Processing Shape, Motion and Three-dimensional Shape-from-motion in the Human Cortex

• Published in: Cerebral cortex (New York, N.Y. 1991) N.Y. 1991), 2003-05, Vol.13 (5), p.508-516
• Main Authors: Murray, Scott O., Olshausen, Bruno A., Woods, David L.
• Format: Article
• Language: English
• Subjects: Brain Mapping - methods; Form Perception - physiology; Humans; Motion Perception - physiology; Photic Stimulation - methods; Visual Cortex - physiology
• ISSN: 1047-3211; 1460-2199; 1460-2199
• DOI: 10.1093/cercor/13.5.508

Shape and motion are complementary visual features and each appears to be processed in unique cortical areas. However, object motion is a powerful cue for the perception of three-dimensional (3-D) shape, implying that the two types of information—motion and form—are well integrated. We conducted a series of fMRI experiments aimed at identifying the brain regions involved in inferring 3-D shape from motion cues. For each subject, we identified regions in occipital–temporal cortex that were activated when perceiving: (i) motion in unstructured random-dot patterns, (ii) 2-D and 3-D line drawing shapes, and (iii) 3-D shapes defined by motion cues (shape-from-motion, SFM). We found closely adjacent areas in the lateral occipital region activated by random motion and line-drawing shapes. In addition, we found that the SFM stimuli produced a greater MRI signal in only one of the areas identified with the random motion and line-drawing stimuli: the superior lateral occipital (SLO) region. High-resolution analysis showed that SFM objects and line drawings were processed in separate but adjacent sub-regions in SLO, suggesting that SLO codes object shape but retains topographic segregation based on shape cues. Expanding the analysis to the entire cortex identified a parietal area that had overlapping activation for both SFM and line drawings and increased MRI signal for 3-D versus 2-D shapes, suggesting this area is important for processing shape information.