Objective: To begin exploring if and how bi-hemispheric cortical phase synchronization (PS), as reflected by electroencephalography (EEG), during free overground walking, is associated with gait disturbances in Parkinson’s disease (PD), in comparison to healthy elderly subjects.

Background: Gait and postural disturbances significantly affect the quality of life of PD patients. The pathophysiology underlying walking impairments in PD is not fully understood.

Methods: We examined 11 idiopathic PD patients (68±8 y) and 7 elderly subjects (64±9 y) performing 1)two minutes quiet standing 2)back/forth straight line corridor walking (turns and freezing episodes, if occurred, omitted from analysis) 3)alternating 4)simultaneous hand tapping. EEG was recorded with a 32 electrode array (sampling rate 2048 Hz). The Fourier-mode PS method was used to quantify synchronization in periodic cortical activation between the two hemispheres (PS ranges: 0 to 1, representing no to maximal synchronization). The theta (3.9-7.8 Hz), alpha (7.8-15.6 Hz) and beta (15.6-31.2 Hz) bands were studied. Non-parametric statistics was used.

Results: Bi-hemispheric PS was significantly stronger among PD patients versus controls while standing: Mean PS(±SEM) (grand averaged across the three bands) 0.55±0.04 and 0.45±0.01, respectively (p <0.001). This difference was even larger while walking: 0.61±0.04 for PD and 0.43±0.01 for controls, (p <0.001). Mean PS ratios for gait to stance were 1.13 ±0.07 for PD and 0.96±0.02 for controls, (p=0.056). Hand tapping also led to increased PS, but differed less between groups (p=0.098). Higher PS values were seen in the simultaneous tapping (0.64 ±0.04) vs. alternating tapping (0.58±0.03) only for the PD group (p=0.062). The mean PS ratios for simultaneous to alternating tapping were 1.10±0.04 for PD and 1.03±0.03 for controls (p=0.35).

Conclusions: Our findings suggest that excessive bi-hemispheric cortical synchronization may contribute, or alternatively be consequential to stance and gait disturbances in PD. This study is one of handful addresing cortical activity while walking in PD patients and the only one looking at bi-hemispheric synchronization, contrasting walking with other bilateral movements. We find it important to draw the community’s attention to the potential relationship between impairments in cortical networks interactions and PD related motor impairments.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/bi-hemispheric-phase-synchronization-in-patients-with-parkinsons-disease-during-stance-gait-and-upper-limb-motor-tasks/