Fluency boost from walking in Parkinson's disease

Abstract

OBJECTIVE: Examine the impact of a motor task on verbal fluency in individuals with Parkinson’s disease (PD) Background: Dual-tasking, in which individuals engage simultaneously in motor and cognitive tasks, has long been known to impair motor performance in PD; recent evidence indicates that it also impairs cognition (set-shifting). In healthy adults without PD, motor activity can improve performance on tasks of ideational fluency. Performance on phonemic verbal fluency (VF), an executive-function task widely used in clinical evaluation and in research studies of PD, is correlated with ideational fluency in healthy young adults and in those with focal frontal-lobe lesions. VF may likewise be enhanced by motor activity, perhaps even in PD, in which both motor and executive functions are impaired. METHODS: Non-demented individuals with mild-moderate idiopathic PD (n=18, 10 men, mean age 64 [SD=10]) performed the Timed Up and Go (TUG), a brief motor task that taxes both motor and executive function. The order was single-task TUG; cognitive/motor dual-task VF/TUG; single-task VF. VF was measured in words per second (wps), calculated for single-task VF for the time the participant needed to complete the dual-task condition. Proportionate words per second (pwps) measured dual-task impact as a percentage of single-task VF. We also examined correlations between the dual-task effect and disease severity: Hoehn & Yahr stage and United Parkinson’s Disease Rating Scale (UPDRS) total score. RESULTS: Mean wps was higher for dual-task than single-task VF (t=3.5, p=.003). The size of this dual-task benefit inversely correlated with UPDRS total score (ρ=-.50, p= .03). Mean pwps also showed an advantage for dual-task VF (t=3.7, p=.002) and an inverse correlation with UPDRS total score (ρ=-.47, p=.05). CONCLUSIONS: Individuals with PD may perform better on verbal fluency when it is performed simultaneously with a motor task. A potential explanation is the reported premotor-parietal hyperconnectivity in PD that is associated with fewer motor difficulties during dual-tasking. In mild PD, this presumably compensatory connectivity may facilitate prefrontal-parietal arousal and central executive network processing, leading to improved function or regulation of attention or fluency. In later stages of PD, this compensation may decline or be insufficient to aid fluency when basal ganglia dysfunction worsens.