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Arash Yazdanbakhsh, Oliver Layton; Multi-scale selectivity to figures in primate V4. Journal of Vision 2013;13(9):711. doi: 10.1167/13.9.711.
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© ARVO (1962-2015); The Authors (2016-present)
Neurons in primate V4 have been shown to respond to curved contours and local convexities/concavities (Pasupathy & Connor 1999). Evidence indicates that V4 neurons do not passively integrate contrast, but rather their response depends on figure-ground segregation. When the receptive field is centered on the edge of a figure, substantial numbers of V4 neurons elicit a selective response, depending on which side the figure is located (border-ownership) (Zhou et al. 2000). V4 neurons demonstrate response suppression when shapes to which they are selective are occluded by another (Bushnell et al. 2011), respond to shapes when they appear at a variety of sizes, and have a spectrum of receptive fields sizes that grow at peripheral eccentricities (Piñon et al. 1998). How do V4 cells achieve their selectivity to multiple shapes at different spatial scales and suppress responses outside of figures? We introduce a model of primate V4 in which neural units with a range of receptive field sizes and scatter at proximal visuotopic positions compete to suppress responses outside of figures. To account for the high degree of variance in V4 cell selectivity (Hegdé & van Essen 2006), we sample model V4 receptive field shapes from the Zernike polynomial basis, which is capable of fitting all geometrical patterns observed in V4. In the model, competitive interactions across scale and space generate activity peaks for scales and locations at which figures likely appear in the visual scene. Another layer of units groups the resultant activity from spatially-offset V4 subpopulations and elicits responses inside of figures in the visual scene. Results show that the exterior of figures tends to elicit uniform activity across units with different receptive field sizes and those units are suppressed through competition. Model results elucidate the importance of convexity and closure in figure-ground segregation.
Meeting abstract presented at VSS 2013
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