The phase average wavelength of alpha rhythm in EEG signals of patients with Parkinson’s disease combined with cognitive impairment

OBJECTIVE: To investigate the changes of phase average wavelength of alpha rhythm in different brain regions of patients with Parkinson's Disease (PD) during awake period with eyes closed. METHODS: This study included 54 patients with PD and 30 normal controls. The PD patients were divided into a PD-cognitive normal group (PD-NC) and a PD-cognitive impairment group (PD-CI) based on Mini-Mental State Examination (MMSE) scores. The electroencephalography signals were decomposed at different scales using the Gauss continuous wavelet transform method. The phase average wavelength of the ninth scale (corresponding to the alpha rhythm) was extracted using the conditional sampling and phase averaging method. The alpha-band wavelengths of the background rhythm of different leads were compared between groups. Additionally, the correlation between the wavelength of the ninth scale and MMSE and Montreal Cognitive Assessment (MoCA) scores in PD patients was analyzed. RESULTS: There were significant differences in phase average wavelength at scale nine in each lead among the three groups (P < 0.05). The phase average wavelength of the alpha rhythm in all brain regions corresponding to the ninth scale in PD patients was prolonged compared with the normal controls (P < 0.05). There was a tendency for the PD-CI group to be longer than the PD-NC group, especially in the frontal area, central area and anterior temporal area. The average wavelength of alpha rhythm phase was negatively correlated with MoCA score in PD patients in all leads (P < 0.05), except the right central region (C4) and middle temporal region (T4). CONCLUSIONS: The phase average wavelength of the alpha rhythm in PD patients was longer than that in normal controls, indicating that the alpha rhythm of PD patients was slowed down. With the deterioration of cognitive function, the alpha rhythm of PD patients gradually slowed down. SIGNIFICANCE: The phase average wavelength of the electroencephalography alpha rhythm may become a new parameter for the evaluation of cognitive impairment.