Sleepwalking, also known as somnambulism or noctambulism, is a phenomenon of combined sleep and wakefulness. It is classified as a sleep disorder belonging to the parasomnia family. It occurs during slow wave stage of sleep, in a state of low consciousness, with performance of activities that are usually performed during a state of full consciousness. These activities can be as benign as talking, sitting up in bed, walking to a bathroom, consuming food, and cleaning, or as hazardous as cooking, driving a motor vehicle, violent gestures and grabbing at hallucinated objects.Although sleepwalking cases generally consist of simple, repeated behaviors, there are occasionally reports of people performing complex behaviors while asleep, although their legitimacy is often disputed. Sleepwalkers often have little or no memory of the incident, as their consciousness has altered into a state in which memories are difficult to recall. Although their eyes are open, their expression is dim and glazed over. This may last from 30 seconds to 30 minutes.Sleepwalking occurs during slow-wave sleep (N3) of non-rapid eye movement sleep (NREM sleep) cycles. It typically occurs within the first third of the night when slow-wave sleep is most prominent. Usually, it will occur once in a night, if at all.
This same group published an article twelve years later with a new conclusion: "Sleepwalking, contrary to most belief, apparently has little to do with dreaming. In fact, it occurs when the sleeper is enjoying his most oblivious, deepest sleep—a stage in which dreams are not usually reported." More recent research has discovered that sleepwalking is actually a disorder of NREM (non-rapid eye movement) arousal. Acting out a dream is the basis for a REM (rapid eye movement) sleep disorder called REM Behavior Disorder (or REM Sleep Behavior Disorder). More accurate data about sleep is due to the invention of technologies, such as the electroencephalogram (EEG) by Hans Berger in 1924 and BEAM by Frank Duffy in the early 1980s.In 1907, Sigmund Freud spoke about sleepwalking to the Vienna Psychoanalytic Society (Nunberg and Federn). He believed that sleepwalking was connected to fulfilling sexual wishes and was surprised that a person could move without interrupting their dream. At that time, Freud suggested that the essence of this phenomenon was the desire to go to sleep in the same area as the individual had slept in childhood. Ten years later, he speculated about somnambulism in the article "A Metapsychological Supplement to the Theory of Dreams" (1916–17 [1915]). In this essay, he clarified and expanded his hypothetical ideas on dreams. He described the dream as a fragile equilibrium that is destabilized by the repressed unconscious impulses of the unconscious system, which does not obey the wishes of the ego.