Phase offset determines alpha modulation of gamma phase coherence and hence signal transmission.

We find conditions for optimal phase coherence among sums of phase-offset sine wave pairs of two frequencies, e.g., gamma and alpha. Optimal phase coherence occurs when the respective phase offsets match. Then, using stochastic rate models instead of firing models for both cortical and pulvinar activity, we show that for roughly matching phase offsets of alpha and gamma oscillations there is optimal phase coherence and information transmission between modelled cortical regions.