article on LATERAL INTERACTIONS

[M.Usher@ukc.ac.uk]

The following article, to appear in SPATIAL VISION
(Special Issue on "Long Range Spatial Interactions in Vision"),
can now be accessed from:
http://ukc.ac.uk/psychology/people/usherm/ (at recent  publications)

The article addresses psychophysical data that indicate facilitatory
lateral interaction in visual processing, and presents a computational
model based on principles from neural information processing and signal
detection theory, to explain those interactions.

-Marius Usher

Department of Psychology
University of Kent

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     MECHANISMS FOR SPATIAL INTEGRATION IN VISUAL DETECTION:
        A model based on lateral interactions

    Marius Usher, Yoram Bonneh, Dov Sagi & Michael Herrmann

                   Abstract

Studies of visual detection of multiple targets  show a weak
improvement of thresholds with the number of targets, which
corresponds to a fourth-root power law. We find this result to 
be inconsistent with probability summation models, and account
for it by a model of ``physiological'' integration that is based 
on excitatory lateral interactions in the visual cortex.
The model explains several phenomena which are confirmed by the
experimental data, such as the absence of spatial and temporal
uncertainty effects, temporal summation curves, and facilitation
by a pedestal in 2AFC tasks. The summation exponents are dependent 
on the strength of the lateral interactions, and on the distance 
and orientation relationship between the elements.