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- P. Wiesing and
K. Obermayer. Lateral Competition: the interplay of Inhibition and
Excitation in Primary Visual Cortex on the Development of Topographic
Projections and Ocular Dominance Maps.
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In Proceedings of the 29th Göttingen Neurobiology Conference,
page 631, 2003.
The development of visual cortex feature maps, e.g. ocular
dominance maps, topographic maps and orientation maps, have been extensively
investigated and numerous modeling studies have examined their development.
Two prevalent classes of Hebbian models are correlation based learning models
(CBL) and self-organizing maps (SOM), which have both been proposed to
explain the activity driven formation of cortical maps. Both models differ
significantly in the way lateral cortical interactions are treated leading to
different predictions for the formation of receptive fields. In previous
studies (Piepenbrock and Obermayer, 2000, Wiesing and Obermayer, 2001) we
investigated a class of models which are characterized by a variable degree
of lateral competition and which have the CBL and SOM models as limit cases.
We showed that there exists a critical value for intracortical competition
below which the model exhibits correlation based learning properties and
above which feature mapping sets in. This mechanism of variable degree of
competition, formulated through a softmax-function, allows analytical
predictions, but due to his mathematical formalization do not find its direct
equivalent in biology. Using a firingrate-based mean field model (Bartsch et
al. 2000) we examine the development of afferent synaptic weights between two
input layers (left/right LGN ON cells) and one cortical layer of neurons (V1
input layer, one excitatory and one inhibitory cell population) in a more
biological realistic way. We motivate each used parameter in detail and show
in which parameter regimes localized receptive fields and ocular dominance
bands will form.
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