Macroscopic activity states in brain networks mediate cognition and 
behavior. Pathological changes in these network dynamics are associated 
with both neurological and psychiatric disorders. Studying how cellular 
elements give rise to activity dynamics represents a promising approach 
to understanding and eventually treating disorders of the central 
nervous system. Here, we introduce large-scale simulations of neuronal 
networks to study (1) how network topology gives rise to network 
dynamics and (2) how brain stimulation can be used to modulate and 
enhance macroscopic network dynamics. We demonstrate that global weak 
perturbations of neuronal signaling is a powerful brain stimulation 
approach and show experimental results from animal electrophysiology and 
a human trial that demonstrate the feasibility of this novel brain 
stimulation paradigm based on transcranial current stimulation.