T15Measurement of Motion Detection Thresholds under Natural and Manipulated Retinal Image Motion Conditions

摘要

Despite retinal image motion caused by fixational jitter, the world appears stable. Previous studies from our lab found that targets that slip on the retina in a direction consistent with eye motion - even if they are amplified - are perceived as stationary or moving less than for other directions of motion. We now establish a quantitative measure of how these percepts affect the detection of motion. Real-time retinal tracking and targeted stimulus delivery using an AO Scanning Laser Ophthalmoscope enables us to present any stimulus motion including natural, stabilized, amplified, and rotated trajectories. Three subjects performed a 2AFC task judging clockwise or counterclockwise motion of a stimulus under stable and amplified motion conditions in directions consistent with and opposite natural eye motion. Stimuli were presented extrafoveally to avoid fixation tracking. The smallest thresholds occurred under natural eye motion conditions (a??0.8 arcmin). When the magnitude of retinal motion was equal but opposite natural motion, thresholds were a??3 times larger. When the retinal stimulus slip was doubled, thresholds were only a??2 times larger. The visual system perceives true motion of objects despite confounding motion of their retinal images, but only when that confounding motion's direction is consistent with fixational eye motion.