Dissociating object and space representations in scene-selective visual cortex

Abstract

Neuroimaging studies have identified a network of scene-selective cortical regions: Parahippocampal Place Area (PPA), Retrosplenial Complex (RSC) and Transverse Occipital Sulcus (TOS). However, the different contributions of these areas to scene recognition are unclear. Further, while PPA shows a stronger response to scenes than objects it also contains significant object information. To reconcile these findings and elucidate the nature of scene processing in each region, we assessed the relative impact of objects and spatial backgrounds on responses. We manipulated object and spatial information by generating minimal scenes comprising one of seven objects (or no object), presented on one of three different backgrounds differing in the spatial information they contain (room interior, horizon, and luminance gradient). The horizon and room backgrounds conveyed depth information, but only the room defined an enclosed space. Unlike other studies using real-world, but visually uncontrolled scenes, these minimal scenes provide a simple controlled test of the relative contribution of objects and backgrounds. Individual scenes were presented in an ungrouped event-related fMRI experiment and the distributed response patterns to each were analyzed using split-half correlations. Response patterns in scene-selective cortex discriminated both objects and backgrounds. However, different scene-selective regions emphasized different aspects of the scenes. RSC primarily reflected the spatial aspects of the scenes, discriminating backgrounds regardless of objects and showing no modulation of response strength by object presence. In contrast, PPA and TOS responded more strongly in the presence of an object and showed strong discrimination of objects as well as backgrounds. However, object discrimination in PPA, but not TOS, was modulated by the type of background, with the strongest discrimination against room backgrounds. We conclude that while RSC mainly represents spatial information, PPA and TOS represent both object and spatial information to provide a rich representation of the visual environment.