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Alexander Bratch, Stephen Engel, Philip Burton, Daniel Kersten; The Fusiform Body Area Represents Spatial Relationships Between Pairs of Body Parts. Journal of Vision 2018;18(10):408. doi: https://doi.org/10.1167/18.10.408.
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Two regions critical for human body perception have been identified in human visual cortex: the extrastriate body area (EBA; Downing et al., 2001) and the fusiform body area (FBA; Peelen and Downing, 2005). While a wealth of evidence suggests that these areas process individual body parts and whole bodies, respectively, the regions' precise roles have yet to be elucidated. Here, we hypothesized that while neurons in the EBA represent individual body parts, neurons in the FBA not only represent whole bodies, but also represent connections between pairs of body parts. We tested this hypothesis by measuring neural responses to body parts that were perceived as either connected or as two disjoint parts. We used 3 Tesla fMRI (2.4 mm isotropic resolution, TE = 30.4 ms, TR = 2 s, multiband factor = 3) to measure BOLD activity in human subjects (N = 8). In an event-related paradigm, a hand and an elbow were presented within circular apertures on a gray background. The parts were presented either in their "normal" connected positions, or rotated within the apertures to induce the percept of disconnected arm parts. Six rotations were used. We observed significantly higher activity in the FBA, but not the EBA, when subjects perceived the parts as connected as opposed to disconnected, averaging across all rotations. When connectedness was perceived in the most physically ambiguous stimulus rotation, activity increased in both lower-level (V2, V3) and higher-level areas (left and right EBA, FBA). Furthermore, a linear support-vector machine discriminated the pattern of activity for parts perceived as connected vs disconnected at a level above chance in the FBA but not the EBA. Together, these findings strongly suggest that the activity in the FBA underlies the perception of spatial relationships between pairs of body parts.
Meeting abstract presented at VSS 2018
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