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Samoni Nag, Daniel Berman, Julie Golomb; Depth sensitivity of category-selective visual areas to preferred and non-preferred stimuli. Journal of Vision 2018;18(10):401. doi: 10.1167/18.10.401.
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To make sense of our 3D environment, our brains must transform 2D visual inputs into 3D representations that contain depth information. In human visual cortex, the representation of depth information gradually increases from low- to mid- to higher-level brain regions (Finlayson et al., 2017). Along this hierarchy are category-selective regions (e.g., FFA, LOC, PPA, OPA) that are tuned to a select set of preferred-stimuli (e.g., faces, objects, scenes). An open question is whether these category-selective regions of interest (ROIs) exhibit depth sensitivity in addition to processing their preferred-stimulus categories. In a blocked fMRI experiment, subjects wore red/green anaglyph glasses and viewed a series of category-specific (i.e., faces, objects, scenes) and unspecific (i.e., moving dots) stimuli. Critically, these stimuli were presented at different depths such that they appeared in front of, behind, or at the same depth plane as the fixation point. Comparisons of overall ROI activation between back, middle, and front depths reveal that FFA and LOC may exhibit a front preference whereas scene-selective PPA and OPA exhibit general depth sensitivity (i.e., both back and front > middle). Additionally, motion cortex (MT) exhibits a strong front > middle > back depth preference. This pattern of results might reflect the notion that faces and objects typically appear at near-depths while scenes span both near- and far-depths. A more intriguing question asks whether these ROIs exhibit specific depth preferences for their preferred-stimulus categories. We compared activation in these ROIs across different combinations of depth and stimulus type. Preliminary results suggest that FFA exhibits a stronger front preference for its preferred-stimulus (faces), though it remains unclear whether other ROIs exhibit a specific preference for their preferred-stimuli. These findings shed light on how category-selective areas of cortex incorporate and process depth information.
Meeting abstract presented at VSS 2018
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