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 “intracortical
hypothesis” 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.