Structure and parameters of the model.

<p><b>A</b>, Our NC model is schematically illustrated. The connection probability is higher in clusters (<i>c</i>₂) than outside (<i>c</i>₁). Connections inside and outside clusters are shown in red and blue, respectively. <b>B</b>, The parameter sets predicted by the model are depicted on the plane of <i>α</i> and <i>β</i> with filled circles. The numbers near the circles correspond to the values of <i>K</i>. Empty circles depict the sets obtained under the assumption of 10% connections loss in slice preparations. <b>C</b>, The experimentally observed threshold-dependence of the overrepresentation of reciprocal connections is fitted by models for different values of <i>K</i>. The best fit with <i>K</i> = 1 is red, the first after best fit with <i>K</i> = 2 is blue, the other fits are black. The number near each data point shows the number of the corresponding connections obtained by experiment. <b>D</b>, The probability densities of synaptic weights are shown for <i>K</i> = 1: <i>f</i>₂(<i>w</i>) stands for connections inside the cluster and <i>f</i>₁(<i>w</i>) for all the other connections, and <i>f</i>(<i>w</i>) for all connections in the entire network. The two distributions have identical values, i.e., <i>f</i>₁(<i>w</i>₀) = <i>f</i>₂(<i>w</i>₀), at the threshold value of <i>w</i>₀ = 1.12 [mV].