Objective: Using resting-state functional MRI (rsfMRI) data of younger and older healthy volunteers and patients with Parkinson’s disease (PD) with and without mild cognitive impairment (MCI) and applying graph theory approach, we investigated the effects of age, pathology, and cognition on brain connectivity.

Background: Aging is a risk factor for MCI and the strongest predictive factor of dementia in PD patients [1, 2].  Untangling the effect of the neuro-degeneration of PD from the effects of regular aging is important for further understanding the functional connectivity in PD patients associated with cognitive deficits.

Method: Participants: PD with MCI (PD-MCI; n = 15, mean age = 69.4 ), PD without MCI (PD-nonMCI, n = 20, mean age = 63.8). Older volunteers (OHV, n = 20, mean age = 70.0). Younger volunteers (n = 30, mean age 23.8). Methods: All the participants underwent resting state fMRI (rsfMRI).  In graph theory analysis, degree is the number of connections attached to a given node in a designed binary graphed brain network [3], and hubs are nodes with high degree.  Using 118 clusters in the brain, obtained from bootstrap analysis of stable cluster (BASC) method [4], we investigate the impact of aging, disease, and cognitive state on the hub function, measured by degrees, in the brain.

Results: We observed decreased hub function (measured by degree and betweenness centrality) mainly in the medial prefrontal cortex (mPFC) in older healthy volunteers compared with younger healthy volunteers. We also found increased hub function in the posterior medial structure (precuneus and the cingulate cortex) in PD-nonMCI patients compared with older healthy volunteers and PD-MCI patients.  Hub function in these posterior medial structures was positively correlated with cognitive function in all PD patients.  These observation was survived when age as a covariate.

Conclusion: The medial structures, including the mPFC and the posterior medial cortex, are considered as core structure in the human brain [5].  Together these data suggest that the increased hub function in the posterior medial cortex could support cognition in PD patients, and that the overlapping patterns of hub modifications could mediate the effect of age as a risk factor a for cognitive decline in PD, including age-related reduction of hub function in the mPFC.

References: [1] Aarsland D, et al, 2010. Mild cognitive impairment in Parkinson disease: a multicenter pooled analysis. [2] Aarsland D, et al, 2010. The epidemiology of dementia associated with Parkinson disease. [3] Sporns O, et al, 2007. Identification and classification of hubs in brain networks. [4] Bellec P, et al. 2010. Multi-level bootstrap analysis of stable clusters in resting-state fMRI. [5] Hagmann P, et al. 2008. Mapping the structural core of human cerebral cortex.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/increased-hub-function-in-posterior-medial-cortex-in-parkinsons-disease-without-mild-cognitive-impairement-a-resting-state-fmri-study/