Impairment in Theory of Mind in Parkinson’s Disease Is Explained by Deficits in Inhibition

Abstract

Objective. Several studies have reported that people with Parkinson’s disease (PD) perform poorly on tests of ‘Theory of Mind’ (ToM), suggesting impairment in the ability to understand and infer other people’s thoughts and feelings. However, few studies have sought to separate the processes involved in social reasoning from those involved in managing the inhibitory demands on these tests. In this study, we investigated the contribution of inhibition to ToM performance in PD. Methods. 18 PD patients and 22 age-matched healthy controls performed a ToM test that separates the ability to infer someone else’s perspective from the ability to inhibit one’s own. Participants also completed a battery of standard measures of social and executive functioning, including measures of inhibition. Results. The PD patients performed worse on the ToM test only when the inhibitory demands were high. When the level of inhibition required was reduced, there were no significant group differences. Furthermore, executive impairments in PD patients were limited to measures of inhibition, with disadvantages associated with poorer ToM performance in this group. Conclusions. This study provides convincing evidence that the apparent impairment observed on ToM tests in PD is explained by deficits in inhibition.

Social cognition in cervical dystonia: phenotype and relationship to anxiety and depression

“…Although executive abilities were not directly measured, executive dysfunction is common in idiopathic dystonia [29], and may partly explain our participants' poorer performance on the ToM reality-known task. In Parkinson's disease patients, performance on a ToM task worsened when self-perspective inhibitory demands were high, in association with executive control measures [30]. Future , the model statistic reported is chi-squared and the predictor b is the exponentiation of the b coefficient, which can be interpreted as an odds ratio.…”

Social Cognition in Patients with Early-Onset Parkinson’s Disease

“…Several studies have linked performance of PD patients on affective ToM tasks with other cognitive deficiencies, including visuospatial ability, inhibition, cognitive flexibility, and working memory [ 23 , 27 , 75 ]. Although we found that differences in ToM performance between EOPD and controls were not mediated by overall cognitive ability, deficiencies in specific cognitive domains could have impacted performance in our patients.…”

“…More recent studies have centered on the same SC domains [ 23 , 24 ]. Their findings demonstrate consistent deficits in ToM, especially cognitive ToM [ 23 , 25 , 26 ], although a growing body of evidence shows that affective ToM is also compromised [ 25 , 27 , 28 ]. Furthermore, deficits in ToM appear to be present even in the early stages of the disease [ 29 ] and worsen with disease progression [ 28 ] and are not associated with dopamine-based therapy [ 26 ].…”

“…Furthermore, deficits in ToM appear to be present even in the early stages of the disease [ 29 ] and worsen with disease progression [ 28 ] and are not associated with dopamine-based therapy [ 26 ]. Although no relationships between SC deficits and general neurocognition have been found [ 30 , 31 ], there have been reports of a link between ToM and executive functions, including working memory, cognitive flexibility, and inhibition [ 23 , 27 ].…”

“…Although some studies have included a minority of patients with EOPD in their samples [ 27 , 33 , 36 , 38 ], SC has not been specifically studied in EOPD despite multiple reports indicating that this subgroup of patients perceives their quality of life and emotional wellbeing to be worse overall independent of depression status [ 39 , 40 ], report less satisfactory marital and family relationships and social life, and perceive more stigmatization [ 41 ]; these aspects could all be related to perception, processing, and responding to social stimuli. In addition, certain motor [ 42 , 43 ], cognitive [ 4 , 42 – 44 ], neurobiological [ 45 , 46 ], and genetic [ 43 ] differences have been reported between early- and late-onset PD patients; thus, it is possible that differences in SC ability are also present.…”