A Computational Model of the Eye Movement Effects on Motion Perception

Accurate speed and direction matches can be made between a moving stimulus viewed with a stationary eye and a moving stimulus viewed with an eye moving in the opposite direction to the stimulus. However, when the eye moves in the same direction as the distal stimulus, at a slower speed, subjects match the retinal-image motions of the stimuli rather than their distal motions (Heidenreich and Turano, 1995 Investigative Ophthalmology and Visual Science 36 1675). Furthermore, it is only under this latter condition (and when the eye is stationary) that subjects can precisely discriminate distal stimulus speeds (Turano and Heidenreich Vision Research in press).

We present a computational model that can account for the results of all three findings. The model assumes that the extraretinal signal mirrors the eye movement. Motion information from the retinal and extraretinal sources is combined in a subtractive manner when the two signals have opposite sign. When the two signals have the same sign, they do not combine, and motion judgments are based solely on information from the retinal source.