Objective: The objective of this study is to investigate the relationship between action verbal fluency (the capacity to name as many action words as possible in a given period of time) and executive functions using task-based fMRI.

Background: Patients with Parkinson’s disease (PD) present verbal fluency impairments even in the absence of dementia. These impairments are related to executive deficits [1]. Studies also show that PD patients present a disadvantage for the processing of words with a rich semantic motor content, such as action words, compared to other types of words. For these reasons, action verbal fluency would be particularly demanding for PD patients and would constitute a sensitive measure of cognitive deficit in PD.  However, action verbal fluency’s dependency on the cognitive fronto-striatal regions involved in executive processes still need to be clarified.

Methods: 15 non-demented patients with idiopathic PD and 15 controls without PD matched for age, education and global cognition were recruited for this study. They completed a full neuropsychological battery, including action verbal fluency. Participants also performed a modified version of the Wisconsin Card Sorting Task (WCST) [2] during three 8 min. task-based T2*BOLD fMRI sessions acquired on a 3T GE MRI scanner. The WCST is a card-sorting task that requires shifting between rules. It was shown to be associated with fronto-striatal activation. fMRI data pre-processing and GLM analysis was done in FSL.

Results: PD patients had a significantly lower performance than controls on the action verbal fluency task. There was a significant positive correlation between action verbal fluency and the performance on the WCST when all participants were included in the analysis. In the PD group, the performance in action verbal fluency was significantly correlated with regions usually associated with the planning of a set-shift, such as the anterior cingulate gyrus, ventrolateral pre-frontal cortex (PFC), dorsolateral PFC and caudate nucleus [2]. These correlations were not observed in the control group.

Conclusions: The results provide evidence that in PD, action verbal fluency is strongly reliant on executive processes. Furthermore, it indicates that action verbal fluency performance is dependent on the functional integrity of the cognitive cortico-striatal loop in PD.

References: [1] Henry, J. D., & Crawford, J. R. (2004). Verbal fluency deficits in Parkinson’s disease: A meta-analysis. Journal of the International Neuropsychological Society, 10, 608–622.

[2] Monchi, O., Petrides, M., Petre, V., Worsley, K., & Dagher, A. (2001). Wisconsin Card Sorting revisited: Distinct neural circuits participating in different stages of the task identified by event-related functional magnetic resonance imaging. The Journal of Neuroscience, 21, 7733-7741.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/action-verbal-fluency-is-related-to-the-functional-integrity-of-the-cognitive-cortico-striatal-loop-in-parkinsons-disease/