The functional role of alpha-band activity in attentional processing: the current zeitgeist and future outlook

Electrophysiological activity measured at the scalp surface using electroencephalography or magnetoencephalography (EEG or MEG) contains prominent ongoing rhythmic activity across a mixture of different frequency bands. This rhythmic oscillatory activity is present during both rest and task performance. The most visible rhythm in the adult human brain is in the band between approximately 8-12 Hz, and is referred to as alpha activity. While sometimes dismissed by neurophysiologists as a nuisance biological artefact, since it often interferes with the recording of event-related potentials (ERPs), there has been an explosion of research linking it to specific functional roles in cognition and behavior over the past two decades. Here, we review some of the research into the functional significance of alpha oscillations with respect to attention and expectation. We focus our discussion on how the amplitude and phase of alpha activity might be involved in the prioritization of relevant sensory input. In addition to summarizing the literature, we also endeavor to provide a critical appraisal as well as highlight limitations and conceptual gaps in the field.