Surround-contingent motion aftereffect

We investigated whether motion aftereffects (MAE) can be contingent on surroundings. Random dots moving leftward and rightward were presented in alternation. Moving dots were surrounded by an open circle or an open square. After prolonged exposure to these stimuli, MAE were found to be contingent upon the surrounding frames: dots moving in a random direction appeared moving leftward when surrounded by the frame that was presented in conjunction with rightward motion. The effect lasted for 24h and was observed when adapter and test stimuli were presented not only retinotopically, but also at the same spatiotopic position. Furthermore, the effect was observed even when the adapter and test stimuli were presented at different retinotopic and spatiotopic positions as long as they were presented in the same hemi-field. These results indicate that MAE would be influenced not only by the stimulus features, but also by their surroundings, and they suggest that the surround-contingent MAE might be mediated in the higher stage of the motion processing pathway.