Evidence for Separate Movement and Form Channels in the Human Visual System

Two experiments are described which investigated the possibility that the directional and form aspects of a moving stimulus are coded in separate neural locations. The experiments employed an adaptation paradigm in which sensitivities to grids in optimal apparent movement were measured following an adaptation exposure to a grid in real movement. The postadaptation grids possessed varying degrees of similarity to the adaptation stimulus: they could either have a similar orientation and a similar movement direction, or they could differ on just one of these dimensions, or they could differ on both of these dimensions. Selective adaptation effects were observed which were interpreted as supporting the hypothesis that different form and movement channels exist in the human visual system.