“…Besides absolute power spectral density (A‐PSD) of all electrodes, the relative power spectral density (R‐PSD) was also calculated. The R‐PSD, which was supposed to reduce session/subject variability, represented by the spectral ratios which could be defined as where R j , b is the R‐PSD of senor j, P j , b is the average A‐PSD of band b in sensor j, b∈{δ, θ, α, β, γ}.…”