Fig. 6,

Example cross-frequency coherence between oscillatory power and oscillatory phase as a function of velocity for the lacunosum-moleculare. As velocity increases, there are low-frequency interactions between theta and its harmonics (below 40 Hz). Because harmonics by definition are integer, phase-locked components to a fundamental oscillation, and because the deformation of theta from sinusoid to sawtooth increases with velocity (Buzsáki et al. 1983; Sheremet et al. 2016; Terrazas et al. 2005), this effect is to be expected. Interestingly, there is a notable increase in the coupling between theta phase and gamma power, as well as theta harmonic phase and gamma power, with velocity. Our effect is largely in agreement with the observations of Michaels et al. (2018).