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- J. M. Young, W. J. Waleszczyk,
C. Wang, M. B. Calford, K. Obermayer, and B. Dreher. The spike
timing-dependent influence of intrinsic long-range connectivity over
post-natal topographic organization in primary visual cortex.
.
In Computational and Systems Neuroscience, 2008.
For over two decades, models applied to the problem of topographic
map development in sensory cortex have assumed that intrinsic long-range
connectivity plays an important role in the activity-dependent refinement of
these maps [1-3]. However, there is a large body of experimental evidence
demonstrating that input provided via these connections is predominantly
subthreshold (or only weakly suppressive), and therefore unlikely to be able
to significantly influence an activity-dependent process of this kind. The
objective of this study was to determine whether, during early postnatal
development, activity propagated by long-range horizontal cortical
connections can induce long-term changes in the location of a neuron's
classical receptive field. We investigated this issue by looking for
receptive field location changes among neurons in cat primary visual cortex
that had their intrinsic horizontal input chronically altered by the presence
of a neighboring zone of partial feedforward input loss (created by a
monocular retinal lesion made at 8 weeks postnatal). Despite receiving normal
feedforward input, these neurons outside the deafferented zone underwent
extensive changes in the location of their classical receptive fields.
Neurons inside the deafferented zone also shifted the locations of their
receptive fields, and we have previously demonstrated [4] that these shifts
are consistent with changes in horizontal connectivity (catalyzed by
increases in neuronal gain) that are spike timing-dependent and inconsistent
with changes that are spike correlation-dependent. Here we applied the same
model to reorganization outside the deafferented zone, and a comparison of
the simulated and in vivo receptive field shifts reveals that the same
plasticity principles underlie the connectivity changes in this region also.
Our results indicate that intrinsic horizontal cortical connections, via
spike timing-dependent plasticity, do indeed have the capacity to exert a
powerful influence on receptive field location, but this capacity is kept
under strict control via a close coupling of the excitation and inhibition
elicited by horizontal input. Our results, therefore, support the fundamental
assumption of topographic map development models that intrinsic long-range
cortical connectivity has the capacity to shape long-term changes in neuronal
receptive field location.
References:
1. Kohonen, T., Self-organized
formation of topologically correct feature maps. Biological Cybernetics,
1982. 43: p. 59-.
2. Obermayer, K., H. Ritter, and K. Schulten, A
Principle for the Formation of the Spatial Structure of Cortical Feature
Maps. Proceedings of the National Academy of Sciences of the United States of
America, 1990. 87(21): p. 8345-8349.
3. Song, S. and L.F. Abbott,
Cortical development and remapping through spike timing-dependent plasticity.
Neuron, 2001. 32(2): p. 339-50.
4. Young, J.M., et al., Cortical
reorganization consistent with spike timing- but not correlation- dependent
plasticity. Nature Neuroscience, 2007. 10(7): p. 887-895.
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