During the course of a normal night of sleep, the human brain switches between deep and light sleep, and dreaming sleep, several times; confusional arousals occur when the brain becomes divided, literally, between sleeping and waking. Part of the brain wakes up, but another part remains deeply asleep. During a confusional arousal, a sleeper may talk, sit up in bed, scream, or even leave the bed and wander around—the proverbial sleepwalking, although that is less common than sleeptalking. Because development of the sleep stage switching mechanism occurs during the period from infancy to about ten years old, confusional arousals are most common in this age group. Current research confirms the validity of popular lore about sleeptalkers and sleepwalkers—that one should not attempt to awaken them. Despite the open eyes, despite the calm or agitated talking, sleeptalkers are deeply asleep. The recommended strategy is that there is no need to yell or try to wake up someone who is sleeptalking; just make sure they are safe and comfortable. In the morning, the sleeper will not remember their episode.
See also Sleep disorders entry in NIGHTMARES.