The Journal of Neuroscience, February 1, 2000, 20(3):1119-1128
Structured Long-Range Connections Can Provide a Scaffold for
Orientation Maps
Harel Z.
Shouval1,
David H.
Goldberg1,
Judson
P.
Jones2,
Martin
Beckerman2, and
Leon N.
Cooper1
1 Departments of Neuroscience and Physics and the
Institute for Brain and Neural Systems, Brown University, Providence,
Rhode Island 02912, and 2 Computer Science and Mathematics
Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
In the visual cortex of the cat and ferret, it is established that
maturation of orientation selectivity is shaped by experience-dependent plasticity. However, recent experiments indicate that orientation maps
are remarkably stable and experience-independent. We present a model to
account for these seemingly paradoxical results. In this model, a
scaffold consisting of non-isotropic lateral connections is laid down
in horizontal circuitry before visual experience. These lateral
connections provide an experience-independent framework for the
developing orientation maps by inducing a broad orientation tuning bias
in the model neurons. Experience-dependent plasticity of the
thalamocortical connections sharpens the tuning while the preferred
orientation of the neurons remains unchanged. This model is verified by
computer simulations in which the scaffolds are generated both
artificially and inferred from experimental optical imaging data. The
plasticity is modeled by the BCM synaptic plasticity rule, and the
input environment consists of natural images. We use this model to
provide a possible explanation of the recent observation in which two
eyes without common visual experience develop similar orientation maps.
Finally, we propose an experiment involving the disruption of lateral
connections to distinguish this model from models proposed by others.
Key words:
orientation map; synaptic plasticity; visual cortex; model; lateral connections; natural images
Copyright © 2000 Society for Neuroscience 0270-6474/00/2031119-10$05.00/0
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