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Cerebral Cortex Advance Access published online on October 24, 2007
Cerebral Cortex, doi:10.1093/cercor/bhm162
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© The Author 2007. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org

A Dynamic Object-Processing Network: Metric Shape Discrimination of Dynamic Objects by Activation of Occipitotemporal, Parietal, and Frontal Cortices

Johannes Schultz1, Lewis Chuang1 and Quoc C. Vuong1,2

1 Department of Cognitive and Computational Psychophysics, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 2 Division of Psychology, Newcastle University, Newcastle upon Tyne, UK

Address correspondence to Quoc C. Vuong, Division of Psychology, Henry Wellcome Building for Neuroecology, Framlington Place, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK. Email: q.c.vuong{at}ncl.ac.uk.

Shape perception is important for object recognition. However, behavioral studies have shown that rigid motion also contributes directly to the recognition process, in addition to providing visual cues to shape. Using psychophysics and functional brain imaging, we investigated the neural mechanisms involved in shape and motion processing for dynamic object recognition. Observers discriminated between pairs of rotating novel objects in which the 3-dimensional shape difference between the pair was systematically varied in metric steps. In addition, the objects rotated in either the same or the different direction to determine the effect of task-irrelevant motion on behavior and neural activity. We found that observers' shape discrimination performance increased systematically with shape differences, as did the hemodynamic responses of occipitotemporal, parietal, and frontal regions. Furthermore, responses in occipital regions were only correlated with observers' perceived shape differences. We also found different effects of object motion on shape discrimination across observers, which were reflected in responses of the superior temporal sulcus. These results suggest a network of regions that are involved in the discrimination of metric shape differences for dynamic object recognition.

Key Words: fMRI • metric shape • motion • object recognition • parametric design • psychophysics

Both the first and the third author contributed equally to this work.


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