Aleman, André BCN Neuroimaging Centre, University Medical Centre Groningen, Groningen, The Netherlands.
Last reviewed:October 2019
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- Scope of hallucinations
- Hallucinations in the brain
- Top-down processing
- Magnetic stimulation
- Related Primary Literature
- Additional Reading
A sensory experience that occurs in the absence of corresponding external stimulation of the relevant sensory organ or organs. A hallucination is an apparent perception of something that is not present. It typically arises from a mental or nervous system disorder or as a result of certain drugs. In addition, the hallucinatory experience has a sufficient sense of reality to resemble a veridical (genuine) perception and occurs when one is awake; furthermore, one does not feel that one has direct and voluntary control over it. Thus, for example, a person who is hallucinating sees things that are not there or hears voices when nobody in the vicinity is speaking. Although visual and auditory hallucinations are most common, hallucinations of taste, smell, and touch can also occur. The exact mechanisms underlying the experience of hallucination remain elusive, but significant strides have been made in uncovering processes in the mind and brain that are associated with hallucinations (Fig. 1). See also: Brain; Cognition; Mental disorders; Nervous system disorders; Perception; Sensation; Sense organ
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