EEG Bands During Wakefulness, Slow-Wave and Paradoxical Sleep as a Result Of Principal Component Analysis in Man

Abstract

Human electroencephalogram (EEG) has been divided in bands established by visual inspection that frequently do not correspond with EEG generators nor with functional meaning of EEG rhythms. Power spectra from wakefulness, stage 2, stage 4 and paradoxical sleep of 8 young adults were submitted to Principal Component Analyses to investigate which frequencies covaried together. Two identical eigenvectors were identified for stage 2 and stage 4: 1 to 8 Hz and 5 to 15 Hz (87.95 and 84.62 % of the total variance respectively). Two eigenvectors were extracted for PS: 1 to 9 Hz and 10 to 15 Hz (81.62% of the total variance). Three eigenvectors were obtained for W: with frequencies between 1 to 7 Hz, 7 to 11 Hz, and 12 to 15 Hz (78.32% of the total variance). Power for all frequencies showed significant differences among vigilance states. These results indicate that slow wave activity can oscillate at higher frequencies, up to 8 Hz, and that spindle oscillations have a wider range down to 5 Hz. No theta band was independently identified, suggesting either that delta and theta oscillations are two rhythms under the same global influence, or that the traditional division of theta band in the human cortical EEG is artificial. Alpha as a band was identified only during wakefulness. Principal component analysis upon spectral densities extracted broad bands different for each vigilance state and from traditional bands, consistent with functional significance of EEG and with frequencies of generators of rhythmic activity obtained in cellular studies in animals.

Rhythmic hippocampal slow oscillation characterizes REM sleep in humans

“…EEG is artificial (Corsi-Cabrera et al, 2000). Our results suggest that a well-defined range of delta activity (1.5-3 Hz) in temporolateral leads is a basic characteristic of REM sleep, but has different sources from that of NREM delta oscillation.…”

Power and coherent oscillations distinguish REM sleep, stage 1 and wakefulness

“…At least ten 2-s epochs were analyzed for each subject and condition. Previous studies have demonstrated that 10 epochs of 2 s of EEG satisfy both stationarity and stability for spectral analysis (Cohen, 1977;Mö cks and Gasser, 1984;Corsi-Cabrera et al, 2000). Signals were Fast Fourier transformed and power was averaged over 1 Hz to obtain EEG absolute power spectra (AP) with 1 Hz resolution from 1 to 50 Hz for each subject, physiological state and derivation.…”

Assessment of Wakefulness and Brain Arousal Regulation in Psychiatric Research

“…According to original conceptions by Bente [8] and Roth [9] , the following EEG vigilance stages can be observed during the transition from high alertness to relaxed wakefulness to drowsiness and finally sleep onset: • Stage 0: desynchronized non-alpha EEG in the absence of slow horizontal eye movements; found during an activated state (e.g. mental effort) • Stage A (with substages A1, A2, A3): EEG with dominant alpha activity corresponding to relaxed wakefulness, with decreasing vigilance, slight slowing of alpha activity and shift from occipital to more anterior cortices • Stage B1: non-alpha EEG with low amplitude (similar spectral composition as stage 0) but with presence of slow horizontal eye movements; drowsiness • Stage B2/3: non-alpha EEG with predominant theta/ delta activity, occasional occurrence of vertex waves; drowsiness and transition to sleep onset • Stage C: commencing with occurrence of sleep spindles or K complexes; sleep onset More recent studies on changes of EEG activity during the transition from active wakefulness to sleep onset endorse this classification [36][37][38][39][40][41][42][43][44][45][46] .…”