Objective: Hallucination is a common feature in patients with advanced Parkinson’s disease(PD) and dementia with Lewy bodies (DLB).

Background: The pareidolia test is a tool that evokes visual hallucination-like illusions, and these illusions may be a surrogate marker of visual hallucinations in DLB and PD.In the current study we examined the differences between PD, DLB and Alzheimer’s disease (AD) patients using the pareidolia test.

Methods: There were 63 subjects including 21 DLB patients, 20 PD patients and 22 AD patients. We conducted the noise pareidolia test and MMSE, ADAS-Jcog for each subject. The noise pareidolia test contained 40 black and white images that consist of visual noise with a spatial frequency of 1/f3. Black and white images of human faces were embedded in 8 of the 40 images. Subjects were requested to state whether a face was present and point to the place where they observed a face. Each picture was presented for a maximum of 30 seconds. The responses were classified into three types: (1) illusory responses, in which subjects falsely found faces in images without a face, (2) detection misses, in which subjects did not detect the embedded faces and (3) correct responses, in which subjects correctly responded “nothing exists” or correctly detected the embedded image. The number of images in which subjects made illusory responses was used as a measure of pareidolic illusions. Intergroup comparisons were performed using the Kruskal-Wallis test.

Results: Intergroup comparisons revealed the main effect was significant in all items in the noise pareidolia test. The mean numbers of illusory responses in the noise pareidolia test were 4.29 (8.74) for DLB, 0.75 (1.68) for PD and 0.32 (0.78) for AD. The DLB group produced more illusory responses than the AD group and PD group. The numbers of correct responses were 34.8 (8.74) for DLB, 38.70 (2.36) for PD and 39.64 (2.5) for AD. DLB group produced less correct responses than the AD group and PD group. The numbers of detection misses were 1.62 (2.62) for DLB, 0.55 (1.23) for PD and 0.05 (0.21) for AD. DLB group produced more detection misses than the AD group and PD group.

Conclusions: Patients with DLB are more likely to develop paleridia, even when compared with PD patients and AD patients with the same level of cognitive function. This finding is an effective means for predicting the appearance of hallucinations in Lewy body disease.

References: Uchiyama M, Nishio Y, Yokoi K, Hirayama K, Imamura T, et al. (2012) Pareidolias: complex visual illusions in dementia with Lewy bodies. Brain 135: 2458–2469.

Yokoi K, Nishio Y, Uchiyama M, Shimomura T, Iizuka O, et al. (2014) Hallucinators find meaning in noises: eidolic illusions in dementia with Lewy bodies. Neuropsychologia 56: 245–254.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/defective-visual-perception-in-patients-with-lewy-body-disease-assessment-of-hallucinations-with-pareidolia-test/