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a sensory impression (sight, touch, sound, smell, or taste) that has no basis in external stimulation. Hallucinations can have psychologic causes, as in mental illness, or they can result from drugs, alcohol, organic illnesses, such as brain tumor or senility, or exhaustion. When hallucinations have a psychologic origin, they usually represent a disguised form of a repressed conflict. adj. adj hallu´cinative, hallu´cinatory.
auditory hallucination a hallucination of hearing; the most common type.
gustatory hallucination a hallucination of taste.
haptic hallucination tactile hallucination.
hypnagogic hallucination a vivid, dreamlike hallucination occurring at sleep onset.
hypnopompic hallucination a vivid, dreamlike hallucination occurring on awakening.
kinesthetic hallucination a hallucination involving the sense of bodily movement.
olfactory hallucination a hallucination of smell.
somatic hallucination a hallucination involving the perception of a physical experience occurring within the body.
tactile hallucination a hallucination of touch.
visual hallucination a hallucination of sight.
hallucination occurring when going to sleep in the period between wakefulness and sleep; one of the components of narcolepsy.
Synonym(s): hypnagogic image
Etymology: Gk, hypnos, sleep, agogos, leading
a vivid image that occurs while falling asleep.
hyp·na·gog·ic hal·lu·ci·na·tion(hip'nă-goj'ik hă-lū'si-nā'shŭn)
A common symptom in narcolepsy characterized by vivid, dreamlike perceptions occurring with sleep onset. Often these perceptions involve fearful situations that are described as realistic and include visual, tactile, and auditory hallucinations.