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Models of Neural Systems

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On the Influence of Threshold Variability in a Model of the Visual Cortex
Citation key Bartsch1999
Author Bartsch, H. and Stetter, M. and Obermayer, K.
Title of Book Artificial Neural Networks - ICANN 99
Pages 73 – 78
Year 1999
ISBN 0-85296-721-7
ISSN 0537-9989
DOI 10.1049/cp:19991087
Volume 1
Publisher IEEE
Abstract Orientation–selective neurons in monkeys and cats show contrast saturation and contrast–invariant orientation tuning \\citealbr82. Recently proposed models for orientation selectivity predict contrast invariant orientation tuning but no contrast saturation at high strength of recurrent intracortical coupling, whereas at lower coupling strengths the contrast response saturates but the tuning widths are contrast dependent \\citehans97,bart97. In the present work we address the question, if and under which conditions the incorporation of a stochastic distribution of activation thresholds of cortical neurons leads to the saturation of the contrast response curve as a network effect. We find that contrast saturation occurs naturally if two different classes of inhibitory inter-neurons are combined. Low threshold inhibition keeps the gain of the cortical amplification finite, whereas high threshold inhibition causes contrast saturation.
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