Fig. 13

Power spectral density plots pre- and post-ICA. A Power spectral density plot for 1 min of slow-wave sleep (SWS) and 1 min of rapid-eye-movement sleep (REM) (see Fig. 11 for raw waveforms) with significant heart rate artifacts in the electroencephalogram (EEG). The plot compares spectral power over frequency for raw EEG (violet), EEG pruned with ICA (blue), and the IC that maximally expressed brain activity (green) for both SWS (bold upper line) and REM (thin lower line). This demonstrates the greater discriminatory power between SWS and REM in the delta frequency range in EEG signals processed with ICA (shaded areas). B Power spectral density (PSD) plot for 1 min of SWS where there was no significant heart rate artifact in the EEG, demonstrating the spectral features of the raw electrocardiogram (ECG) signal, apparent in the raw EEG signal in 13A. In addition, left and right raw EEG signals show that the spectral features of SWS are primarily preserved in the maximal brain IC, shown in 13A. Note the different horizontal and vertical scales of A and B