Abstract
Space-related processing recruits a network of brain regions separate from those recruited in object-related processing. This dissociation has largely been explored using views of navigable-scale spaces compared to singleton objects. However, in naturalistic visual experience, we encounter spaces intermediate to these extremes, like the tops of desks and kitchen counters, which are not navigable but typically contain multiple objects. How are such intermediate “reachspaces” represented in the brain? Human participants underwent functional neuroimaging in which brain responses to reachspaces were compared with responses to scene and object views (Experiment 1, N=12). We found evidence for at least two regions that prefer reachspaces to both scenes and objects: one in ventral visual cortex (11/12 participants), one in occipito-parietal cortex (10/12 participants), with a potential third region in superior parietal cortex. Reachspace preferences were maintained in these regions even when all images were equalized in luminance, contrast and spatial frequency (Experiment 2a, N=12), indicating that low-level differences alone cannot account for these activation differences. Furthermore, these regions respond more strongly to views of multiple objects on blank backgrounds than to empty near-scale spaces (Experiment 2b), pointing to a role for multi-object processing. Finally, reachspaces elicited activity in both scene- and object-selective ROIs, driving each of these regions to an intermediate degree. Taken together, these results provide evidence for a neural distinction between reachspaces, full-scale scenes, and singleton object views. Broadly, the current evidence suggests that visual representations of reachable environments may draw on object-based and space- based computations, as well as recruiting additional regions to support multi-object processing.
Acknowledgement: Star Family Challenge Grant to TK, NIH Shared Instrumentation Grant S10OD020039