Contextual modulations of center-surround interactions in motion revealed with the motion aftereffect.

Segregation of objects from their backgrounds is one of vision's most important tasks and one that is accomplished with ease. It is often hypothesized that suppressive center-surround receptive field interactions represent a key neural substrate underlying efficient figure-ground segregation, yet this intuitively appealing hypothesis has received very little experimental support. Using the motion aftereffect as an experimental tool, we explored this hypothesis by examining how surround suppression was affected by contextual manipulations that altered the perceived figure-ground relations but kept local motion signals unchanged. The results demonstrated that surround suppression was strong when the visual context implied a large moving field. On the other hand, when the contextual interpretation was consistent with a smaller moving object, surround suppression was greatly reduced. These findings are consistent with the notion that center-surround interactions play a role in segregating moving objects from backgrounds.