Abstract
While over two decades of research has investigated the neural mechanisms underlying human visual place or “scene” processing, a fundamental question remains unanswered: What exactly is a scene? Intuitively, we are always inside a scene (while interacting with the outside of objects); hence, one intrinsic property of a scene may be concavity. Here, using two functional magnetic resonance imaging (fMRI) studies in humans, we directly tested the strongest predictions of this hypothesis: 1) if a scene-selective region tracks the concavity of a scene, then it will be sensitive to changes in concavity but not convexity of spatial boundary cues, and 2) if concavity is a diagnostic property of a scene, then a scene-selective region will respond not only to images of scenes, but also to non-scene images that depict concavity, such as the inside of objects. Consistent with our predictions, we found that a scene-selective cortical region (the parahippocampal place area, PPA) shows an increasing response to images of spatial boundary cues parametrically changing in concavity but not convexity, and to the inside of objects over the outside of objects. By contrast, an object-selective region (the lateral occipital complex, LOC) shows a greater response to convexity than concavity, and to the outside of buildings over the inside of buildings. Taken together, these results provide converging evidence that concavity is an intrinsic property of a scene, and raise the intriguing hypothesis that concavity versus convexity may be a diagnostic visual feature enabling the human brain to differentiate scenes from objects.
Acknowledgement: Emory College, Emory University (DDD), National Eye Institute grant R01EY026042 (SJP)