Objective: To examine the neural activity during turning in Parkinson’s disease (PD).

Background: Turning is impaired in PD with links to freezing of gait (FOG) and falls risk. Specifically, turning is slow and elicits FOG episodes in PD, which can worsened by performing a secondary task when turning (dual-tasking). The neural mechanisms underlying turning deficit in PD are unclear, which makes intervention difficult. Examination of the neural activity involved during turning in PD may allow greater understanding of the mechanisms involved in turning deficit, which could help develop effective therapeutics. Mobile electroencephalogram (EEG) is a neuroimaging technique that can be useful in investigating neural activity during turning.

Method: 40 people with PD (n=20 with FOG and n=20 without FOG) turned-in-place 360 degrees under single and dual-task (forward digit span) conditions for two minutes, while a 32-channel mobile EEG system (Mobita, TMSi, Netherlands) recorded neural activity and synchronized inertial sensors measured turning. EEGLAB software was used to process EEG signals to derive neural activity, specifically source localized independent component (IC) clusters and their power spectral densities; Delta (δ:1‐4Hz), Theta (q:4‐8Hz), Alpha (α:8‐13Hz), Beta (b:13‐30Hz) and Gamma (γ:30‐50Hz) band. We identified 249 ICs in total and formed 6 clusters with source locations in the frontal, parietal and occipital cortices.

Results: Turning velocity (p<.001) and duration (p=.002) were impaired in PD with FOG compared to without FOG, particularly when performing a dual-task (p<.001). EEG analysis showed no significant group difference in neural activity. However, within PD groups neural activity was altered in specific regions when turning under dual-task compared to single-task conditions. Specifically, PD with FOG had reduced b-band and increased γ-band frontal cortex activity (p<0.05), whereas PD without FOG had reduced b-band and increased γ-band parietal cortex activity (p<0.05). This may indicate reduced cognitive (attentional) processing and increased sensorimotor processing in the frontal cortex for people with PD and FOG, and in the parietal cortex for people with PD without FOG.

Conclusion: Initial results demonstrate that turning may influence neural activity in specific regions in PD, with different regional activity in those with FOG when performing a dual-task. Differences may underpin turning impairment in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/neural-activity-during-turning-in-parkinsons-influence-of-dual-task-and-freezing/