Abstract
The ability to navigate through various environments is crucial for all mobile organisms. Recent body of work has suggested that the occipital place area (OPA) encodes information crucial for spatial navigation, especially by utilizing boundaries (i.e. walls) which define the spatial structure of a scene. However, little is known about the role of objects, which might change the navigability by obstructing the possible path. Here, we tested whether the OPA and other scene-selective regions (PPA, RSC) encode the presence of an obstacle. During fMRI scan, participants performed one-back repetition detection task while being presented with outdoor/open space images with an object (e.g. a rock) and a visible path shown on the ground. Four different conditions were created as a combination of path direction (to the Left vs. Right), and object location (on the Left vs. Right). The object served as an obstacle blocking the navigable path only when path direction and object location matched. By analyzing multi-voxel patterns in scene-selective regions using SVM classifiers (preliminary data, N=7), we found significant above-chance classification in the OPA for path direction, object location, and importantly, for obstacle presence. The current study is the first to demonstrate that the OPA encodes the existence of an object hindering the passage, namely obstacle . This result is striking in a sense that it signifies similar coding in OPA for the two exact opposite conditions (i.e. treating left-left and right-right path direction-object location pairs alike as “obstacle present”). Furthermore, the coding of non-surface navigational barrier in the outdoor/open space signifies that the OPA supports navigation even when no wall-like boundaries are present. Together, these results serve as an evidence that the OPA encodes the existence of obstacle through merged representation of path direction and object location, indicating its role beyond boundary-based navigation.