Abnormal Complexity Related to Frequency in Prodromal Parkinson’s disease and Parkinson’s disease

Patients with Parkinson’s disease (PD) mainly manifested dyskinesia and lack of information processing ability. Resting-state fMRI (rs-fMRI) brain signal has been used to study brain activity. However, few studies apply complexity analysis to functional brain imaging. It is still not clear whether Prodromal Parkinson’s disease (PPD) patients and PD patients have abnormal complexity, and whether abnormal complexity is related to the frequency band. So we explored the signal complexity of 21 normal controls (NCs), 26 PPD patients, and 47 PD patients in four frequency bands based on fuzzy entropy (FE). In slow 3 and slow 2 frequency bands, the complexity of patients with PD is higher than that of the PPD patients and NCs. The complexity of the NCs was higher than that of PPD patients. Significant complexity anomalies were found in the caudate, superior frontal gyrus, thalamus, precuneus, and precentral gyrus. There are significant correlations between complexity and regional homogeneity (ReHo), the fractional amplitude of low-frequency fluctuation (fALFF), gray matter density/volume (GMD/V), and clinical scores. Results showed that patients had abnormal complexity, and abnormal complexity is related to the frequency band. The complexity analysis of brain signals in different frequency bands can be used to explore the underlying mechanism of neurological diseases.