Abstract
Despite widespread incorporation in theoretical accounts of visual cognition and the apparent ease of humans to employ prepositions (e.g., “above”) or to reason about spatial relations, no neural evidence has ever been reported for structural descriptions (SDs), which make explicit a distinction between the shape of the entities in a scene and the relations between those entities. A number of current theoretical accounts dispense with the distinction all together, assuming that when object A is above object B different features will be defined than when object B is above object A and that explicit relations are only defined at a later stage. Subjects viewed a sequence of two briefly-presented frames, each composed of a pair of separated objects and had to judge whether one of the objects had changed. Switching the relative positions of the objects resulted in a greater release from fMRI-adaptation in the posterior fusiform, an area critical for object recognition, than when the objects were translated to the same extent, indicating explicit representation of relations. Control conditions ruled out explanations that posit global or inter-object features by observing that the greater relational release was maintained even when the objects were embedded in different contexts (gratings varying in scale and orientation) that changed with translation but not with the relational switch. Attentional shifts, eye movements, and foveal overrepresentation were ruled out as possible accounts by showing that the greater release from adaptation was independent of whether the same object was or was not closer to fixation and by showing that the greater release from adaptation was maintained at presentation times as short as 50ms.
NSF BCS 04-20794, 05-31177, 06-17699.