- Also known as sleep dream, night dream, and nocturnal dream. All four terms are used interchangeably to denote an endogenously mediated perceptual experience occurring physiologically during sleep. Dreaming can be defined as the creation of percepts during sleep, in a format which the dreamer tends to experience as a participant rather than a mere observer. The dream's content tends to be primarily visual in nature (hence the term * sleep dream vision), although the other sensory modalities may be involved as well. Near the end of the 19th century, dreams were divided into associative dreams and Nervenreizträume (i.e. 'nerve-impulse dreams'). Both terms were introduced in 1882 by the German philosopher Heinrich Spitta (1849-1929). Spitta uses the term associative dream to denote a dream that borrows its content in an associative manner from intrapsychic data such as wishes, fears, memories, and fantasies. Envisaging associative dreams as de novo perceptual experiences, Spitta conceptualizes these as analogous to hallucinations. The term Nervenreiztraum is used by him to denote the type of dream prompted by external perceptual stimuli (such as the sound of the rain or a door closing, or the feeling of a cat jumping onto the bed). Therefore, Spitta likens Nervenreizträume to * illusions. Dreams are associated primarily, although not exclusively, with periods of rapid eye movement (i.e. the REM state of paradoxical sleep). Their mediation is associated primarily with neurophysiological activity in the pons. The term *lucid dream is used to denote a dream during which the individual is aware that he or she is dreaming while the dream is in progress. Traditionally dreams are distinguished from * hallucinations proper by their occurrence during sleep, as well as by their capacity to replace the whole sensory environment. Except for *panoramic or * scenic hallucinations, hallucinations tend to coincide (and often to blend in) with regular sense perceptions. However, the * continuum hypothesis put forward by the French classical scholar and dream researcher Louis-Ferdinand-Alfred Maury (1817-1892) suggests that dreams and hallucinations are not distinct but continuous phenomena. Moreover, it has been suggested by a small minority of authors that dreams should be granted the status of hallucinations. For example, the American psychiatrist and sleep researcher William Charles Dement (b. 1928) asserts that "there can be little question that dreams qualify as hallucinations." The term night dream is used in opposition to the term * daydream. The global cessation of dreaming following bilateral occipital infarction is known as the * Charcot-Wilbrand syndrome.ReferencesDement, W.C. (1965). Perception during sleep. In: Psychopathology ofperception.Editedby Hoch, P.H., Zubin, J. New York, NY: Grune & Stratton.Hartmann, E. (1998). Dreams and nightmares. The new theory on the origin and meaning of dreams. New York, NY: Plenum Trade.Maury, L.F.A. (1865). Le sommeil et les rêves. Études psychologiques sur ces phénomènes et les divers états qui s'y rattachent. Troisième édition. Paris: Librairie Académique Didier et Cie., Libraires-Éditeurs.Spitta, H. (1882). Die Schlaf- und Traumzustände der menschlichen Seele. Freiburg i.B.: Mohr.Schiller, F. (1985). The inveterate paradox of dreaming. Archives ofNeurology, 42, 903-906.
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