Since the early research on EEG analysis, it has been
observed that the regions of a healthy human cortex have
their own intrinsic rhythms in the range of 0.5 − 40Hz.
In general, five main rhythms can be detected from an EEG
recording: Delta (δ) 0.5 − 4Hz, Theta (θ) 4 − 8Hz, Alpha (α)
8 − 14Hz, Beta (β) 14 − 30Hz and Gamma (γ ) over 30Hz.
In Fig. 2 examples of δ, θ , α, β, and γ rhythms acquired
through the O2 channel using a resting state with closed
eyes protocol are depicted. The amount of activity in different