Recently, however, investigators have found evidence for regional- and task-dependent variation of the dominant low frequency rhythm providing the phase for phase-amplitude CFC. For example, using magnetoencephalography (MEG), Osipova and colleagues observed that gamma power was locked to posterior alpha phase, not theta phase [45]. Similarly, Cohen et al. observed alpha/gamma phase-amplitude coupling in the human nucleus accumbens [48]. Furthermore, the amplitude frequency need not be in the gamma range: Cohen and colleagues found that delta/theta phase modulated alpha/beta amplitude in human medial frontal cortex, and that phase-amplitude CFC strength in this competitive decision making task differed between losses and wins [49].
