Dynamic channelwise functional-connectivity states extracted from resting-state EEG signals of patients with Parkinson's disease

Background Parkinson's disease (PD) is a progressive neurodegenerative disease that usually happens to elderly people, with a wide range of motor and dementia symptoms. An objective and convenient biomarker for PD detection is extremely valuable, especially one that could be acquired non-invasively and low-costly. To this end, this study used resting-state scalp electroencephalography (EEG) signals to explore dynamic functional-connectivity (dFC) states between each pair of EEG recording channels, without source localization. Methods dFC refers to synchronization patterns over time between each pair of EEG channels. First, five frequency bands were extracted from EEG signals with fourth-order Butterworth bandpass filter, including delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), beta (8-30 Hz) and gamma (30-50 Hz). Then, after non-random joint fluctuation was measured with weighted symbolic mutual information (wSMI) algorithm, whole-brain dynamic channelwise dFC states were estimated, and classified with k-means clustering. At last, FC state occurrences were calculated, and ANOVA analyses were performed for each state. Two open-source resting-state EEG data sets (https://doi.org/10.18112/openneuro.ds002778.v1.0.4: 32 channels, 16 health controls and 15 PD subjects. https://doi.org/10.18112/openneuro.ds003490.v1.1.0: 64 channels, 25 health controls and 25 PD subjects) were used to test our methods. Results Significant changes in proportions of various dFC states within beta frequency-band were consistently observed in these both data sets (p value < 0.05). Conclusions Our findings suggest that channelwise dFC states within beta frequency-band directly extracted from resting-state scalp-EEG recordings could potentially serve as a biomarker of PD.