at website: http://www.gatsby.ucl.ac.uk/~zhaoping/preattentivevision.html
This paper is to be published in SPATIAL VISION, 1999
Title: Pre-attentive segmentation in the primary visual cortex
Author: Zhaoping Li
Abstract: The activities of neurons in primary visual cortex have been
shown to be significantly influenced by stimuli outside their classical
receptive fields. We propose that these contextual influences serve
pre-attentive visual segmentation by causing relatively higher
neural responses to important or conspicuous image locations,
making them more salient for perceptual pop-out. These locations
include boundaries between regions, smooth contours, and pop-out
targets against backgrounds. The mark of these locations is the
breakdown of spatial homogeneity in the input, for instance, at the
border between two texture regions of equal mean luminance. This
breakdown causes changes in contextual influences, often resulting
in higher responses at the border than at surrounding locations.
This proposal is implemented in a biologically based model of V1 in
which contextual influences are mediated by intra-cortical
horizontal connections. The behavior of the model is demonstrated
using examples of texture segmentation, figure-ground segregation,
target-distractor asymmetry, and contour enhancement, and is
compared with psychophysical and physiological data. The model
predicts (1) how neural responses should be tuned to the orientation
of nearby texture borders, (2) a set of qualitative constraints
on the structure of the intracortical connections, and (3) stimulus
dependent biases in estimating the locations of the region borders by
pre-attentive vision.