Objective: To investigate the neural mechanism of face pareidolia in Parkinson’s disease (PD) patients using resting state functional magnetic resonance imaging (rs-fMRI).

Background: Face pareidolia is a complex visual illusion in which one perceives an ambiguous non-human object as a face. Although face pareidolia may occur in healthy subjects, previous studies reported PD patients experience it much frequently. However, neural mechanism and clinical relevance of pareidolia is unclear.

Methods: Seventy-six PD patients who admitted to Osaka University hospital from Sep. 2015 to Nov. 2016 were included to this study. All patients underwent clinical evaluations including MDS-UPDRS (part1-4), MMSE, FAB, MoCA, Benton judgement of line orientation test, and the Pareidolia test. In the Pareidolia test, patients who experienced at least one pareidolic response were considered as pareidolia-positive, and the rest were considered as pareidorlia-negative. All patients also underwent MR scans including rs-fMRI by using 3-T magnetic resonance scanner (GE Medical Systems, WI). Resting Functional connectivity analyses were performed by using the CONN-fMRI Functional Connectivity toolbox v17. Local ethical committee approved this study and written informed consent was obtained from all participants.

Results: Thirty-five patients were pareidolia-positive, and Forty-one were pareidolia-negative. Pareidolia-positives were older and worse in cognitive status than pareidolia-negatives. ROI based analysis revealed left-dominant decreased functional connectivity in bilateral fronto-parietal networks, including left frontal operculum cortex (FO) and left superior parietal lobule (SPL), bilateral superior temporal gyrus and left temporo-parietal junction (TPJ). Seed based analysis using left FO as seed also revealed the decreased connectivity between left FO and both left SPL and left TPJ.

Conclusions: Because of its importance for social activity, previous researches has emphasized the fast and sensitive nature of face-recognition network, which could lead to pareidolic reaction. Considering previous findings revealing SPL role in visual attentional control and TPJ role in detecting salient visual stimulus, our findings may suggest that top-down attentional modulation to visual processing pathway via fronto-parietal network involved in pareidolic reaction, and impaired appropriate modulation may lead to frequent face pareidolia in PD.

References: Uchiyama M. et al. Parkinsonism Relat Disord. 2015;21(6):603-9

Liu J. et al. Cortex. 2014;53:60-77

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MDS Abstracts - https://www.mdsabstracts.org/abstract/decreased-fronto-parietal-connection-is-associated-with-face-pareidolia-in-parkinsons-disease/