The human brain is highly organized within networks. Functionally related neural-assemblies communicate by oscillating synchronously. Intrinsic brain activity contains information on healthy and damaged brain functioning. This thesis investigated the relationship between functional networks and behavior. Furthermore, we assessed functional network plasticity after brain damage and as a result of brain stimulation. In different groups of patients we observed reduced functional connectivity between regions involved with the coordination of the affected behavior and the rest of the brain. Network coherence in patients and healthy participants correlated linearly with corresponding behavioral performance. Diverse disease-related mechanisms of neuroplasticity were identified. Based on these findings we conclude that network imaging with EEG reveals important information on neural organization and is correlated with behavior. This opens new possibilities for clinics in general and in neurorehabilitation in particular. Our results suggest new perspectives for the implication of TMS as a part of a neuro-rehabilitative program.