Frequency spectral analysis
Frequency spectral analysis was performed using a fast Fourier transform
(1000-point) algorithm. The absolute power spectral density (PSD, dB,
10log10(V2/Hz)) for each channel was calculated based
on the periodogram. Relative PSD (rPSD) was computed by normalizing the
total power over the entire frequency range. The absolute and relative
PSDs were averaged across channels within groups to measure the global
comparisons between groups in each frequency band. A group comparison of
the PSDs for each channel was also performed.