Individuals with Parkinson's disease typically develop a range of cognitive impairments early in the disease progression, with executive function being one of the first processes to decline. In discourse (units of language longer than one sentence), these abilities appear to be crucial for coherence, a concept signifying the relatedness of communication structures. Coherence can be divided into two conceptual levels: global coherence, which represents the degree to which each communication unit relates to the overall topic; and local coherence, which represents the degree to which each communication unit relates to the unit directly preceding it. It follows that high levels of coherence, which require discourse structures to “interact” and connect thematically with each other, should be related to high levels of executive function. However, studies on the precise relationships between coherence types and executive function have yielded unclear conclusions.
This poster investigates the comparative levels of global and local coherence in participants with Parkinson's disease. Using retrospective data from Wilson's (2013) dissertation, we are analyzing the discourse of participants who either spoke on a topic while sitting (single task) or while peddling a stationary bicycle (dual task). These discourse samples are analyzed using a four-point coherence ranking scale. Scores of global coherence and local coherence are compared in single and dual task conditions. Additionally, correlations between coherence types and executive function are reported. These results may shed more light into the relationships among global coherence, local coherence, and executive function in patients with Parkinson's disease.