Figure 1.

State-dependent modulation of breathing in urethane-anesthetized rats. A, Long-term EEG recordings at nCTX and HPC sites and corresponding power spectrograms, respiratory airflow, and breathing rate (bpm) show the rhythmic alternation of brain activity and the associated changes in respiratory flow and breathing frequency across brain states. Spectrograms indicate the prevalence of power at ∼1 Hz in both nCTX and HPC during nREM-like state and the prevalence of electrical power at ∼4 Hz in the HPC during REM-like states. The transition state is characterized by weak nCTX (1 Hz) and HPC (3–4 Hz) power. Schematic blocks at the bottom of the plot indicate time spent in REM-like (red), transition (gray), and nREM-like (black) epochs. Dashed vertical gray lines indicate the time point from which the traces displayed below are taken. Magnification of traces in REM-like (left), transition (middle), and nREM-like (right) states. B, Power spectral analysis for nCTX (top) and HPC (bottom) during nREM-like, REM, and transition states further indicate the prevalence of ∼1 Hz power in nCTX and HPC during nREM-like state and the prevalence of ∼4 Hz power in HPC during REM-like events. C–G, Average pooled period, CV of the period, tidal volume, minute ventilation, and sigh rate in REM-like (red), transition (gray), and nREM-like (black) epochs. Asterisks indicate statistical significance (p < 0.05) of states (REM-like or transition) relative to nREM-like epochs. C, D, n = 23; E, F, n = 15; G, n = 18.