The effect of attentional set-shifting, working memory, and processing speed on pragmatic language functioning in Parkinson’s disease

Parkinson’s disease (PD) is traditionally associated with motor symptoms. However, impairments in language functioning may also accompany this disorder. The present study investigated pragmatic language deficits in PD and their relationship to cognitive functioning. Forty patients with PD were compared to ageand IQ-matched controls on measures of pragmatic language functioning using the Test of Language Competence Expanded (TLC-E), and measures of attentional set-shifting, working memory, and processing speed. Overall, PD patients were impaired on aspects of language, working memory, and processing speed. Measures of cognition were significantly correlated with pragmatic language functioning. Path analyses revealed that deficits in pragmatic language functioning were mediated by verbal working memory and processing speed, but not attentional set-shifting. Regression analyses found that processing speed was a stronger determiner of pragmatic language performance than verbal working memory. Results suggest that pragmatic language deficits may be explained in terms of deficits in processing speed associated with the disease.