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Neuropsychologia. 2014 Apr;56:245-54. doi: 10.1016/j.neuropsychologia.2014.01.017. Epub 2014 Jan 31.

Hallucinators find meaning in noises: pareidolic illusions in dementia with Lewy bodies.

Author information

1
Department of Behavioural Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan.
2
Department of Behavioural Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan. Electronic address: nishiou@med.tohoku.ac.jp.
3
Department of Speech, Language and Hearing Sciences, Niigata University of Health and Welfare, 1398 Shimami-cho, Kita-ku, Niigata 950-3198, Japan.
4
Department of Rehabilitation Medicine, Akita Prefectural Centre of Rehabilitation and Psychiatric Medicine, 352 Kyowakamiyodokawa, Daisen 019-2413, Japan.

Abstract

By definition, visual illusions and hallucinations differ in whether the perceived objects exist in reality. A recent study challenged this dichotomy, in which pareidolias, a type of complex visual illusion involving ambiguous forms being perceived as meaningful objects, are very common and phenomenologically similar to visual hallucinations in dementia with Lewy bodies (DLB). We hypothesise that a common psychological mechanism exists between pareidolias and visual hallucinations in DLB that confers meaning upon meaningless visual information. Furthermore, we believe that these two types of visual misperceptions have a common underlying neural mechanism, namely, cholinergic insufficiency. The current study investigated pareidolic illusions using meaningless visual noise stimuli (the noise pareidolia test) in 34 patients with DLB, 34 patients with Alzheimer׳s disease and 28 healthy controls. Fifteen patients with DLB were administered the noise pareidolia test twice, before and after donepezil treatment. Three major findings were discovered: (1) DLB patients saw meaningful illusory images (pareidolias) in meaningless visual stimuli, (2) the number of pareidolic responses correlated with the severity of visual hallucinations, and (3) cholinergic enhancement reduced both the number of pareidolias and the severity of visual hallucinations in patients with DLB. These findings suggest that a common underlying psychological and neural mechanism exists between pareidolias and visual hallucinations in DLB.

KEYWORDS:

Acetylcholine; Dementia with Lewy bodies; Pareidolias; Visual hallucinations; Visual illusions

[Indexed for MEDLINE]

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