Hostname: page-component-7c8c6479df-94d59 Total loading time: 0 Render date: 2024-03-28T23:43:27.833Z Has data issue: false hasContentIssue false

Why people see things that are not there: A novel Perception and Attention Deficit model for recurrent complex visual hallucinations

Published online by Cambridge University Press:  22 December 2005

Daniel Collerton*
Affiliation:
South of Tyne and Wearside Mental Health NHS Trust, Bensham Hospital, Gateshead NE8 4YL, United Kingdom
Elaine Perry*
Affiliation:
MRC Building, Newcastle General Hospital, Newcastle-upon-TyneNE4 6BE, United Kingdom
Ian McKeith*
Affiliation:
Wolfson Research Unit, Institute for Aging and Health, Newcastle General Hospital, Newcastle-upon-TyneNE4 6BE, United Kingdom

Abstract

As many as two million people in the United Kingdom repeatedly see people, animals, and objects that have no objective reality. Hallucinations on the border of sleep, dementing illnesses, delirium, eye disease, and schizophrenia account for 90% of these. The remainder have rarer disorders. We review existing models of recurrent complex visual hallucinations (RCVH) in the awake person, including cortical irritation, cortical hyperexcitability and cortical release, top-down activation, misperception, dream intrusion, and interactive models. We provide evidence that these can neither fully account for the phenomenology of RCVH, nor for variations in the frequency of RCVH in different disorders. We propose a novel Perception and Attention Deficit (PAD) model for RCVH. A combination of impaired attentional binding and poor sensory activation of a correct proto-object, in conjunction with a relatively intact scene representation, bias perception to allow the intrusion of a hallucinatory proto-object into a scene perception. Incorporation of this image into a context-specific hallucinatory scene representation accounts for repetitive hallucinations. We suggest that these impairments are underpinned by disturbances in a lateral frontal cortex–ventral visual stream system. We show how the frequency of RCVH in different diseases is related to the coexistence of attentional and visual perceptual impairments; how attentional and perceptual processes can account for their phenomenology; and that diseases and other states with high rates of RCVH have cholinergic dysfunction in both frontal cortex and the ventral visual stream. Several tests of the model are indicated, together with a number of treatment options that it generates.

Type
Research Article
Copyright
Copyright © Cambridge University Press 2005

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Notes

1. The term Charles Bonnet syndrome has been variously used to describe isolated complex visual hallucinations and visual hallucinations accompanied by a range of other phenomena (Menon et al. 2003). Because of this range of uses and because there is no evidence that either definition describes a different subjective experience, we will not use it ourselves.

2. We use the term object perception in this context to include not only the perception of inanimate and animate objects but also people, faces, and animals.