The finding that brain stimulation techniques modify the activity of entire networks argues against the view that noninvasive brain stimulation techniques produce largely locally restricted modifications in cortical excitability. Rather, noninvasive brain stimulation techniques modify the activity and connectivity of distributed cortical networks, extending well beyond the region of direct stimulation. Recognition of this fact implies that the findings of previous studies utilizing brain stimulation techniques to probe the function of specific regions may need to be reinterpreted. Also, more effective utilization of noninvasive brain stimulation techniques in both research and clinical therapeutics will require exploration and evaluation of how focal brain stimulation modifies network activities as a function of baseline state, stimulation protocol, baseline functional connectivity, task, and region of stimulation.
