Sleep-talking
Somniloquy, commonly referred to as sleep-talking, is a parasomnia that refers to talking aloud while asleep. It can range from simple mumbling sounds to loud shouts and long, frequently inarticulate speeches, and can occur many times during a sleep cycle. As with sleepwalking and night terrors, sleep-talking usually occurs during delta-wave NREM sleep stages or during temporary arousals therefrom. It can also occur during the REM sleep stage, at which time it represents what sleep therapists call a "motor breakthrough" (see sleep paralysis) of dream speech: words spoken in a dream are spoken out loud . Depending on its frequency, this may or may not be considered pathological. All motor functions are typically disabled during REM sleep thus, motoric, i.e., verbal elaboration of dream content could be considered an REM behavior disorder. Presentation. Associated conditions. Sleep-talking can occur by itself (i.e., idiopathic) or as a feature of another sleep disorder such as: Causes. In 1966, researchers worked to find links between heredity and sleep-talking. Their research suggests the following: Sleep-talking by itself is typically harmless; however, it can wake others and cause them consternation—especially when misinterpreted as conscious speech by an observer . If the sleep-talking is dramatic, emotional, or profane it may be a sign of another sleep disorder. Sleep-talking can be monitored by a partner or by using an audio recording device; devices which remain idle until detecting a sound are ideal for this purpose. Polysomnography (sleep recording) shows that episodes of sleep talking that can occur in any stage of sleep. Stress can also cause sleep talking. In one study, about 30% of people who suffered from PTSD (post-traumatic stress disorder) talk in their sleep. A 1990 study showed that Vietnam War veterans having PTSD report talking  more in their sleep than in people without PTSD. Sleep-talking can also be caused by depression, sleep deprivation, day-time drowsiness, alcohol, and fever. It often occurs in association with other sleep disorders such as confusional arousals, sleep apnea, and REM sleep behavior disorder. In rare cases, adult-onset sleep-talking is linked with a psychiatric disorder or nocturnal seizure. Prevalence. Sleep-talking is very common and is reported in 50% of young children at least once a year. A large percentage of people progressively sleep-talk less often after the age of 25. A sizable proportion of people  without any episode during their childhood begin to sleep-talk in adult life. Sleep-talking may be hereditary. In a study reporting the prevalence of sleep-talking in childhood, the authors reported that the frequency of sleep-talking differs between children. About half of the children have sleep-talking episodes at least once a year, but less than 10% of children present sleep-talking every night, whereas 20% to 25% talk in their sleep at least once a week. In addition, they did not find any difference between gender or socioeconomic class. However, valid estimation of the prevalence of this  phenomenon is difficult as the sleep-talker either does not remember or are not aware of their sleep-talking. The same uncertainty exists concerning the age of onset because early occurrences may have escaped notice. Thus, there are disparate results regarding its prevalence in the literature. Treatment. Usually, treatment is not required for sleep-talking because it generally does not disturb sleep or cause other problems. One behavioral treatment has shown results in the past. Le Boeuf (1979) used an automated auditory signal to treat chronic sleep-talking in a person who had talked in his sleep for 6 years . An aversive sound was produced for 5 seconds when he started talking in his sleep. Sleep-talking was rapidly eliminated, and the person demonstrated no adverse effects of treatment. Research. Although extremely rare, people who experience sleep-talking may sometimes speak in another language. This phenomenon known only as "different-language sleep-talk" is currently under research. This occurrence will most times be in a language that the person has obtained earlier on in life, although it is also possible to different-language sleep-talk a second language that one has learned later in one's childhood or pre-adulthood . It is impossible for someone experiencing different-language sleep-talk to speak in a language that they do not know or have not learned. The most common cases of people who experience different-language sleep-talk occur in teen to adulthood and will usually range anywhere between the ages of 17 to 26. Different-language sleep-talk is non-harmful and usually affects someone that sleep-talks on a regular basis. In literature. Sleep-talking appears in Shakespeare's "Macbeth", the famous sleepwalking scene. Lady Macbeth, in a "slumbery agitation", is observed by a gentlewoman and doctor to walk in  her sleep and wash her hands, and utter the famous line, "Out, damned spot! out, I say!" (Act 5, Scene 1). Sleep-talking also appears in "The Childhood of King Erik Menved", a 19th-century historical romance by Danish author Bernhard Severin Ingemann. In the story, a young girl named Aasé has the prophetic power of speaking the truth in her sleep. In an 1846 English translation, Aasé is described thus: Walt Whitman wrote a now-lost novel based on Ingemann's romance, which he titled "The Sleeptalker". In Lewis Carroll's "Alice's Adventure's in Wonderland", Chapter VII , The Dormouse talks in his sleep, or at least seems to, and even sings in his sleep: