Cerebral Cortex Advance Access published online on February 14, 2008
Cerebral Cortex, doi:10.1093/cercor/bhn002
The Extraction of 3D Shape from Texture and Shading in the Human Brain
1 Laboratorium voor Neuro- en Psychofysiologie, Katholieke Universiteit Leuven School of Medicine, Campus Gasthuisberg, B-3000 Leuven, Belgium, 2 Department of Psychology, The Ohio State University, Columbus, OH 43210, USA, 3 Department of Radiology, Universitair Ziekenhuis Gasthuisberg, UZ Gasthuisberg, B-3000 Leuven, Belgium
Address correspondence to Prof. Dr Guy A. Orban, Laboratorium voor Neuro- en Psychofysiologie, O&N2, Herestraat 49, bus 1021, Katholieke Universiteit Leuven School of Medicine, Campus Gasthuisberg, B-3000 Leuven, Belgium. Email: guy.orban{at}med.kuleuven.be.
We used functional magnetic resonance imaging to investigate the human cortical areas involved in processing 3-dimensional (3D) shape from texture (SfT) and shading. The stimuli included monocular images of randomly shaped 3D surfaces and a wide variety of 2-dimensional (2D) controls. The results of both passive and active experiments reveal that the extraction of 3D SfT involves the bilateral caudal inferior temporal gyrus (caudal ITG), lateral occipital sulcus (LOS) and several bilateral sites along the intraparietal sulcus. These areas are largely consistent with those involved in the processing of 3D shape from motion and stereo. The experiments also demonstrate, however, that the analysis of 3D shape from shading is primarily restricted to the caudal ITG areas. Additional results from psychophysical experiments reveal that this difference in neuronal substrate cannot be explained by a difference in strength between the 2 cues. These results underscore the importance of the posterior part of the lateral occipital complex for the extraction of visual 3D shape information from all depth cues, and they suggest strongly that the importance of shading is diminished relative to other cues for the analysis of 3D shape in parietal regions.
Key Words: 3D shape fMRI human shading texture