Overall, these results highlight that neuronal oscillations and functional connectivity at low frequencies are strongly implicated in attentional mechanisms and are possibly related to functional inhibition through feedback mechanisms (Jensen and Mazaheri, 2010). Nevertheless, further investigation is needed to clarify the specific role of the different frequency (sub-)bands observed in long-range phase coupling. Indeed, while it is conceivable that gamma frequencies are implicated in bottom-up information processing, still poor evidence demonstrate the involvement of long-range gamma-band coherence in top-down processing (Siegel et al., 2008; Gregoriou et al., 2009) and further investigation are needed to associate different frequency bands with specific mechanism of feedback and feed-forward interactions (Siegel et al., 2012).
