Biased numerical cognition impairs economic decision‐making in Parkinson's disease

Abstract

ObjectivePrevious findings suggest a context‐dependent bihemispheric allocation of numerical magnitude. Accordingly, we predicted that lateralized motor symptoms in Parkinson's disease (PD), which reflect hemispheric asymmetries, would induce systematic lateralized biases in numerical cognition and have a subsequent influence on decision‐making.MethodsIn 20 PD patients and matched healthy controls we assessed numerical cognition using a number‐pair bisection and random number generation task. Decision‐making was assessed using both the dictator game and a validated questionnaire.Results PD patients with predominant right‐sided motor symptoms exhibited pathological biases toward smaller numerical magnitudes and formulated less favorable prosocial choices during a neuroeconomics task (i.e., dictator game). Conversely, patients with left‐sided motor symptoms exhibited pathological biases toward larger numerical magnitudes and formulated more generous prosocial choices. Our account of context‐dependent hemispheric allocation of numerical magnitude in PD was corroborated by applying our data to a pre‐existing computational model and observing significant concordance. Notably, both numerical biasing and impaired decision‐making were correlated with motor asymmetry.InterpretationAccordingly, motor asymmetry and functional impairment of cognitive processes in PD can be functionally intertwined. To conclude, our findings demonstrate context‐dependent hemispheric allocation and encoding of numerical magnitude in PD and how biases in numerical magnitude allocation in Parkinsonian patients can correspondingly impair economic decision‐making.

Altruism in Parkinson’s disease.

“…One important distinction between studies is that we administered only one trial on the stranger version, while Arshad et al had 20, therefore more trials may be necessary to get a clearer picture of the role that hemispheric asymmetries play in common economic games. Nevertheless, it is interesting that left-sided patients show this increase in prosociality both in the altruistic intertemporal choice tasks (implicit) in the present study and in the stranger version of the dictator game in the study by Arshad et al (2017). The underlying mechanism for this hemispheric asymmetry is unclear.…”

“…The underlying mechanism for this hemispheric asymmetry is unclear. Arshad et al (2017) suggested that this effect was due to biased numerical cognition, but this should have resulted in group differences in all conditions of the intertemporal choice task and the dictator game. Furthermore, while some evidence supports greater involvement of the right hemisphere in various prosocial tasks (Hare et al, 2010; Morishima et al, 2012), a recent meta-analysis of fMRI studies reported bilateral involvement (Cutler & Campbell-Meiklejohn, 2019).…”

“…Our secondary aim is to explore the relationships between our altruism measures and patient characteristics thought to contribute to reward-based decision-making and prosociality, including whether they take dopamine agonist medications, whether they demonstrate evidence of cortico-striatal cognitive dysfunction as suggested by a diagnosis of PD-related mild cognitive impairment (PD-MCI), and whether they have greater left versus right hemispheric compromise as indicated by the side of motor symptom onset. The laterality question was included based on prior reports of greater prosociality in the dictator game among left-sided onset patients relative to right-sided patients (Arshad et al, 2017). This document is copyrighted by the American Psychological Association or one of its allied publishers.…”

“…However, whether patients acted more generously or egoistically depended on the laterality of their hemispheric compromise as inferred from the severity of lateralized motor symptoms. Specifically, relative to controls, patients with greater right hemisphere compromise (more severe left-sided motor symptoms) gave more to the stranger, and patients with greater left hemisphere compromise (right-sided symptoms) kept more money for themselves (Arshad et al, 2017).…”