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- P. Adorjan, J. B. Levitt,
J. S. Lund, and K. Obermayer. A Model for the Intracortical Origin of
Orientation Preference and Tuning in Macaque Striate Cortex.
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Visual Neurosci., 16:303-318, 1999.
(FTP Gzipped PostScript, 34 pages, 274 kb)
We report results of numerical simulations for a model of
generation of orientation selectivity in macaque striate cortex. In contrast
to previous models, where the initial orientation bias is generated by
convergent geniculate input to simple cells and subsequently sharpened by
lateral circuits, our approach is based on anisotropic intracortical
excitatory connections which provide both the initial orientation bias and
its subsequent amplification. Our study shows that the emerging response
properties are similar to the response properties that are observed
experimentally, hence the hypothesis of an intracortical generation of
orientation bias is a sensible alternative to the notion of an afferent bias
by convergent geniculocortical projection patterns. In contrast to models
based on an afferent orientation bias, however, the amp;quot;intracortical
hypothesisamp;quot; predicts that orientation tuning gradually evolves from
an initially nonoriented response and a complete loss of orientation tuning
when the recurrent excitation is blocked, but new experiments must be
designed to unambiguously decide between both hypotheses.
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