Discontinuity limits for the generation of visual motion aftereffects with sine- and square-wave gratings

Visual motion aftereffects (MAE's) were produced with adapting gratings that underwent repeated, abrupt displacements in a uniform direction. MAE's could be generated with sine-wave gratings even when the magnitude of each displacement approached a phase angle as large as 1/2 cycle. The maximum spatial step for generating a MAE with a square-wave grating was less than 1/4 cycle. If a dark pause was introduced between the successive positions (phases) of the adapting grating, MAE's disappeared when the pause was longer than 60-70 msec. The results can be used to define the spatiotemporal-response limits of a short-range motion process (or system of directionally selective motion sensors), and the results also suggest that the individual Fourier components of complex spatial patterns are capable of producing independent signals for direction of motion.