Objective: To investigate the dynamics of beta bursts in subthalamic nucleus (STN) local field potentials (LFP) in patients with Parkinson’s disease (PD) before and after administration of levodopa. 

Background: Elevated basal ganglia beta activity can be suppressed by dopaminergic medication in patients with PD and the degree of suppression is correlated with the relative improvement in motor symptoms. Basal ganglia beta activity is not constantly elevated but fluctuates and appears in beta bursts, which have a state dependent dynamic, as recently shown for the resting and movement state in non-human primates. Here we investigate how levodopa interferes with beta bursts in comparison to the OFF levodopa state. 

Methods: Local field potentials were recorded in the STN of PD patients during temporary lead externalisation. The recordings took place at rest following overnight withdrawal of levodopa and after administration of levodopa. Beta bursts were defined by applying an amplitude threshold and burst properties were compared between the two conditions. 

Results: Our results show that beta bursts come in different durations and amplitudes. Burst duration and amplitude have a strong positive relationship during both OFF and ON levodopa state, in line with a progressive increase in beta synchronisation over time. Strikingly, there was a reduction of long duration high amplitude bursts and an increase in short duration low amplitude beta bursts after levodopa administration. The overall burst duration and amplitude were therefore decreased ON levodopa. Beta bursts also overlapped in time in the left and right STN more than expected by chance, and such overlap was reduced ON levodopa. Importantly, short duration beta bursts were negatively correlated with motor impairment, while the opposite was true for long beta bursts. Findings were preserved across different percentile amplitude thresholds.

Conclusions: We demonstrate that dopaminergic activity regulates pathological beta synchronisation by reducing long duration – high amplitude beta bursts and thereby limiting the uncontrolled beta synchronisation related to motoric impairment in PD. The tendency for beta bursts to synchronise between hemispheres is also dopamine dependent. These results highlight the importance of the temporal dynamics and properties of beta bursts in PD and have important implications for the optimal design of closed loop DBS algorithms.    

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MDS Abstracts - https://www.mdsabstracts.org/abstract/dynamics-of-subthalamic-nucleus-beta-bursts-in-parkinsons-disease-during-on-and-off-dopaminergic-state/