Inhibitory interaction between channels sensitive to direction and velocity in the human visual system.

Two paradigms for the study of velocity contrast have been employed. Paradigm one has focused on perceived velocity changes across a field. Paradigm two has focused on perceived velocity changes at the juncture of disparate velocities. The current experiments employ both paradigms to look at oppositely directed motion. Using paradigm two, it was determined that, with oppositely directed motion, the effect on perceived velocity could not be attributed to lateral inhibitory interaction--in contrast to earlier reports of lateral interaction when motion was in the same direction. Using paradigm one, it was determined that the effect upon perceived velocity with oppositely directed motion appeared to involve inhibition across entire fields of motion.