Figure 5. Motion-energy mechanism:

(A) Schematic diagram of a motion energy unit: Moving stimulus is convolved with two filters that are odd and even symmetric spatially and temporally oriented filters, then the outputs are squared and summed to create a phase-independent motion energy response. (B) Motion energy units used in the model. At each spatial location there were 16 preferred directions, 5 spatial frequencies, and 5 temporal frequencies. (C) An array of 51,984,000 motion energy units uniformly covering the whole stimulus were applied to the change at each pair of 199 frames. At each location, the preferred velocity of the highest responding motion energy unit from the array was selected as the population response. Motion vectors from physically rotating (D) and wobbling (E) ring pairs are predominantly orthogonal to contours instead of in the rotation direction. (F) The difference between the two vector fields is negligible. Since the flows for physically rotating and wobbling circular rings are almost identical, other factors must govern the perceptual shift from wobbling to rotation at slower speeds.