Figure 1. Typical recordings of respiratory flow, instantaneous breathing frequency (breaths/min), EMG, and EEG obtained in 1 animal throughout the recording session (A), during non-REM (B), and REM sleep (C).

The upper line in panel A shows the scoring of sleep/wake states (W = wake, non-REM sleep, and REM sleep). Note the numerous sighs that appear as fine peaks during sleep in panel A, and the typical regular breathing pattern in non-REM sleep (B). During REM sleep, the breathing pattern had bouts of irregular activities (C).