Objective: To characterize changes in synchronized oscillatory activity and coherence between the globus pallidus (GPi) and primary motor cortex (M1) of Parkinson’s disease (PD) patients at rest and during movement.

Background: DBS lead implant surgery offers a unique opportunity to record neuronal activity from subcortical and cortical regions that comprise the basal ganglia thalamo-cortical circuitry. While there are multiple studies examining the changes in local field potential activity from the subthalamic nucleus in patients at rest there are few studies that have characterized the changes in oscillatory activity and coherence within the pallidocortical network during movement.

Method: During microelectrode mapping we recorded neuronal and LFP activity from 3 microelectrodes in the GPi simultaneously with LFP’s from a 2×16 electrocorticography (ECoG) strip centered over M1. These data were collected in 5 patients undergoing implantation of DBS leads both at rest and during a reach-to-target task. MER locations within the GPi were determined using pre-operative high resolution 7T MR images registered to post-operative CT scans.

Results: Synchronized oscillations in the low (13-20Hz) and high (20-35Hz) beta range were suppressed while high frequencies (HFO; 150-400Hz) increased prior to (preparation) and during movement (execution). Movement time (quantified measure of bradykinesia) was correlated to the ratio of low beta:HFO amplitude of modulation (R²=0.93). GPi-cortical coherence in the low-beta range was seen in all patients at rest and was suppressed during movement. Oscillatory activity and GPi-cortical coherence present during rest and modulated with movement were most pronounced in recording sites in posterolateral (sensorimotor) regions of the GPi.

Conclusion: These data indicate that other frequency bands outside of beta (i.e., HFO) are associated with bradykinesia. Thus, a more accurate neural correlate of bradykinesia likely includes interaction between multiple frequency bands. Further, low-beta GPi-cortical coherence provides another potential biomarker of PD and may be explored for use in closed-loop stimulation paradigms. Identifying subregions of GPi expressing these neural correlates may be used to guide patient-specific DBS lead placement and directional stimulation in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/movement-related-modulation-of-beta-high-frequency-oscillations-and-low-beta-pallido-cortical-coherence-in-parkinsons-disease/