In recent decades, a range of noninvasive techniques for studying and manipulating brain activity have been developed. EEG, PET and fMRI are complementary methods of assessing neural activity. A number of analytic techniques have been applied to data collected using these methods to help delineate the brain’s functional connectivity, i.e. the interactions between different brain regions both at rest and during performance of various tasks, and their use has led to the understanding that cognitive functions are carried out by widespread cortical networks. The same decades have witnessed the introduction of TMS and tDCS, two techniques which rely on electromagnetic principles to noninvasively modulate brain activity. A number of interesting studies have combined brain stimulation techniques with neuroimaging modalities to evaluate and modify brain activity. As such, they provide powerful tools for probing the connectivity of different cortical regions, and for causally investigating the role of network activity in various cognitive functions. These studies have also demonstrated that TMS and tDCS affect not only the focal region to which stimulation is being applied, but also affect widespread cortical areas that
