Affective theory of mind in Parkinson's disease: the effect of cognitive performance

Among other non-motor symptoms, theory of mind (ToM), the ability to recognize, understand and infer others' mental states, beliefs, intents and wishes, has been shown to deteriorate during the course of Parkinson's disease (PD). It has been speculated that ToM impairments could be related to cognitive deficits in PD. However, the current state of literature suggests that there is heterogeneity regarding the involvement of cognitive functioning in the relationship of PD and ToM. The study aimed to measure affective ToM abilities and cognitive performance in a sample of PD patients, to explore the link between affective ToM abilities and cognitive status, and to examine the impact of PD on affective ToM through the mediator effect of cognitive performance.

Sixty-five patients diagnosed with idiopathic PD and 51 healthy controls matched for age, gender and educational level completed a visual affective ToM task (Reading the Mind in the Eyes - RMET), cognitive performance was evaluated with Montreal Cognitive Assessment, and psychiatric symptoms were measured with BPRS-E (Brief Psychiatric Rating Scale).

Affective ToM abilities were preserved in early PD patients, declining as the disease progressed. Deficits in cognitive functioning predicted deficiencies in affective ToM. Although attention (AT), executive functions (EF) and visuospatial abilities (VSA) together mediated the relationship between PD and affective ToM, only VSA impairment had a specific negative impact on affective ToM. Moreover, 41% of the total effect of attention and executive functions on affective ToM was mediated by visuospatial skills.

Cognitive performance may have an impact on the relationship between PD and affective ToM through the involvement of VSA. The influence of AT and EF in this relationship appears to be also exerted by PD patients' VSA.