Is facilitation responsible for the "motion induction" effect

When a horizontal bar is presented after a single dot is shown at one of its ends, an illusory motion is seen which has been dubbed "motion induction" in the literature. The phenomenon has been attributed to a facilitation process which asymmetrically modulates the inputs to motion detectors, for instance by some sort of changes in processing speed. Computer simulations of motion detector arrays show, however, that this basic effects has to be expected from the properties of simple motion detectors. It has been recently reported that the strength of the illusory motion increases with the subjective salience of the inducing element. New computer simulations demonstrate that this observation can be related to the control of the local gain of motion detector input signals by the feature contrast in a particular region of the stimulus. High-level attentional mechanisms or changes in transmission speed are not required to explain these phenomena. The implications of such local gain-control mechanisms for our understanding of second-order motion perception are discussed.