Abstract
Previous studies have suggested the existence of several distinct motion-detectors in the visual system; such as the first-order detector, the second-order detector, and the feature-tracker. However, it is not clear how these motion detectors are involved in visual-awareness. One way to verify the problem is to measure the magnitude of motion aftereffects(MAE) under binocular rivalry suppression (BRS)(Blake & Fox, 1974). In previous studies however, adaptation stimulus were not completely suppressed and the relation of visual awareness and motion detectors remains controversial.
Here, we developed a powerful variant of continuous flash suppression (Tsuchiya & Koch, 2005) where motion stimulus can be erased from conscious awareness for several tens of seconds. We measured the magnitude of both static and flicker MAE under normal viewing and BRS conditions. Two types of motion were used for adaptation; 2f+3f-motion and 1f-motion. In 2f+3f-motion, direction of first-order motion is opposite to that of higher-order motion which observers perceived dominantly.
Psychophysical results indicate that for 2f+3f-motion adaptation, flicker MAE completely vanishes under BR suppression, while it decreases but does not dissappears for 1f-motion adaptation. On the other hand, static MAE occurred in both 2f+3f-motion and 1f-motion adaptation even when observers did not perceive the adaptation presented stimulus at all. Taking into consideration that flicker MAE reflects adaptation of all three motion detectors(Nishida & Ashida, 2001) and that both 1st and 2nd order motion detectors are monocular, our results suggest that higher-order motion-tracker system is highly correlated with visual awareness.