Functional brain networks and cognitive deficits in Parkinson's disease

Abstract

Abstract: Graph-theoretical analyses of functional networks obtained with resting-state functional mag-netic resonance imaging (fMRI) have recently proven to be a useful approach for the study of the sub-strates underlying cognitive deficits in different diseases. We used this technique to investigate whethercognitive deficits in Parkinson's disease (PD) are associated with changes in global and local networkmeasures. Thirty-six healthy controls (HC) and 66 PD patients matched for age, sex, and education wereclassified as having mild cognitive impairment (MCI) or not based on performance in the three mainlyaffected cognitive domains in PD: attention/executive, visuospatial/visuoperceptual (VS/VP), anddeclarative memory. Resting-state fMRI and graph theory analyses were used to evaluate network meas-ures. We have found that patients with MCI had connectivity reductions predominantly affecting long-range connections as well as increased local interconnectedness manifested as higher measures of cluster-ing, small-worldness, and modularity. The latter measures also tended to correlate negatively with cogni-tive performance in VS/VP and memory functions. Hub structure was also reorganized: normal hubsdisplayed reduced centrality and degree in MCI PD patients. Our study indicates that the topologicalproperties of brain networks are changed in PD patients with cognitive deficits. Our findings providenovel data regarding the functional substrate of cognitive impairment in PD, which may prove to havevalue as a prognostic marker.