@Article{tal1997:topological,
  author =       {Tal, D. and Schwartz, E. L.},
  title =        {Topological singularities in cortical orientation
                  maps: the sign theorem correctly predicts
                  orientation column patterns in primate striate
                  cortex},
  journal =      {Network: Computation in Neural Systems},
  volume =       8,
  number =       2,
  pages =        {229--238},
  month =        may,
  year =         1997,
  datestr =      199705,
  INSPEC =       5607510,
  abstract =     {This work indicates that primate visual cortex
                  orientation column structure is best understood in
                  the context of other `ordered continuous media'
                  (e.g. liquid $He^3$, cholesteric liquid crystals,
                  random optical phase maps, to name only a few) in
                  which an order parameter (orientation in this case)
                  is mapped to a physical space, and in which the
                  topological properties of the mapping determine the
                  observable regularities of the system. We also point
                  out that these methods may well be applied to a
                  variety of other cortical map systems which admit an
                  `order parameter', i,e. for which each cortical
                  position is assigned a continuous stimulus value},
}