Objective: To examine the relationship between beta oscillations in the cortico-basal ganglia circuit and daytime vigilance in parkinsonism.

Background: Exaggerated beta oscillations in the cortico-basal ganglia circuit are a pathophysiological signature of Parkinson’s disease (PD) motor signs. Excessive daytime sleepiness is a common non-motor symptom of PD, however, its association with beta oscillations in the cortico-basal ganglia circuit remains unclear. We hypothesized that excessive beta oscillations during wake could be detrimental to the sustenance of wakefulness and suppression of beta oscillations would facilitate wakefulness, therefore, reducing episodes of sleep during daytime.

Method: Simultaneous neural recordings from the subthalamic nucleus (STN) and primary motor cortex (MC) were performed in two parkinsonian nonhuman primates in three conditions: OFF-medication, ON-medication, and during the decay of medication effect. In each condition (n=8 sessions/condition), the vigilance state, i.e., quantity (% of recording time) of wake, drowsy, or sleep, was determined using MC low-frequency (2-5 Hz) power, and the correlation between wake quantity and cortico-basal ganglia beta power during wake periods was assessed.

Results: STN low-beta (7-20 Hz) power negatively correlated with wake quantity in both subjects, suggesting that excessive STN low-beta oscillations are detrimental to the sustenance of wakefulness. The correlation between cortical low-beta power and wake quantity was inconsistent across subjects. Interestingly, the power of subthalamic and cortical high-beta (20-35 Hz) oscillations positively correlated with wake quantity in both subjects.

Conclusion: Our data provides evidence for a relationship between beta oscillations and daytime vigilance in parkinsonism in addition to its known association with PD motor signs. These findings could inform the development of targeted neuromodulation approaches for selective suppression (e.g., low-beta) and/or amplification (e.g., high-beta) of beta oscillations in the cortico-basal ganglia circuit to promote wakefulness in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/relationship-between-cortico-basal-ganglia-beta-oscillations-and-excessive-daytime-sleepiness-in-parkinsonism/