The perception of moving stimuli: a model of spatiotemporal coding in human vision.

An empirically plausible extension of the Marr and Ullman (1981) [Proc. R. Soc. Lond. B 211, 151-180 (1981)] model for coding movement direction uses the magnitude of spatial and temporal response derivatives to encode the speed as well as the direction of movement. The performance of the model is illustrated for drifting edges of different spatial scales and the properties of the components which separately compute the two derivatives are respectively compared to individual channels of the conventional pattern and flicker systems.