Face Pareidolia : Visual illusion and Minor Hallucination in in Parkinsonʼs Disease

Abstract

  Pareidolia is a visual illusion in which meaningful figures (faces, humans, or animals, etc.) are found in ambiguous objects. While pareidolia is experienced by healthy persons, it is frequently observed in patients with Parkinsonʼs disease (PD) and is associated with subsequent cognitive dysfunction. Our resting-state functional MRI study revealed that PD patients with face pareidolia show decreased functional connectivity between the medial prefrontal cortex and fusiform gyrus compared with those without pareidolia. By using simultaneous eye-tracking and electroencephalography recording, we also found that PD patients with face pareidolia show increased activation in frontal electrodes during the pareidolia task, and the frontal brain network was altered immediately before the pareidolic reactions. Taken together, the alteration of the frontal-temporal network is suggested to play an important role in the pathological face pareidolia in PD. On the other hand, previous SPECT studies have indicated the reduced occipital blood flow in PD patients with pareidolia. We suggest that face pareidolia in PD might be related to two major mechanisms: frontal “top-down” attentional regulation and occipital “bottom-up” visual information. Visual illusions and hallucinations in PD are complex phenomena involving widespread brain activities, and further studies, including functional brain imaging, are expected to elucidate the functional and pathological background.