Objective: To unravel functional connectivity (FC) traits in Parkinson’s disease mild cognitive impairment (PD-MCI).

Background: PD-MCI is a well-known risk factor for PD associated dementia. Several FC changes have been previously reported (1). Two connectome analyses were used: Network Based analysis (NBS) and Connectome Independent Component Analysis (connICA).

Method: 23 PD-MCI patients, 21 cognitively normal PD (PDCN) patients, and 21 healthy controls (HC) were scanned in a 3T MR scanner. PD-MCI was diagnosed according to the MDS Task Force Guidelines (level II). T1-w and T2-w high resolution scans, and 10 minutes eyes-open resting state BOLD fMRI images with standard (monoband, TR=2s) and multiband (TR=800ms) images were obtained. MRI preprocessing included: T1-w parcellation into 72 cortical and 8 subcortical regions for hemisphere (Freesurfer), standard fMRI pre-processing, and nuisance regression (AFNI). Next, we computed FC matrices for multiband and monoband images for NBS (2) and connICA (3). F values were computed with mixed random effect model for each FC-trait weight to reveal significant differences between groups.

Results: Four FC-traits showed significant differences across groups (Table in [figure1]) (p ≤ 0.05/15). FC-traits 2, 6 and 9 showed significant differences in the comparisons HC vs. PDCN and HC vs. PD-MCI. In FC-trait 5 a significant effect size was found for HC vs. PD-MCI and PDCN vs PD-MCI [figure1]. FC-trait 2 encompasses the visual (VN), the sensorimotor (SMN), and the attention networks (AN). FC-trait 6 represents the connectivity of cortical structures with the thalamus. And FC-trait 9 mirrors connections of the Default Mode Network (DMN) with other cortical regions [figure2]. A unique trait (FC-trait 5) differentiates PD-MCI patients from the other groups. FC-trait 5 includes connections between the SMN, limbic networks, and, mainly the AN, whose disruptions have been previously described in PD-MCI patients. The NBS analysis showed differences among PDCN, PD-MCI, and HC in a network that resembles the combination of FC-traits 2 and 5.

Conclusion: Three independent FC-traits encompassing networks involving cognitive and motor functions were found in PD versus HC. Interestingly, a unique FC-trait encompassing the SMN, attentional networks and limbic networks was the fingerprint of PD-MCI patients. This FC-trait might be explored in future studies as a biomarker for PD-MCI.

References: 1. Wolters, A. F. et al. Resting-state fMRI in Parkinson’s disease patients with cognitive impairment: A meta-analysis. Parkinsonism & Related Disorders 0, (2018). 2. Zalesky, A., Fornito, A. & Bullmore, E. T. Network-based statistic: identifying differences in brain networks. Neuroimage 53, 1197–1207 (2010). 3. Amico, E. et al. Mapping the functional connectome traits of levels of consciousness. Neuroimage 148, 201–211 (2017).

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MDS Abstracts - https://www.mdsabstracts.org/abstract/functional-connectome-in-parkinsons-disease-mild-cognitive-impairment/