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Sean MacEvoy, Russell Epstein; Position-Invariant fMRI adaptation effects in scene-selective regions. Journal of Vision 2007;7(9):1046. doi: 10.1167/7.9.1046.
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© ARVO (1962-2015); The Authors (2016-present)
Complex visual scenes preferentially activate several areas of the human brain, including the parahippocampal place area (PPA), a portion of the retrosplenial complex (RSC), and a region near the transverse occipital sulcus (TOS). Many basic response properties of these regions remain unknown, including the extent to which they are visuotopically organized. Recent fMRI studies have shown that PPA and TOS are particularly sensitive to stimuli presented in the visual periphery (Levy et al. 2001, 2004), consistent with the idea that neurons in these regions possess large receptive fields that integrate information from across the visual field. To test this hypothesis directly, we adapted an fMRI approach employed recently to analyze visual topography in the object-selective lateral occipital complex (LOC) (McKyton and Zohary 2006). We compared activity evoked by sequences of photographs of indoor and outdoor scenes confined to either the left or right visual hemifields, as well as the magnitude of adaptation produced by identical preceding stimuli in the same or opposite hemifield. We found that RSC responses did not distinguish between stimuli falling in either the ipsi- or contralateral hemifields, while PPA and TOS displayed small but significant preferences for contralateral stimuli. However, in all three areas, adaptation effects were position-invariant: responses to stimuli in one hemifield were equivalently reduced following adaptation to stimuli in either the same or opposite hemifield. In contrast to LOC, where a prior study observed adaptation between stimuli appearing in the same hemifield only, these results indicate that scene-selective neurons in PPA, RSC and TOS possess receptive fields covering large regions of visual space that include significant portions of both hemifields.
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