested with the stimuli depicted in the ring. These correspond to the conditions used in our experiment. All conditions were tested in 12 directions, although for economy the full set is only shown for the static case. Each column shows responses to a different set of targets. Stationary gratings: MT neurons are generally not strongly responsive or selective for static patterns, so we expect only weak responses, not differing between pattern and component cells and indicated in black. Moving gratings: we expect both pattern and component cells to exhibit a robust unimodal response, represented by the black von Mises function in the center. The motion of each grating is indicated by black arrows. Bikinetic plaids: as in Fig. 1A, these consist of two moving component gratings (the motion of which is indicated by blue arrows) yielding one pattern motion (red arrows). We expect pattern and component cells to exhibit bimodal (component cell) and unimodal (pattern cell) tuning, represented by blue and red von Mises functions. Left- and right-handed unikinetic plaids: as in Fig. 1B, these consist of a moving grating and a stationary one; the left- and right-handed cases differ in which grating is moving. The color scheme is the same as for the bikinetic plaid. We expect both pattern and component cells to exhibit unimodal tuning. The component cells should respond to the moving grating essentially as if the static grating were absent. We therefore expect a difference in preferred direction of 60° between the two kinds of unikinetic plaid. Pattern cells’ tuning should be aligned with the pattern motion, and the difference in preferred directions should be roughly 0°. B–E: responses of 4 representative example cells. Color scheme is same as in A, but pattern and component predictions are depicted by dashed lines, whereas measured responses are solid lines. All cells responded weakly to static gratings and showed classical response characteristics to moving gratings and bikinetic plaids. The component cell (B) responded in a fashion consistent with the component prediction (direction tuning rotation was 52°). The pattern cells (D and E) obeyed the pattern prediction, although not perfectly (direction tuning rotation values of 7° and 16°, respectively). The mixed cell (C) showed classical behavior to moving gratings and bikinetic plaids and would be classified as a pattern cell when stimulated with bikinetic plaids, but when probed with unikinetic plaids, it showed component cell-like behavior (direction tuning rotation of 38°).