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Nicolas Davidenko, Kevin Weiner, Kalanit Grill-Spector; Parametric face-to-hand transformations reveal shape-tuned representations in human high-level visual cortex.. Journal of Vision 2012;12(9):1176. doi: 10.1167/12.9.1176.
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Previous fMRI studies (e.g., Weiner & Grill-Spector, 2010; 2011) document alternating and adjacent face- and limb-selective regions throughout human ventral temporal and lateral occipitotemporal cortices (Figure 1a), but the functional properties of these regions remain poorly understood. Because localizer images typically differ in many low-level, textural and global properties, it is unclear what aspects of face or limb images drive responses in these regions. Further, it is unknown whether responses in adjacent face- and limb-selective patches are driven by stimulus properties or by the perceived category of the stimulus (or whether the relative contribution of these factors differs across regions). Building on the face silhouette methodology (Davidenko, 2007; Davidenko, Remus, & Grill-Spector, 2011), we generated a novel set of parameterized silhouette stimuli that span a continuous morph space between faces and hands, while their low-level properties are well controlled (Figure 1b). We defined stimuli at 5 morph levels, ranging from fully face-like (level-1) to fully hand-like (level-5), and behaviorally calibrated intermediate (level-3) stimuli to appear equally face-like and hand-like. In an fMRI block-design experiment, we measured the mean BOLD response in face- and limb-selective regions as participants observed these stimuli. We found that responses in face-selective regions in the middle (mFus-faces) and posterior (pFus-faces) fusiform gyrus and inferior occipital gyrus (IOG-faces) decrease monotonically as stimuli become less face-like and more hand-like. In contrast, responses in nearby limb-selective regions in the occipital temporal sulcus (OTS-limbs), inferior temporal gyrus (ITG-limbs), lateral occipital gyrus (LOG-limbs) and medial temporal gyrus (MTG-limbs) increase monotonically as stimuli become more hand-like. Our results demonstrate that these face- and limb-selective regions are tuned to stimulus shape and their responses can be parametrically modulated by morphing stimuli away from a preferred category.
Meeting abstract presented at VSS 2012
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