Micheli et al find that during sustained attention, successful near-threshold visual detection is predicted by increased phase synchrony between the frontal and temporal/parietal cortex.  They suggest that beta coherent states in the prefrontal cortex regulate top-down expectancy and coupling with posterior cortex facilitates the gating of that information.

Evidence for the role of beta in top-down selection continues to mount.

Micheli, Cristiano, et al. “Inferior-frontal cortex phase synchronizes with the temporal-parietal junction prior to successful change detection.” NeuroImage (2015).