ABSTRACT
The electroencephalography (EEG) typically consists of a complex waveform that includes a mixture of frequencies. However, two considerations motivate us to identify specific components. The first is that often a particular type of wave dominates, and is visually prominent. The second consideration is that when frequency transforms or filters are used, it is possible to isolate a component band, even in the presence of other components. The primary EEG complements have been identified through clinical and research experience, and the associated frequency ranges have come along afterward. The frequency bands, therefore, describe the complements but do not define them. An important distinction must be made between alpha activity and brain activity in a brain region. Alpha activity is associated with reduced brain activation; when alpha waves are present, that location is in an idling state, and hence is less active.
