REVERSED VISUAL-MOTION AND SELF-SUSTAINING EYE OSCILLATIONS

A random-dot field undergoing counterphase flicker paradoxically appea rs to move in the same direction as head and eye movements, ie opposit e to the optic-flow field. The effect is robust and occurs over a wide range of flicker rates and pixel sizes. The phenomenon can be explain ed by reversed phi motion caused by apparent pixel movement between su ccessive retinal images. The reversed motion provides a positive feedb ack control of the display, whereas under normal conditions retinal si gnals provide a negative feedback. This altered polarity invokes self- sustaining eye movements akin to involuntary optokinetic nystagmus.