Objective: Parkinson’s disease (PD) is a neurological disorder with no reliable biomarkers. We aimed to investigate naturalistic paradigms as functional biomarkers that distinguish between PD patients and controls as well as track disease progression.

Background: Naturalistic paradigms involve presenting complex, realistic stimuli, such as compelling movie clips, while neural activity is measured. Distinct neural networks are activated and vary in a specific manner over the time-course of the narrative. Synchronicity over time in distinct networks compared to young healthy control data, provides an innovative means for probing active sensory and cognitive processing even in patients differing greatly in cognitive or motor abilities. Fronto-parietal control network (FPCN) is involved in the modulation of attention between internal and external stimuli and is predicted to be the first higher-order network affected in PD.  Many areas of the FPCN are reciprocally connected to the caudal motor area of the striatum, the first striatal area deprived of dopamine. Default mode network is involved in introspective thought and is activated during idle relaxation.  It is expected to be the last network affected in PD as areas are reciprocally connected to the later-degenerating ventral tegmental area.

Method: 16 patients with PD and 15 matched healthy controls were tested twice, once on and the other off dopaminergic medication. Participants watched two film clips, one during each session, while brain activity was simultaneously acquired using fMRI.  Synchronicity was measured by the number of activated voxels within each network that positively correlate with the timecourses from the young dataset.

Results: Synchronicity within FPCN was significantly greater in healthy controls, compared to PD patients when both were tested in the OFF state. Additionally, synchronicity within the DMN network was sensitive to disease progression as it was significantly reduced in patients in the early compared to late-stages of PD, as measured by their daily dose of levodopa.

Conclusion: Synchronicity in the FPCN and DMN networks while viewing short films was sensitive to both distinguish PD patients from controls, as well as track disease progression.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/functional-biomarkers-of-parkinsons-disease-changes-in-brain-wide-network-connectivity-in-default-mode-and-fronto-parietal-control-networks/