Motor Ability Relates to Word-Finding in Both Individuals With and Without Parkinson’s Disease

Parkinson’s disease (PD) is characterised by motor symptoms and cognitive deficits, including action language difficulties linked to disruptions of the frontostriatal brain pathway. Only a few studies have differentiated between the body parts and the amount of physical activity associated with a word (i.e., actionality) when investigating action language in PD. Additionally, an engaging lifestyle contributing to higher Cognitive Reserve (CR) may mitigate cognitive decline in PD, but its impact on action language impairments is unclear. This study aimed to investigate upper-limb action-word finding abilities in individuals with and without PD, considering word actionality and the impact of CR. Forty native-British speakers with idiopathic PD and forty matched older adults without PD participated. Action-word finding was assessed via picture-naming and verbal fluency tasks. Upper-limb motor ability was assessed through a keyboard-tapping task. CR was measured through years of education, occupational attainment, and questionnaires concerning the frequency of engagement in cognitive, leisure, and physical activities. Linear mixed-effects models demonstrated that in both groups, participants with better motor ability named pictures faster. Multiple linear regression revealed a similar relationship between motor ability and the number of generated words on the verbal fluency task. Thus, across both groups, motor ability predicted faster naming and greater fluency, suggesting shared neuronal motor–language circuitry. No reliable PD-specific deficit for upper-limb action words was observed under medication and current task demands. CR showed minimal influence, with only a weak effect on picture naming accuracy. The relationship between motor and action word-finding abilities is discussed.