Cortical activation and functional connectivity between healthy elderly and Parkinson’s disease patients and between cognitive subgroups of Parkinson’s patients: a multichannel functional near-infrared spectroscopy study

Background: The rising global burden of Parkinson's disease (PD) is often related to cognitive decline. Exploring neuroimaging biomarkers is crucial for early diagnosis. Methods: The purpose of the exploratory research was to look at the differences in cortical activation and functional connectivity between PD patients and healthy controls (HC), as well as among cognitive subgroups of PD, using multichannel functional near-infrared spectroscopy (fNIRS) during a verbal fluency task. A total of 39 PD patients and 20 age-matched HC were assessed. Results: Results showed significantly reduced oxygenated hemoglobin (oxy-Hb) concentrations in PD patients, particularly in the right temporal lobe, compared to HC. Among PD cognitive subgroups, patients with Parkinson's disease dementia (PDD) displayed notably lower oxy-Hb levels in key brain regions compared to PD with normal cognition (PD-NC) and PD with mild cognitive impairment (PD-MCI). The analysis among the four groups showed that the HC group and the PDD group had the most differences in activation. Functional connectivity analyses between PD subgroups revealed that PD-NC patients had stronger connectivity between prefrontal regions than PD-MCI and PDD groups. Conclusion: Our findings generate the hypothesis that PD is associated with altered neurovascular responses and disrupted cortical network organization in the frontal and temporal lobes, especially in cognitively impaired subgroups. These results support the potential utility of fNIRS for characterizing cognition-related neural alterations in PD and provide a basis for future hypothesis-driven and longitudinal investigations.