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Yoonjung Lee, Soojin Park; Representation of scene navigability and structure in two distinct cortical pathways. Journal of Vision 2019;19(10):162a. doi: https://doi.org/10.1167/19.10.162a.
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Two distinct cortical pathways have been identified in monkeys and humans for visual processing—dorsal and ventral pathways. Previous studies have identified regions specified for processing visual scene information, one in a dorsal pathway, the Occipital Place Area (OPA) and another in a ventral pathway, the Parahippocampal Place Area (PPA). Here, we examined how neural representation of navigability in scenes arises along the brain regions in two different visual pathways, leading to the two scene-specific regions. We defined the regions extending from the primary visual cortex (V1) through the OPA as a dorsal stream, while those extending from V1 through the PPA as a ventral stream. During fMRI scans, participants (N=14) performed a one-back task while viewing natural outdoor scenes in a blocked design. The scenes were defined by the difference in level of navigability (more-navigable vs. less-navigable) and its global structural property (open vs. closed). Using Representational Similarity Analyses, we discovered that the neural RDMs in the regions of dorsal stream (V3, V3A and the OPA) and the PPA of ventral stream are highly correlated (Kendall’s tau-a) with the model RDM of navigability than the model RDM of structure. For the neural RDMs in the regions of ventral stream (V1, ventral V2, VP and V4), we found higher correlation with the structure model than the navigability model. These results suggest differential contribution of the dorsal and the ventral stream in representing the navigability and structure of scenes. Importantly, navigability decoding index, computed by subtracting correlation coefficients of structure model from those of navigability model for each individual, was only significant for the OPA. These results suggest that OPA in the dorsal stream is at the apex of representing navigability in scenes, supporting a rapid computation of navigational affordance in visual scenes.
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