  Converging research suggests that the resting brain operates at the cusp of
dynamic instability signified by scale-free temporal correlations. We asked if
the scaling properties of these correlations differ between amplitude and phase
fluctuations, which may reflect different aspects of cortical functioning.
Using source-reconstructed magneto-encephalographic signals, we found power-law
scaling for the collective amplitude and for phase synchronization, both
capturing whole-brain activity. The temporal changes of the amplitude comprise
slow, persistent memory processes, whereas phase synchronization exhibits less
temporally structured and more complex correlations, indicating a fast and
flexible coding. This distinct temporal scaling supports the idea of different
roles of amplitude and phase in cortical functioning.
