Objective: The aim of this study is to investigate the correlation between the number of illusory responses on the Pareidolia test and cerebral perfusion in Parkinson’s disease (PD) without dementia (PDwoD).

Background: Pareidolia is observed as visual illusion in patients with dementia with Lewy bodies. It was reported that the correlations between pareidolic illusions and hypometabolism measured by 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) were seen in the bilateral temporal, parietal and occipital cortexes in PD patients without dementia [1]. However, the association between the cerebral perfusion and Pareidolia is poorly documented.

Method: We enrolled 57 PDwoD patients (69.9±8.7 years old, 27 females). The Pareidolia test and other neuropsychological tests were undertaken. We estimated cerebral perfusion using 99mTc-ethyl cysteinate dimer single photon emission computed tomography (99mTc-ECD SPECT). Z-scores of hypoperfusion were calculated using easy Z-score imaging system (eZIS), while the perfusion images were standardized by SPM2. We assessed the values of extent and severity by Z-scores of hypoperfusion in the segmented sites according to the Talairach level 3 template using a voxel-based stereotactic extraction estimation (vbSEE). The extent and severity values mean as the ratio of voxels with a Z-score > 2.0 and average degree of voxels with a Z-score > 2.0 in each of the volumes of interest, respectively. Statistical analysis was performed by JMP version 11.

Results: There were significant correlations between the number of pareidolic illusions and the extent of cerebral hypoperfusion in the areas of right anterior cingulate, right inferior frontal, left medial frontal and bilateral orbital gyrus (p<0.05). In these areas, the severity of hypoperfusion was correlated with the number of pareidolic illusions only in the left orbital gyrus area (p<0.05).

Conclusion: Our results suggest that pareidolic illusions were associated with decreased cerebral perfusion in inferior and medial side of frontal lobe of the brain in the PDwoD patients. And it is conceivable that the extent of cerebral hypoperfusion is more contribute to pareidolic illusions than the severity. The results of our study may also help to explain that pareidolic illusions evoked by the Pareidolia test is account for mild frontal lobe dysfunction in PDwoD.

References: 1. Uchiyama M, Nishio Y, Yokoi K. Pareidolia in Parkinson’s disease without dementia: A positron emission tomography study. Park Relat Disord. 2015;21(6):603-609. doi:10.1016/j.parkreldis.2015.03.020

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MDS Abstracts - https://www.mdsabstracts.org/abstract/correlation-between-pareidolia-and-cerebral-perfusion-by-spect-in-parkinsons-disease-without-dementia-a-retrospective-study/