Raw electroencephalogram (EEG) data of sleep-wake states. A, C, and E show representative EEG and electromyogram tracings. For each, the top two rows of signals represent frontal and parietal EEG, respectively, and lower row represents electromyogram. B, D, and F, Raster plots of sleep–wake states as a function of time for wakefulness (in blue: B), non–rapid eye movement (NREM) sleep (in black: D), and rapid eye movement (REM) sleep (in red: F). On the x axis, time of the day. On the y axis, animals that recordings were obtained from. Each vertical line represents a bout. Symbol indicates “light on,” Symbol • indicates “light off.” Yellow dotted line divides the 24-h recording period in two 12-h intervals (at the time of light off). (A ) Tracings from an awake sham-control animal. Note the low-amplitude, high-frequency, and desynchronized EEG activity combined with elevated muscular tone. (B ) Wakefulness raster plot of sham-control and Anesthesia 2h rats. (C ) Transition from awake to NREM sleep in an anesthesia-exposed rat. Note the change from low-amplitude, high-frequency EEG with elevated muscular tone to high-amplitude, low-frequency EEG activity with reduced motor tone. (D ) NREM sleep raster plot of sham-control and Anesthesia 2h rats. (E ) Transition from NREM to REM sleep in an anesthesia-treated rat. Note the change from high-amplitude, low-frequency EEG activity of NREM sleep to low-amplitude, high-frequency, synchronized EEG activity coupled with minimal to absent muscle tone of REM sleep. (F ) REM sleep raster plots of sham-control and Anesthesia 2h animals. N = 11 sham-control and 10 Anesthesia 2h rats.