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Soo Jin Park, Helene Intraub, David Widders, Do-Joon Yi, Marvin M. Chun; Boundary extension: Filling-out scene layout information in human parahippocampal cortex. Journal of Vision 2006;6(6):802. doi: 10.1167/6.6.802.
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© ARVO (1962-2015); The Authors (2016-present)
A central question in visual cognition is how we perceive a seamless world despite physiological constraints in vision. Here, we report functional magnetic resonance imaging (fMRI) evidence for boundary extension (BE: Intraub & Richardson, 1989), the extrapolation or “filling-out” of scene layout beyond what was physically presented. FMRI adaptation reveals whether a particular neuronal population treats two stimuli as the same or different (Grill-Spector et al., 1999; Kourtzi & Kanwisher, 2001). We used fMRI adaptation to measure whether the parahippocampal place area (PPA), important for scene layout perception (Epstein & Kanwisher, 1998), would respond to extrapolated layout. In the two critical conditions, close-up and wide-angle views of the same scene were presented in one of two different orders: close-wide, or wide-close. If the PPA activity reveals BE and responds to the filled-out layout of the scene representation, then we should observe attenuation in the close-wide condition but not in the wide-close condition. FMRI revealed boundary extension for close-wide scene pairs in the PPA. As a control, we also measured responses in the lateral occipital complex (LOC), which processes object information. No BE is predicted in the LOC because behavioral work suggests that extrapolation does not occur for object representations alone. Indeed, fMRI adaptation did not reveal any extrapolation of object representations in the LOC. Thus, scene layout representations are extrapolated beyond the confines of the perceptual input selectively in the PPA. Such filling-out may facilitate perception of a continuous world from discontinuous, constrained views.
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