Amplitude-amplitude CFC has also been observed [24, 32, 33], but despite correlations with behavior, the functional role of amplitude-amplitude CFC remains unclear. Phase-amplitude CFC, on the other hand, has functional correlations and plausible physiological mechanisms. Low frequency phase reflects local neuronal excitability, while high frequency power increases reflect either a general increase in population synaptic activity (broad-band power increase) or the selective activation of a connected neuronal subnetwork (narrow-band power increase).
