Figure 1. .

Relative overrepresentation ϱ of bidirectional connections in networks with a fraction of pairs connected with a high probability x and the rest of the pairs connected with a low probability y. (A) Diagram illustrating the targets with a high chance x of connecting (thick arrows) and targets with a low probability y of connecting (thin arrows) for a single source node (hatched). (B) Different pairings of x and y can induce a high relative overrepresentation ϱ in a network with two-point-distributed connection probabilities, $P_{ij}\sim \mathcal{T}(\frac{\mu -y}{x-y},x,y)$, and a fixed overall connection probability μ = 0.1. The dashed line marks an overrepresentation of bidirectional connections of ϱ = 4, observed for Layer 5 pyramidal neurons in rat visual cortex (Song et al., 2005).