Surround-contingent tilt aftereffect

We investigated whether aftereffects can be contingent on surroundings. Gabor patches tilted clockwise and counterclockwise were presented in alternation. Each patch was surrounded by an open circle or an open square. After prolonged exposure to these stimuli, tilt aftereffects were found to be contingent upon the surrounding frames: Vertical test patches appeared tilted clockwise when surrounded by the frame that was presented in conjunction with the adaptation patch tilted counterclockwise. The effect lasted 24 hours and was observed only when adaptation and test stimuli were presented at the same retinotopic position, but not observed at the same spatiotopic position. These results indicate that the aftereffect would be influenced not only by stimulus features but also by their surroundings.