Coexistent impairments in executive functions and language comprehension in patients with Parkinson's disease (PD) have been repeatedly observed. In this study, the aim was to provide insights into the interaction between linguistic representation and processing and executive functioning. Therefore, sentence comprehension and executive functions were assessed in 28 Dutch-speaking PD patients and 28 healthy control subjects. Three aspects of the sentence materials were varied: (1) phrase structure complexity, (2) sentence length, and (3) picture congruence. PD patients with mild-to-moderate disease severity showed decreased sentence comprehension compared to healthy control subjects. The difficulties encountered by PD patients were not limited to one aspect of the sentence materials. The same pattern of results was present in healthy control subjects. Deficits in set-switching were specifically associated with the comprehension of passive sentences. Generally, our study confirms that there does not appear to be a language faculty encapsulated from the influence of executive functions.
A growing number of studies suggest that language problems in Parkinson’s disease (PD) are a result of executive dysfunction. To test this hypothesis we compared Dutch verb production in sentence context in a group of 28 PD patients with a control group consisting of 28 healthy participants matched for age, gender and education. All subjects were assessed on both verb production in sentence context as well as on cognitive functions relevant for sentence processing. PD patients scored lower than healthy controls on the verb production ability‐scale and showed a response pattern in which performance was worse (1) in base than in derived position; (2) in present than in past tense; (3) for intransitive than in transitive verbs. For the PD group the score on the verb production ability‐scale correlated significantly with set‐ switching and working memory. These results provide support for previous research suggesting that executive dysfunctions underlie the performance of the PD patients on verb production. It is furthermore suggested that because of failing automaticity, PD patients rely more on the cortically represented executive functions. Unfortunately, due to the disturbed intimate relation between the basal ganglia and the frontal cortex, these executive functions are also dysfunctional. Also appeared as: Colman, K.S.F., Koerts,J., van Beilen,M., Leenders,K.L., Post,W.J., & Bastiaanse,R., (2009). The impact of executive functions on verb production in patients with Parkinson's disease. Cortex 45, 930‐942. Chapter 4: Verb production in patients with Parkinson’s disease
