Pascal Fries and crew add to the mounting evidence that slow vs fast oscillations subserve feedback vs feedforward information flow in the cortex.

Michalareas, G., Vezoli, J., van Pelt, S., Schoffelen, J. M., Kennedy, H., & Fries, P. (2016). Alpha-Beta and Gamma Rhythms Subserve Feedback and Feedforward Influences among Human Visual Cortical Areas. Neuron.