Fig. 3. Representative recordings from a chronically instrumented rat. Measurements during sleep (A +B ) and ketamine anesthesia (C +D ). Genioglossus electromyogram was higher during ketamine anesthesia compared with sleep. During ketamine anesthesia, strong respiratory activity was present during wakefulness and sleep. The electroencephalogram during nonrapid eye movement sleep and ketamine anesthesia appears similar (predominantly slow-wave sleep), but different from rapid eye movement sleep (predominantly θ waves). 5 s epoch. EEG = electroencephalogram; EMG = electromyogram; GG = genioglossus; NREM = nonrapid eye movement sleep; REM = rapid eye movement sleep.