EEG Sub-band Abnormality of Early-stage Parkinson's Disease with Mild Cognitive Impairment

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Early-stage Parkinson's disease (PD) patients with mild cognitive impairment (MCI) are at a high risk of dementia, and identifying the abnormal brain activity associated with MCI is critical for the early diagnosis of PD. In this study, we analyzed the EEG features of different sub-bands associated with the MCI in the early-stage PD patients. We recorded electroencephalogram (EEG) signals from 39 subjects during the resting state, including 17 early-state PD patients with MCI and 22 healthy control (HC) subjects. Welch’s method was used to compute the power spectrum density at each EEG sub-band. It was shown that the alpha rhythm in PD patients was characterized by a higher relative power, while the beta and gamma rhythms exhibited lower relative powers as compared to the HC group. We applied the phase lag index (PLI) to quantify the phase synchronization of pair-wise channels at different sub-bands and then reconstructed the cross-band functional networks. We found that there were significantly different synchronization degrees in theta, alpha and beta bands between two groups. The phase synchronization between different regions of the whole brain in theta-alpha, alpha-delta, and beta-theta cross-band also showed significant abnormalities as compared to the HC group. The findings indicated that the abnormalities in EEG alpha, beta, and gamma activities occurred at the early stages of PD with MCI, and the power spectra and cross-band connectivity analysis may be a promising method to detect such abnormalities.