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- P. Adorjan, P. Buzas,
Z. Kisvarday, U. Eysel, and K. Obermayer. Orientation Specificity of
Excitatory and Inhibitory Connections in Cat Visual Cortex: Statistical
Analysis.
.
In European J. Neurosci., volume 10, page 234. European Forum of
Neuroscience ENA, 1998.
We analysed the distribution of synaptic terminals of pyramidal
(n=2) and basket cells (n=2) aligned with the corresponding orientation maps
obtained with optical imaging. We asked whether the orientation specifity of
the connections can be explained by (i) the geometrical pattern of the
orientation map or by (ii) a general structure of the axonal trees.
Addressing the first question we found that, at most distances beyond 200um,
the cells have significantly (p<0.001) more specific connections than
that would follow from an angularly homogenous terminal distribution.
Pyramidal terminals are strongly biased to iso- and oblique orientations. Of
the two basket cells, one showed specificity for iso- and cross-orientations
while the other one for oblique orientations. The question arises whether a
general template for the axonal morphology could account for the
specific connections. By shifting the axonal trees to random positions
significant specifity remains for one of the pyramidal cells only at
hypercolumn distances from the soma. In the case of the other pyramid and of
the basket cells the specifity diminishes against the angularly homogenous
distributions. We conclude that the specifity of the excitatory and
inhibitory connections can neither be completely explained by the topography
of the orientation map nor it is a sole consequence of the axonal structure.
As a natural prediction it follows that the developement of lateral
connection patterns involves dynamic pattern formation.
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