Objective: This study aims to investigate whether cognitive strategies on verbal fluency tasks differentiate Parkinson’s disease (PD) from Progressive Supranuclear Palsy (PSP) and healthy adults, and are associated with the progression of clinical motor symptoms in Parkinson’s disease.

Background: Cognition is involved in the voluntary control of motor behaviours, and distinct relationships are found between cognitive and motor domains in Parkinsonian syndromes. Our previous work has shown that global cognition is specifically linked with the progression of non-tremor motor symptoms (e.g., gait) in PD ​[1]​, and verbal fluency and gait variability are longitudinally associated in PSP [2]​. In this study, we analyse cognitive strategies on verbal fluency tasks to understand whether performance (i) differentiates PD from PSP and healthy adults, and (ii) is associated with the progression of clinical motor symptoms in PD.

Method: As part of the Oxford Quantification in Parkinsonism longitudinal study, we tested N = 86 participants (39 PD, 16 PSP, 31 healthy adults) over seven visits at three-month intervals. Motor symptoms were assessed using the MDS-UPDRS-III scale, and cognitive function was tested using phonemic (letter F) and semantic (animal) verbal fluency tasks. The Troyer method was applied to score cognitive strategies – clustering and switching – on fluency tasks. A linear mixed effects analysis was applied to test group differences in fluency performance and associations with motor progression.

Results: A clustering deficit on the semantic fluency task differentiates PD from healthy adults; switching on both fluency tasks is more impaired in PSP compared with PD. Longitudinally, there is a significant interaction between fluency strategies and the progression of non-tremor motor symptoms in PD.

Conclusion: Verbal fluency strategies differentiate between disease groups and are distinctly linked with the progression of non-tremor motor symptoms in PD. The application of a strategy analysis method provides deeper insight into the nature of cognitive impairment in PD and the shared disease mechanisms underlying cognitive and motor dysfunction. These findings underscore the clinical value of verbal fluency tasks for PD assessment.

References: ​​1. Gibbs MC, D’Souza A, Sotirakis C, Crawford TJ, Antoniades CA. Cognitive function is associated with the progression of non-tremor motor symptoms in Parkinson’s disease. Front Aging Neurosci 2026;18:1765860. https://doi.org/10.3389/fnagi.2026.1765860
2. D’Souza A, Sotirakis C, Conway N, FitzGerald JJ, Antoniades CA. Verbal fluency is associated with Gait impairment in Progressive Supranuclear Palsy. Clin Park Relat Disord 2025;13:100380. https://doi.org/10.1016/J.PRDOA.2025.100380

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MDS Abstracts - https://www.mdsabstracts.org/abstract/differentiation-of-parkinsonian-syndromes-using-cognitive-strategies-and-associations-with-non-tremor-motor-progression/