Functional connectivity in neurologically healthy aging and Parkinson's Disease: Investigating the role of age and medication

Both aging and Parkinson's disease (PD) are associated with cognitive decline. Although electroencephalography (EEG) has been used to study cognitive function, few studies have examined how aging and PD affect brain network efficiency (functional connectivity) during a digit vigilance task, which primarily assesses sustained attention with moderate executive demands. Moreover, the influence of dopaminergic medication on functional connectivity during cognitive engagement remains unclear. Therefore, this study investigated the effects of age, PD, and dopaminergic medication on EEG-derived functional connectivity during a digit vigilance task. Twenty-one individuals with PD (Hoehn & Yahr I-III, ON levodopa, with 19 tested ON/OFF medication) and 87 healthy controls (aged 20-75) participated in this study. Participants underwent cognitive assessment and performed a digit vigilance task while seated. Concomitantly, data from a 32-channel EEG (500 Hz) system was acquired, preprocessed and analyzed for functional connectivity across five cortical regions (frontal, central, parietal, temporal, and occipital). Healthy controls exhibited age-related declines in cognitive performance and frontal functional connectivity, particularly at the age of 70-75 years. Compared to age-matched healthy controls, people with PD (pwPD) showed impaired cognitive performance, alongside reduced central functional connectivity. No significant differences in functional connectivity were found between ON and OFF states. Therefore, during an executive function task, healthy individuals exhibit age-related declines in the frontal functional connectivity, mainly in the 70s. For pwPD, deficits in functional connectivity were also observed in the central area, with no effect promoted by dopaminergic medication. Findings highlight the importance of targeted rehabilitation strategies for these regions in preserving cognitive-motor integration and improving functional outcomes.