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Assaf Harel, Jeffrey Nador, Michael Bonner, Russell Epstein; Early electrophysiological markers of navigational affordances in scenes. Journal of Vision 2018;18(10):733. doi: 10.1167/18.10.733.
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Recent work has demonstrated that information about the structure and function of visual scenes is encoded in the brain by 220ms post-stimulus onset. For example, Harel et al. (2016) reported that diagnostic scene properties, such as spatial expanse (open vs. closed) and naturalness (manmade vs. naturalness), modulate the amplitude of early visual Event-Related Potentials (ERPs), particularly the P2. Given that open and closed scenes can be thought as two ends on a navigability continuum, we reasoned that these ERP markers might contain information about the number of pathways that afford movement in the local environment. To test this idea, we recorded ERPs from participants while they passively viewed computer-generated room scenes matched in visual complexity used in a previous fMRI study of navigability (Bonner & Epstein, 2017). By simply changing the number of doors (no-doors, one door, two doors, three doors) we were able to systematically control the number of movement paths in the scene, while keeping the overall size and shape of the environment constant. We found that rooms with no doors evoked a higher P2 response than rooms with three doors, analogous to the higher P2 amplitude to closed relative to open scenes previously reported. The P2 amplitude to rooms with one or two doors was higher than three-door rooms but lower than the response to no-door rooms. The parametric navigability effect on the ERP waveforms persisted following the P2 peak (around 250ms), lasting up until 650ms post-stimulus onset. Together, these results suggest that the perceived ease of navigation in a scene, as reflected by the number of potential pathways through it, is represented in both early and late stages of scene perception. This finding complements recent fMRI research showing that the occipital place area automatically encodes the structure of navigable space in visual scenes.
Meeting abstract presented at VSS 2018
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