(the Institute of Behavioural Sciences, Semmelweis University)
Power spectra of sleep electroencephalograms (EEG) comprise two main components: a
decaying power-law corresponding to the aperiodic neural background activity, and
spectral peaks present due to neural oscillations. “Traditional” band-based spectral
methods ignore this fundamental structure of the EEG spectra and thus are susceptible
to misrepresenting the underlying phenomena. A fitting method that attempts to separate
and parameterize the aperiodic and periodic spectral components called “fitting oscillations
and one over f” (FOOOF) was applied to a set of annotated whole-night sleep EEG recordings
of 251 subjects from a wide age range (4–69 years). Most of the extracted parameters
exhibited sleep stage sensitivity; significant main effects and interactions of sleep
stage, age, sex, and brain region were found. The spectral slope (describing the steepness
of the aperiodic component) showed especially large and consistent variability between
sleep stages (and low variability between subjects), making it a candidate indicator
of sleep states. The limitations and arisen problems of the FOOOF method are also
discussed, possible solutions for some of them are suggested.
