Sequential bifurcation of orientation { and ocular dominance

In the visual cortex of mammals, information is processed by an array of columnar modules. The layout of these columns constitutes a complex spatial pattern, which is supposed to arise due to Hebb{type self{organization during early life. The layout of columnar patterns diiers strongly among species. Here we show that timing and dynamic rearrangement due to Hebb{type self{organization explains the diierent appearance of ocular dominance and orientation columns in cat and monkey striate cortex. In particular, we demonstrate that the reenement of intracortical and aaerent connections during development triggers a series of bifurcations, in which diierent columnar systems emerge in a sequence proceeding from larger to smaller spatial length scales. Numerical simulations show that these predicted diierences in timing of cortical pattern formation result in diierent spatial layouts, that are in excellent agreement with experimental observations.