Average gross responses of FST neurons (n = 173, A) and MT/V5 neurons (n = 25, B) selective for ridge orientation, to matched ridges (black) and planar surfaces (gray) plotted as a function of the relative orientation of the ridges. Tuning for tilt orientation was nonsignificant (repeated-measures ANOVA) in A but significant in B (F(3,72) = 4.51, p < 0.002).