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Related to Hypnagogic hallucination: narcolepsy, hypnopompic hallucination
See: figment, insanity, phantom

HALLUCINATION, med. jur. It is a species of mania, by which "an idea reproduced by the memory is associated and embodied by the imagination." This state of mind is sometimes called delusion or waking dreams.
     2. An attempt has been made to distinguish hallucinations from illusions; the former are said to be dependent on the state of the intellectual organs and, the latter, on that of those of sense. Ray, Med. Jur. Sec. 99; 1 Beck, med. Jur. 538, note. An instance is given of a temporary hallucination in the celebrated Ben Johnson, the poet. He told a friend of his that he had spent many a night in looking at his great toe, about which he had seen Turks and Tartars, Romans and Carthagenians, fight, in his imagination. 1 Coll. on Lun. 34. If, instead of being temporary, this affection of his mind had been permanent, he would doubtless have been considered insane. See, on the subject of spectral illusions, Hibbert, Alderson and Farrar's Essays; Scott on Demonology, &c.; Bostock's Physiology, vol. 3, p. 91, 161; 1 Esquirol, Maladies Mentales, 159.

References in periodicals archive ?
Seventy-four percent of these narcoleptics reported hypnagogic hallucinations, 71% cataplexy, 53% sleep onset paralysis and 44% awakening paralysis.
The patient was a 6-year old female who was hospitalized with the written consent of her parents because of visual hypnagogic hallucinations and other symptoms that had gradually exacerbated over the last 10 months.
Narcolepsy is classically a tetrad of symptoms including EDS, cataplexy, sleep paralysis, and hypnagogic hallucinations.
Clinicians have also reported cases of narcolepsy with prominent hypnagogic hallucinations that were mistakenly diagnosed as schizophrenia.
Excessive daytime sleepiness generally persists throughout life, but sleep paralysis and hypnagogic hallucinations may not.
8,9) Its 4 classic symptoms are EDS, cataplexy (a sudden drop in muscle tone that is triggered by emotional factors), sleep paralysis (a generalized flaccid paralysis that happens slightly before or at the time of falling asleep or on awakening), and hypnagogic hallucinations (hallucinations that occur while falling asleep).
Since Gelineau's initial description, the definition of narcolepsy has changed slightly to encompass these four symptoms: excessive sleepiness and/or uncontrolled episodes of overwhelming sleepiness (often called "sleep attacks"); hypnagogic hallucinations (realistic imagery occurring with the onset of sleep); sleep paralysis (inability to move just as one is awakening or going to sleep); and cataplexy (sudden, brief loss of muscle tone triggered by strong emotions).
Hypnagogic hallucinations - vivid, realistic imagery occurring just as a person is falling asleep
The recognition of two additional features, hypnagogic hallucinations (the onset of dreams while still awake) and sleep paralysis (a temporary loss of muscle tone or an inability to perform voluntary movements either at sleep onset or upon awakening), were added by Yoss and Daly in 1957.