The Distribution of EEG Frequencies in REM and NREM Sleep Stages in Healthy Young Adults

Period-analyzed electroencephalographic (EEG) activity was evaluated in 11 men and 11 women to explore the distribution of EEG frequencies during sleep and potential gender differences. Significant stage-of-sleep main effects were noted for both incidence and amplitude measures. Power measures seemed to best differentiate between non-rapid eye movement (NREM) stages, although incidence measures showed roughly the same distributions across sleep stages. Beta incidence and amplitude was highest in stage 1 sleep followed in descending order by rapid eye movement (REM), stage 2, and slow-wave sleep (SWS). Delta incidence and amplitude were highest in SWS, with slightly lower values in stage 2. Interestingly, REM was characterized by higher incidence and amplitude delta than those found in stage 1 sleep. EEG variables did not show striking sex differences in any sleep stage, although a global measure of delta power in NREM sleep was higher among women. Hemispheric asymmetries were small throughout REM and NREM stages. These findings suggest that period analysis provides a detailed description of EEG frequency characteristics during sleep but does not reveal dramatic gender differences.