hallucination

The apparent, often strong subjective perception of an object or event when no such stimulus or situation is present; may be visual, auditory, olfactory, gustatory, or tactile. [L. alucinor, to wander in mind]

- auditory h. a symptom frequently observed in a schizophrenic disorder consisting, in the absence of an external source, of hearing a voice or other auditory stimulus that other individuals do not perceive.

- command h. a symptom, usually auditory but sometimes visual, consisting of a message, from no external source, to do something.

- formed visual h. h. composed of scenes, often landscapes.

- gustatory h. the sensation of taste in the absence of a gustatory stimulus; may be seen in temporal lobe epilepsy.

- haptic h. the sensation of touch in the absence of stimuli; may be seen in alcoholic delirium tremens.

- hypnagogic h. h. occurring when going to sleep in the period between wakefulness and sleep; one of the components of narcolepsy.

- hypnopompic h. vivid hallucinations that occur when wakening from sleep; occurs with narcolepsy, but grouped with hypnagogic h..

- kinesthesia h. the sense of movement of one or more muscles, when no movement is taking place.

- lilliputian h. h. of reduced size of objects or persons.

- mood-congruent h. h. in which the content is mood appropriate.

- mood-incongruent h. h. that is not consistent with external stimuli; content is not consistent with either manic or depressed mood.

- olfactory h. false perception in smell.

- stump h. SYN: phantom limb pain.

- tactile h. false perception of movement or sensation, as from an amputated limb, or crawling sensation on the skin.

- unformed visual h. h. composed of sparks, lights, or bursting spheres of light.

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hal·lu·ci·na·tion hə-.lüs-ən-'ā-shən n

1) a perception of something (as a visual image or a sound) with no external cause usu. arising from a disorder of the nervous system (as in delirium tremens or in functional psychosis without known neurological disease) or in response to drugs (as LSD) compare DELUSION (2), ILLUSION (2a)

2) the object of a hallucinatory perception

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n.

a false perception of something that is not really there. Hallucinations may be visual, auditory, tactile, gustatory (of taste), or olfactory (of smell). They may be provoked by psychological illness (such as schizophrenia) or physical disorders in the brain (such as temporal lobe epilepsy or stroke) or they may be caused by drugs or sensory deprivation. Hallucinations should be distinguished from dreams and from illusion (since they occur at the same time as real perceptions and are not based upon real stimuli).

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hal·lu·ci·na·tion (hə-loo″sĭ-naґshən) [L. hallucinatio; Gr. alyein to wander in the mind] a sense perception without a source in the external world; a perception of an external stimulus object in the absence of such an object.