Activity-dependent plasticity refers to a range of mechanisms for adaptively reshaping neuronal connections. We model their common principle in terms of adaptive rewiring of network connectivity, while representing neural activity by diffusion on the network: Where diffusion is intensive, shortcut connections are established, while underused connections are pruned. In binary networks, this process is known to steer initially random networks robustly to high levels of structural complexity, reflecting the global characteristics of brain anatomy: modular or centralized small world topologies. We investigate whether this result extends to more realistic, weighted networks. Both normally-and lognormally-distributed weighted networks evolve either modular or centralized topologies. Which of these prevails depends on a single control parameter, representing global homeostatic or normalizing regulation mechanisms. intermediate control parameter values exhibit the greatest levels of network complexity, incorporating both modular and centralized tendencies. The simulation results allow us to propose diffusion based adaptive rewiring as a parsimonious model for activity-dependent reshaping of brain connectivity structure.From neuronal synapses to white matter tracts 1 , brain anatomical networks are characterized by the structural properties of small-worldness 2,3 , modularity 4,5 and rich club organization 6,7 . The pervasiveness of these properties raises the question whether they result from a common principle 5,8 . We proposed that these properties are the product of adaptive rewiring 9-13, for a review14 . Adaptive rewiring captures a crucial property of how the brain's anatomical network is shaped over time. Whereas the mechanisms that shape the brain network show great variety, as they encompass brain growth 15 , development, as well as learning 16,for a review , they are alike in their common dependency on the network's functional connectivity, i.e. the statistical dependencies between the nodes' activities 12,17 . Adaptive rewiring formalizes this dependency in terms of graph theory, as it encompasses adding shortcut links to network regions with intense functional connectivity while pruning underused ones. These dynamical rewirings could be regarded as adaptive network optimization to function 18 .Whereas adaptive rewiring represents the dependency of structural connectivity on network activity, the reverse, viz. the dependency of activity on structural connectivity, has been the focus of intense investigation. Recently, it was proposed that a simple, linear equation can predict brain activity from anatomical connectivity 19 . The proposal describes traffic on a fixed anatomical network in terms of random walks. This allows the amount of traffic to be stochastically approximated in terms of diffusion on the graph. Jarman and colleagues 11 adopted a similar principle in an adaptive rewiring model. They represented the amount of flow transferred between nodes by a heat kernel. During each rewiring step, an edge wit...