Objective: We propose that abnormal EEG power dynamics during sleep are associated not only glymphatic dysfunction but also signal fundamental changes in resting-state functional connectivity (FC) between different large-scale networks.

Background: Dysfunction within thalamocortical circuitry in Parkinson’s disease (PD) generate abnormal patterns of bioelectrical activity that underlie different PD symptoms, including sleep disturbances. Impaired brain function, specifically the inability to regulate sleep stage transitions and maintain the spatiotemporal evolution of EEG power is associated with diminished glymphatic clearance. This deficit, in turn, accelerates the progression of neurodegeneration and dementia development.

Method: Sleep quality and cognitive function were evaluated in 26 PD patients and 25 healthy controls using standardized clinical scales. EEG spectral power analysis was performed in the first and last cycles of night sleep. Rs-fMRI data were analyzed using the SPM12 with the CONN toolbox. The diffusion tensor imaging analysis along the perivascular space index (DTI-ALPS) was calculated to evaluate the glymphatic system.

Results: A defining observation was the lack of significant changes in delta power during NREM stage 3 between the first and last sleep cycles in PD patients. In contrast, healthy controls exhibited a marked physiological decline in slow-wave activity (SWA) and spectral power by the end of the sleep period (p≤0,001). Furthermore, PD patients demonstrated a global reduction in SWA predominantly in the frontal regions with a disruption of the anterior-posterior gradient of brain bioelectrical activity. Reduced SWA was positively correlated with lower MoCA scores and showed a significant association with both poorer Spiegel Sleep Questionnaire outcomes and diminished DTI-ALPS indices. fMRI showed reduced intra-network FC within the  Default Mode the Salience Network nodes. Notably, the cingulate gyrus exhibited significantly weakened connectivity with the prefrontal, orbitofrontal, and middle temporal cortices, as well as the posterior cerebellar lobe (р≤0,002).

Conclusion: Dysregulation SWA topography and dynamics during sleep is reflected in a decrease in the cingulate gyrus – cerebral cortex FC and can probably be considered as one of the mechanisms of impaired glymphatic clearance.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/sleep-slow-wave-activity-topography-and-dynamics-in-pd-relationships-with-resting-state-fmri-data-and-glymphatic-clearance/