Abstract
A primary function of the visual system is to analyze the trajectories of moving objects. This seemingly simple process is complicated by theoretical considerations, which show that measurements of the velocity of a moving object are inevitably confounded with the spatial arrangement of its edges. This type of confusion is likely to be detrimental to an organism's survival, and so must be resolved. This review describes some recent experiments that demonstrate the existence and time-course of a solution in the visual cortex of the macaque brain. Related work on perception, behavior, and computational theory is discussed.