Fig. 3

Pipeline of measurement of respiration-related EEG activity. (A) An example of an EEG time series is presented in black, and the corresponding respiratory time series (nasal airflow) is presented in blue. Inspiratory and expiratory epochs, deduced from respiratory feature detection, are shown in green and red spans, respectively. Black vertical dashed lines indicate the separation between two successive respiratory cycles. Note the variability in the duration of the eight successive respiratory epochs/cycles, which would prevent the averaging of respiratory-based EEG epochs. (B) Time series are rescaled into respiratory phase-based series through linear interpolation of traces between detected respiratory timestamps (IE and EI transitions). Therefore, each respiration-based EEG epoch has the same length and can be averaged across epochs/cycles. (C) The averaged EEG cyclical dynamic along the respiratory phase is displayed in black. The total amplitude of this trace can be computed (max–min) to extract the strength of modulation of EEG amplitude by respiration: “EEG Modulation Amplitude”. AU, arbitrary units; Respi, respiration.