More evidence (this time in humans) that top-down vs bottom-up cortical processing depends on synchrony in different frequency bands, lower frequencies (beta) for top-down and higher frequencies (gamma) for bottom-up. There was cross-frequency coupling such that gamma power in auditory cortex was modulated by phase of beta in the anterior cingulate (but not the other way around). Top-down and bottom-up processing alternattively dominated. Thus, the brain uses both frequency- and time-multiplexing to optimize directional flow of information.
