Location and spatial profile of category-specific regions in human extrastriate cortex

Authors

  • Mona Spiridon,

    Corresponding author
    1. Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts
    2. Neurology & Imaging of Cognition Laboratory, Department of Neurosciences, University of Geneva, Switzerland
    • Neurology & Imaging of Cognition Lab, Department of Neurosciences, University Medical Center (CMU), 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
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  • Bruce Fischl,

    1. Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts
    2. Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts
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  • Nancy Kanwisher

    1. Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts
    2. Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts
    3. McGovern Institute for Brain Research, Cambridge, Massachusetts
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Abstract

Subjects were scanned in a single functional MRI (fMRI) experiment that enabled us to localize cortical regions in each subject in the occipital and temporal lobes that responded significantly in a variety of contrasts: faces > objects, body parts > objects, scenes > objects, objects > scrambled objects, and moving > stationary stimuli. The resulting activation maps were coregistered across subjects using spherical surface coordinates [Fischl et al., Hum Brain Mapp 1999;8:272–284] to produce a “percentage overlap map” indicating the percentage of subjects who showed a significant response for each contrast at each point on the surface. Prominent among the overlapping activations in these contrasts were the fusiform face area (FFA), extrastriate body area (EBA), parahippocampal place area (PPA), lateral occipital complex (LOC), and MT+/V5; only a few other areas responded consistently across subjects in these contrasts. Another analysis showed that the spatial profile of the selective response drops off quite sharply outside the standard borders of the FFA and PPA (less so for the EBA and MT+/V5), indicating that these regions are not simply peaks of very broad selectivities spanning centimeters of cortex, but fairly discrete regions of cortex with distinctive functional profiles. The data also yielded a surprise that challenges our understanding of the function of area MT+: a higher response to body parts than to objects. The anatomical consistency of each of our functionally defined regions across subjects and the spatial sharpness of their activation profiles within subjects highlight the fact that these regions constitute replicable and distinctive landmarks in the functional organization of the human brain. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc.

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