Perceptual sensitivity maps within globally defined visual shapes

AN unsolved problem of biology is the processing of global shape in natural vision. The known processes of early vision are spatially restricted (or local) operations, and little is known about their interactions in organizing the visual image into functionally coherent (or global) objects. Here we introduce a human psychophysical method which allows us to measure the effect of perceptual organization on the activity pattern of local visual detectors. We map differential contrast sensitivity for a target across regions enclosed by a boundary. We show that local contrast sensitivity is enhanced within the boundary even for large distances between the boundary and the target. Furthermore, the locations of maximal sensitivity enhancement in the sensitivity maps are determined by global shape properties. Our data support a class of models which describe shapes by the means of a medial axis transformation1–3, implying that the visual system extracts ‘skeletons’ as an intermediate-level representation of objects. The skeletal representation offers a structurally simplified shape description which can be used for higher-level operations and for coding into memory.

[1]  H. Blum.  A New Model of Global Brain Function , 2015, Perspectives in biology and medicine.

[2]  R. Brubaker.  Models for the perception of speech and visual form: Weiant Wathen-Dunn, ed.: Cambridge, Mass., The M.I.T. Press, I–X, 470 pages , 1968 .

[3]  H. Blum.  Biological shape and visual science (part I) , 1973 .

[4]  D. Tolhurst,et al.  Interactions between spatial frequency channels , 1978, Vision Research.

[5]  HARRY BLUM,et al.  Shape description using weighted symmetric axis features , 1978, Pattern Recognit..

[6]  S Marcelja,et al.  Mathematical description of the responses of simple cortical cells. , 1980, Journal of the Optical Society of America.

[7]  U. Polat,et al.  Lateral interactions between spatial channels: Suppression and facilitation revealed by lateral masking experiments , 1993, Vision Research.

[8]  David J. Field,et al.  Contour integration by the human visual system: Evidence for a local “association field” , 1993, Vision Research.

[9]  I Kovács,et al.  A closed curve is much more than an incomplete one: effect of closure in figure-ground segmentation. , 1993, Proceedings of the National Academy of Sciences of the United States of America.

[10]  R. Frostig,et al.  Cortical point-spread function and long-range lateral interactions revealed by real-time optical imaging of macaque monkey primary visual cortex , 1994, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[11]  U. Polat,et al.  The architecture of perceptual spatial interactions , 1994, Vision Research.