Continuous EEG records brain activity when the subject is at rest or in relaxed wakefulness. Resting-state EEG is primarily analyzed in the frequency domain, as no specific periodicity can be imposed using fast Fourier transform-based methods. Traditionally, EEG is decomposed into the following frequency bands: delta (0–3 Hz), theta (4–7 Hz), alpha (8–12 Hz), beta (13–28 Hz), and gamma (>29 Hz), and each band reflects different types of brain activity. Variations in relative power of these specific frequency bands can indicate level of consciousness, psychological state, or presence of neurological disorders (Nunez, 1995; Niedermayer and Lopes Da Silva, 1999). Resting theta rhythm has its maximum power in the posterior scalp region but is not prevalent in the normal adult waking EEG. Alpha band is a posterior dominant rhythm that emerges with closing of the eyes and relaxation and attenuates with eye opening or mental exertion. Hence, it is described as an index of relaxed wakefulness. Alpha is slower in young children (closer to theta frequency) and increases with age into high alpha frequencies and is a key feature of EEG
