Intrinsic connections in tree shrew V1
Vision Research, Volume 44, Issue 9, Pages 857-876, April 2004
imply a global to local mapping
David M. Alexandera,f,
Paul D. Bourkeb,
James J. Wrighte,f.
Brain Dynamics Centre, Acacia House, Westmead Hospital, Hawkesbury Road, Westmead 2145,
Centre for Astrophysics and Supercomputing, Swinburne University of Technology,
523 Burwood Road, Hawthorn 3122, Melbourne, Australia
School of Computing and Information Technology, Griffith University,
University Drive, Meadowbrook 4131, Brisbane, Australia
School of Mathematics and Statistics, University of Sydney, City Road, Glebe 2006,
The Liggins Institute, University of Auckland, 2-6 Park Avenue, Grafton 1001, Auckland,
Brain Dynamics Laboratory, Mental Health Research Institute ofVictoria, 155 Oak Street,
Parkville 3052, Melbourne, Australia
The local-global map hypothesis states that locally organized response properties ---
such as orientation preference --- result from
visuotopically organized local maps of non-retinotopic response properties.
In the tree shrew, the lateral extent of horizontal patchy
connections is as much as 80-100% of V1 and is consistent with the length
summation property. We argue that neural signals can be
transmitted across the entire extent of V1 and this allows the formation of maps at the
local scale that are visuotopically organized.
We describe mechanisms relevant to the formation of local maps and report modelling
results showing the same patterns of horizontal
connectivity, and relationships to orientation preference, seen in vivo. The
structure of the connectivity that emerges in the
simulations reveals a "hub and spoke" organization.
Singularities form the centers of local maps, and linear zones and saddle-points
arise as smooth border transitions between maps. These findings are used to
present the case for the local-global map hypothesis for tree shrew V1.