Keeping it together: The maintenance of figure-ground segregation in the lateral occipital sulcus

Abstract

An important aspect of visual processing involves binding the elementary features of an object and segregating them from background features. Previous research demonstrated that fragmented line-drawings of objects could be discriminated from a background of randomly orientated lines on the basis of differences in motion. Furthermore, the percept of the object persists for a second or so after motion has stopped. Functional imaging showed that this persistence was reflected in brain activation in area LO but not in MT+ (Ferber et al, 2003). In the present study a comparison was made between the persistence of forms constructed from motion and those constructed from colour/brightness similarity. In the colour/brightness condition the background was a different colour/brightness from the object, but they moved together. Both motion and colour/brightness percepts produced persistence after the motion or colour/brightness cue was removed. Functional imaging showed a gradual increase in the persistence of brain activity in the early visual areas (V1, V2, VP), which reached significance in V4v and peaked in LO. These results suggest that the binding or grouping of visual elements is accomplished early on in the visual pathway, before V4v, and that the maintenance of grouped visual elements in V4v and LO is independent of cue type.