Objective: Investigating the visual causality perception in Parkinson’s disease (PD) patients and comparing their performance with that of healthy individuals.

Background: Parkinson’s disease (PD) is a multifaceted neurological condition characterized by a variety of both motor and non-motor symptoms (1). Causality perception, a cognitive process involving the interpretation of events and the determination of cause-and-effect relationships(2) is particularly significant in PD since it has the potential to impact cognitive functions (3). The cognitive impairments associated with PD can influence higher-order cognitive processes, which may affect the ability to accurately perceive causality (4). The current study explored the alteration of the visual causality perception in PD patients.

Method:

Eighteen PD patients and an equal number of healthy controls completed a causality perception task. The task involved observing a pair of black balls on a grey background. In each trial, the first ball moved across the screen and contacted the second ball with varying degrees of overlap, after which the second ball started to move. Participants had to determine if they perceived a causal event (first ball caused the second ball to move) or a non-causal event (first ball passed through the second ball without affecting it). Increased overlap has been shown to shift perception from causal to non-causal.

Results:

We collected the percentage of causal reports across different degrees of ball overlap, obtaining psychometric functions from the two group. Comparing the psychometric functions across the two groups showed that the psychometric curve of PD patients had a smaller range (p<0.05) and a shallower curve (p<0.05) compared to controls, while the shift of the curve was similar across groups (p>0.05).

Conclusion: Together, these results show weaker performance in PD patients when judging perceptual causality. This effect could be related to their impaired discriminability as a result of their sensory perception impairment. Previous studies have shown that PD patients have degrees of difficulty in individuating overlapping objects (5) as well as impairments in motion perception(6). Both these factors play a role in the perceptual causality task reported here. Our results suggest that basic perceptual deficits in PD could result in difficulties in their understanding of causal relationships.

References: 1. Rana AQ, Ahmed US, Chaudry ZM, Vasan S. Parkinson’s disease: a review of non-motor symptoms. Expert review of neurotherapeutics. 2015;15(5):549-62.
2. Zhou J, Huang X, Jin X, Liang J, Shui R, Shen M. Perceived causalities of physical events are influenced by social cues. Journal of experimental psychology: human perception and performance. 2012;38(6):1465.
3. Eccles FJ, Murray C, Simpson J. Perceptions of cause and control in people with Parkinson’s disease. Disability and Rehabilitation. 2011;33(15-16):1409-20.
4. Danks D. The psychology of causal perception and reasoning. 2009.
5. Ishioka T, Hirayama K, Hosokai Y, Takeda A, Suzuki K, Nishio Y, et al. Illusory misidentifications and cortical hypometabolism in Parkinson’s disease. Movement Disorders. 2011;26(5):837-43.
6. Weil RS, Schrag AE, Warren JD, Crutch SJ, Lees AJ, Morris HR. Visual dysfunction in Parkinson’s disease. Brain. 2016;139(11):2827-43.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-impact-of-parkinsons-disease-on-causal-perception/