Abstract
For several decades, many studies designed to understand scene processing have focused on three relatively large cortical areas: the parahippocampal place area (PPA), retro-splenial cortex (RSC), and transverse occipital cortex (TOS). Using conventional imaging techniques (with considerable spatial smoothing), these studies have not reported smaller scene-selective cortical sites whose detection relies on visualizing high spatial details. In this study, we demonstrate the first evidence for a fine-scale scene-selective site, located within the human posterior intraparietal gyrus (pIPG) based on: (i) high-resolution fMRI (7T; voxel size = 1 mm isotropic) with no smoothing, and (ii) conventional fMRI (3T; voxel size = 3 mm isotropic) with limited smoothing (<2 mm). In all subjects tested (n = 46; 23 female; aged 22-45), we identified pIPG near (but outside) the tip of the parieto-occipital sulcus and adjacent to the functionally-localized area V6 and dorsal to the retinotopic area V3A. On average, when localized at the same threshold level (p<0.05), pIPG was approximately 57% smaller than area RSC. Despite its small size, pIPG was detected robustly across different scan sessions (conducted on different days) and showed a stronger response to different scenes compared to faces and/or intact objects. Interestingly, and in contrast to other scene-selective areas that remain insensitive to the coherency of scenes when presented sequentially, pIPG showed a significantly stronger response to coherent (compared to incoherent) sequence of scenes that implied ego-motion. Further tests suggested that this effect is, at least partly, due to the significant sensitivity of pIPG response to optic flow (p<0.05), especially when presented within the peripheral visual field. Our findings suggest that scene perception in dynamic environments, and cognitive tasks that rely on it (e.g. navigation and ego-motion control), rely on a network of fine-scale scene-selective sites, beyond the previously-known areas PPA, RSC, and TOS.