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2000 Nature America Inc. http://neurosci.nature.comarticlesA mapping label required for
normal scale of body
representation in the cortexPierre Vanderhaeghen1,2, Qiang Lu1, Neal Prakash3, Jonas Frisn4, Christopher A. Walsh5, Ron D.
Frostig3 and John G. Flanagan1.com1 Department of Cell Biology and Program in Neuroscience, Harvard Medical School, Boston, Massachusetts 02115, USA2 Present address: Institute of Interdisciplinary Research, University of Brussels, B-1070 Brussels, Belgium3 Department of Neurobiology and Behavior and Center for the Neurobiology of Learning and Memory, University of California at Irvine,
Irvine, California 92697, USA4 Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institute, S-171 77 Stockholm, Sweden5 Division of Neurogenetics, Department of Neurology, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02115, USAThe first two authors contributed equally to this work.Correspondence should be addressed to J.G.F. ([email protected]) http://neur
osci.nature2000 Nature America Inc.The neocortical primary somatosensory area (S1) consists of a map of the body surface. The cortical
area devoted to different regions, such as parts of the face or hands, reflects their functional
importance. Here we investigated the role of genetically determined positional labels in neocortical
mapping. Ephrin-A5 was expressed in a medial > lateral gradient across S1, whereas its receptor EphA4
was in a matching gradient across the thalamic ventrobasal (VB) complex, which provides S1 input.
Ephrin-A5 had topographically specific effects on VB axon guidance in vitro. Ephrin-A5 gene disruption
caused graded, topographically specific distortion in the S1 body map, with medial regions contracted
and lateral regions expanded, changing relative areas up to 50% in developing and adult mice. These
results provide evidence for within-area thalamocortical mapping labels and show that a genetic difference can cause a lasting change in relative scale of different regions within a topographic map.The layout of the neocortical surface reflects its functions. For
example, the primary somatosensory area (S1) consists of a topographic map of the body surface, in which different parts of the
body are represented at different scales1,2. The scale of such features varies between species, and even individuals, in a manner
that reflects functional importance and probably contributes to
differences in functional ability18.Such topographic organization requires corresponding patterning of incoming and outgoing connections. One mechanism
for topographic patterning of connections is correlated neural
activity. In visual cortex, neural activity and visual experience are
important for...