Awakening thresholds for electrical brain stimulation in five sleep-waking stages in the cat

Awakening thresholds during the different stages of a particular 5-stage sleep-waking classification in the cat were determined by electrical stimulation through electrodes implanted in the brain. Only areas from which orienting behaviour was elicited when stimulated during the alert waking (W-1) stage were used for the awakening threshold studies. The stages compared with W-1 were W-2, SWS-1, SWS-2 and REM sleep. There were stepwise increments in the awakening thresholds from one stage to the next in the predicted order from W-2 to REM sleep. There was some variation between structures, but the threshold increments were consistent and support the validity of the 5-stage sleep-waking classification.