Overlap among dendrites in neuronal networks is a designed entity onto which functional topology is coded

Information processing in the brain is performed by propagating data through an array of neuronal networks, each having unique structural and topological architectures. However, the mechanisms that specify these architectures are not well understood. We found that neuronal networks in vitro determine the pattern and strength of their connectivity by designing the way dendrites overlap. The branches of neighboring dendrites converge in a collective and ordered fashion, leading to a network configuration that enables axons to innervate multiple and remote dendrites using short wiring lengths. In addition, the convergence sites are associated with synaptic clusters of higher density and strength than found elsewhere, leading to patchy distribution of synaptic strength in the network. Thus, controlled design of the overlap among dendrites patterns and strengthens neuronal connectivity in neuronal networks.