ABSTRACT
There are two visual mechanisms for detecting movement. Movement of an image across retina when the eye is stationary is detected by parvocellular and magnocellular ganglion cells. However, this background stimulation is not essential for the perception of movement since the efferent neural signals which control the voluntary movement of the eyes provide information about movement. When two lights, separated in space, are switched on and off in sequence, it is possible to induce an illusion of movement whereby the light is seen to move from one location to another. It appears that apparent movement is mediated by two separate mechanisms. The perception of movements made by other human beings is known as biological motion. Such films record the movement of parts of the body relative to each other but contain no other visual information. However, when stationary, the patterns of light do not resemble a human form, demonstrating that it is the movement that is typical of human gait.
