Can V1 Mechanisms Account for
Figure-Ground and Medial Axis Effects?
Gatsby Computational Neuroscience Unit
University College London
In Advances in Neural Information Processing Systems 12 MIT
Press, Cambridge, MA, 2000.
When a visual image consists of a figure against a background, V1 cells
are physiologically observed to give higher responses to image regions corresponding to
the figure relative to their responses to the background. The medial axis of the figure
also induces relatively higher responses compared to responses to other locations in the
figure (except for the boundary between the figure and the background). Since the
receptive fields of V1 cells are very small compared with the global scale of the
figure-ground and medial axis effects, it has been suggested that these effects may be
caused by feedback from higher visual areas. I show how these effects can be accounted for
by V1 mechanisms when the size of the figure is small or is of a certain scale. They are a
manifestation of the processes of pre-attentive segmentation which detect and highlight
the boundaries between homogeneous image regions.
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