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Bria Long, Talia Konkle; Mid-level features are sufficient to drive the animacy and object size organization of the ventral stream. Journal of Vision 2017;17(10):575. doi: 10.1167/17.10.575.
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The ventral visual stream exhibits a large-scale organization by the dimensions of animacy and real-world size (Konkle & Caramazza, 2013). While this organization could reflect a conceptual-level distinction, there are also perceptual differences between animals, big objects, and small objects, evidenced by systematic mid-level feature differences (Long et al., 2016). Here, we examined whether these mid-level feature differences are sufficient to drive the ventral stream organization by animacy and object size. Using a customized texture synthesis model, we created a stimulus set from images of big animals, big objects, small animals, and small objects. These stimuli preserve mid-level information about texture and form ("texforms"), but are unrecognizable at the basic-level. Eight observers underwent functional neuroimaging while viewing texform images and the original counterparts. For each voxel in the ventral stream, we computed animacy preferences (animals – objects) and real-world size preferences (small objects – big objects), for both original and texforms images. These preference maps were correlated with each other to assess the similarity of the animacy and real-world size topographies. Overall, we found that texforms elicited robust animacy and size preference maps across the entire ventral stream. Further, these maps exhibited a highly similar spatial topography to the maps generated when observers viewed recognizable images (Animacy: r=.76, t(7)=22.3, p< 0.001; Size: r=.43, t(7)=5.7, p< 0.001). In a replication experiment, we presented images above and below fixation, and again found that texforms and original images generated similar topographies (Animacy: r=.69, t(7)=9.8, p< 0.001; Size: r=.36, t(7)=5.4, p=0.001). These results demonstrate that the ventral stream organization does not rely on intact basic-level recognition, and that mid-level feature differences drive ventral visual cortex in a way that is not simply inherited from retinotopy. Broadly, these data imply that mid-level perceptual information is represented along the ventral stream well beyond early visual areas.
Meeting abstract presented at VSS 2017
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