Pareidolia as a diagnostic and prognostic marker in Lewy body disease

Background: Pareidolia refers to complex visual illusions in which ambiguous and visually noisy stimuli are perceived as meaningful forms. The presence and severity of pareidolia may be prodromal indicators of visual hallucinations and could aid in the diagnosis of Dementia with Lewy Bodies (DLB). In this study, we explored the potential of pareidolia as a diagnostic marker for prodromal DLB (MCI-LB), compared to DLB and Alzheimer’s disease (AD), and examined its association with cognitive deficits and clinical features. Methods: 81 participants were assessed: 40 DLB/MCI-LB patients (18 DLB, 22 MCI-LB), 21 AD patients, and 20 healthy controls. Global cognitive functioning was evaluated using the Montreal Cognitive Assessment (MoCA). Pareidolia was measured with two tests: the Scenery Pareidolia Test and the Noise Pareidolia Test. Results: Mean age was comparable across groups: DLB (77.5 ± 7.12 years), MCI-LB (75.32 ± 6.65), AD (74.91 ± 8.49), and controls (73.05 ± 9.29). MoCA scores were: DLB (15.0 ± 5.25), MCI-LB (21.68 ± 3.56), AD (17.86 ± 4.36), and controls (23.55 ± 3.33). Both DLB and MCI-LB patients showed significantly more pareidolic responses than controls (DLB: p < 0.001; MCI-LB: p = 0.001). The DLB group performed worse than the AD group on both pareidolia tests (Scenery: p = 0.002; Noise: p < 0.001), while MCI-LB patients differed from AD only on the Noise test (p = 0.03). Pareidolic responses were more frequent in DLB/MCI-LB patients reporting minor hallucinatory phenomena (e.g., feeling of presence or passage, p = 0.04), though not associated with fully formed visual hallucinations. Illusory responses in DLB patients correlated negatively with global cognition (r = -0,53, p = 0.012) and visuospatial abilities (r = -0,49, p = 0.03). Conclusion: These results support the utility of pareidolia as a potential cognitive marker for prodromal DLB. Furthermore, pareidolia appears to be associated with visuospatial deficits and minor hallucinatory experiences. Ongoing research will explore its prognostic value for the development of visual hallucinations.