Objective: The study aimed to investigate apathy subdomains (reward deficiency syndrome, emotional distress, executive function, auto-activation deficit) and cognitive executive functions differences between PD patients with preserved or impaired theory of mind (ToM), and to explore the impact of apathy subdomains and cognitive executive functions on ToM in PD.

Background: Emerging evidence suggests that ToM is impaired in PD patients. This impairment in ToM in PD may be at least partly attributable to cognitive executive dysfunction. However, very little is known about the impact of different subdomains of apathy on ToM in PD.

Method: Twenty-six PD patients underwent a neuropsychological and clinical assessment investigating ToM (Happe’s Strange Stories Test), executive functions (Modified Wisconsin Card Sorting Test and Calibrated Ideational Fluency Assessment – semantic), and apathy symptoms (Lille Apathy Rating Scale). Mann-Whitney Test and Chi-Square Test was used to assess between-groups differences in demographic or clinical data. Multivariate Analysis of Covariance using bootstrapping and Bonferroni correction was performed including age as covariate. Regression analysis was used to explore the relationship between ToM, executive functions, and apathy subdomains in PD with impaired or preserved ToM.

Results: Two groups were created based on the ToM impairment, impaired ToM (n=12) and preserved ToM (n=14). Impaired ToM group showed significant lower scores in executive functions and affective-emotion apathy compared to preserved ToM group. Specifically, differences in semantic verbal fluency [F(1,22)=6.65; p=.017, partial eta squared=.23], motivation subdomain of apathy [F(1,22)=12.37; p=.002, partial eta squared=.36], and emotional response subdomain of apathy [F(1,22)=5.10; p=.034, partial eta squared=.19] were found. In impaired ToM group, emotional response was significant explaining 43% of the variance in ToM [F(1,10)=9.43; p=.012]. Motivation and semantic verbal fluency failed to add significantly to the model. No regression was found in preserved ToM group.

Conclusion: Findings suggest that impaired performance in ToM is explained by deficits in affective-emotion apathy in PD patients. ToM impairment is not only associated with cognitive executive dysfunction in PD. Therefore, treatments that combine rehabilitation of cognitive impairment and clinical symptoms are necessary in PD patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/influence-of-emotion-affective-apathy-in-theory-of-mind-in-parkinsons-disease-patients/