Objective: Evaluate the changes in brain connectivity between Parkinson’s disease (PD) with and without mild cognitive impairment (MCI).

Background: Up to 40% of PD patients have MCI early in the disease. Previous studies showed extensive structural and functional brain changes associated with cognitive performance in PD patients. By analyzing the MCI-non-PD patients we can distinguish better the patterns specifically associated with cognitive deficits in PD

Methods: We analyzed the connectivity patterns in 17 PDN, 19 PD-MCI, 13 MCI-nonPD patients and 27 healthy volunteers (HV) using the bootstrap analysis of stable cluster method to mathematically compute the regions of interest (ROI) in the brain. We concentrated only on the frontal cognitive regions (dorsolateral (DLPFC), ventrolateral (VLPFC) and ventromedial (VMPFC) prefrontal cortices) All participants underwent a neuropsychological assessment based on the level II MDS-Task Force criteria for MCI in PD and the MCI criteria for assessing Alzheimer’s disease. ROIs were selected in data-driven way across different cluster resolutions. The strength of the connectivity between all the ROIs were compared across groups.

Results: PDN had increased connectivity compared with HV and PD-MCI between the VMPFC-supplementary motor area (SMA), VMPFC-motor regions as well as DLPFC-superior temporal gyrus and DLPFC –hippocampus, at resolutions 19 and 180. MCI-nonPD showed the same patterns with decreased connectivity compared to PDN and HV in the VMPFC-motor, DLPFC-superior temporal connections, but not in the VMPFC-SMA pathway. PDN vs. HV had increased VMPFC-posterior cingulate connectivity at resolution 180. PD-MCI vs. HV showed increased connectivity between VLPFC-caudate nucleus and VLPFC-posterior cingulate regions, and decreased connectivity between right and left VLPFCs at resolution 180.

Conclusions: Our data reveal a significant increase in connectivity between DLPFC, VMPFC in PDN compared to HV and a significant decrease in PD-MCI patients compared to PDN. These patterns might reflect a compensational effect in PDN patients, which allows them to have a cognitive performance at the same level as healthy individuals. In the PD-MCI patients this compensational mechanism is weakened. Finally, the results indicate that the integrity of the functional connection between VMPFC and SMA is more crucial for the maintenance of cognitive function in PD than in non-PD individuals.

References: [1] Hanganu A, et al. Brain 2014; 137: 1120-9;

[4] Tam A, et al. Frontiers in aging neuroscience 2015; 7;
 

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MDS Abstracts - https://www.mdsabstracts.org/abstract/connectivity-patterns-in-frontal-cognitive-regions-in-parkinsons-disease/