Recent work has also begun to utilize the tools of graph theoretical analysis to characterize the effects of brain stimulation techniques on cortical network topology. Polania et al (2010) applied facilitatory anodal tDCS to the left primary motor cortex with the cathode situated over the contralateral orbit, and applied real versus sham stimulation. EEG was recorded before and after tDCS, during both resting state and performance of a simple motor task, and fcEEG between all electrode pairs was assessed using the synchronization likelihood connectivity measure (Stam & Dijk, 2002). The authors demonstrated that in the resting state networks, tDCS produced an increase in synchronization between the frontal areas within multiple frequency bands. A comparison of brain activity during performance of the motor task demonstrated increased synchronization within parieto-occipital and frontal regions of the left hemisphere in the θ and α bands, no change in the β and low-γ bands, and increased synchronization within the left premotor, motor and sensorimotor regions in the high-γ range. There was also significant interhemispheric desynchronization in the α, β and high-γ bands (Figure 12). Another
