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Abstract

Perception of object motion requires that the visual system integrates shape and motion information about objects. However, recent fMRI studies have implicated separate human brain regions in the analysis of motion (MT/MST) and shape (lateral occipital complex-LOC). We tested whether MT/MST is involved in the analysis of both object shape and motion using fMRI. We observed higher responses to intact than scrambled images of objects in the LOC and MT/MST, especially in a ventral subregion of MT/MST, suggesting that regions involved mainly in the processing of visual motion are also engaged in the analysis of object shape. These object selective responses in MT/MST were observed for moving objects and static 3D objects defined by disparity or shading but not for 2D silhouettes of objects. In contrast, these object selective responses were observed in the LOC for all of these object types. Further studies tested responses to shapes defined by different cues (i.e. disparity, motion or shading) by using event-related fMRI adaptation. Lower responses for the same shape defined by different cues than two different consecutively-presented stimuli implicate neural representations of shapes independent of the cues that define their contours. Our findings suggest differential processing of visual shape in the LOC and MT/MST.