Increased Activation of Default Mode Network in Early Parkinson’s With Excessive Daytime Sleepiness

BACKGROUND AND OBJECTIVES: The underlying neuropathology of excessive daytime sleepiness (EDS) remains elusive in Parkinson’s disease (PD). We aim to investigate neural network changes that underlie EDS in PD. METHODS: Early PD patients comprising eighty-one patients without EDS (EDS−) and seventeen patients with EDS (EDS+) received a resting state functional MRI scan and the Epworth Sleepiness Scale (ESS). Connectivities within the default mode network (DMN), motor and basal ganglia networks were compared between the EDS+ and EDS− groups. Correlations between network connectivity and the severity of EDS were investigated through linear regression. RESULTS: EDS+ patients displayed a trend of increased network connectivity of the posterior DMN (pDMN). A significant positive correlation was found between connectivity of the ventromedial prefrontal cortex in the pDMN and ESS. CONCLUSION: EDS+ patients are likely to display increased activation in the DMN, suggesting neural compensation in early PD or impaired attentiveness due to mechanisms such as mind-wandering.