Decoding Finely-Tuned Gamma Oscillations in Chronic Deep Brain Stimulation for Parkinson’s Disease
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Background
Finely-tuned gamma (FTG) activity, occurring as a narrowband oscillation between 60–100Hz or entrained to half the stimulation frequency, has been observed during ON periods and dyskinesia in Parkinson’s disease (PD). However, the mechanisms and conditions causing FTG remain unclear. This study characterizes FTG in PD patients undergoing subthalamic nucleus (STN) deep brain stimulation (DBS), examining its prevalence and relationship with patient characteristics and stimulation parameters.
Methods
Local field potentials (LFP) recorded across PD patients implanted with Sensight TM leads and a Percept TM PC neurostimulator were retrospectively analyzed for the occurrence of FTG. A comprehensive list of clinically relevant questions was composed to guide the analysis.
Results
Across LFP from 67 PD patients (134 STN) in various clinical states, naturally occurring (naive) and entrained FTG were observed in 11% and 33% of STN, respectively. Entrainment was more frequent during 180Hz than 125/130Hz simulation, but occasionally showed an artifactual origin. In line with the Arnold Tongue framework 1:2 entrainment ceased at high stimulation amplitudes, and showed an inverse relation to 1:1 entrainment. In specific cases, activity at the stimulation frequency was seen in the non-stimulated contralateral hemisphere.
Conclusions
This study provides novel insights into the dynamics and prevalence of both naive and entrained FTG in PD patients with STN-DBS across various clinical states. The study confirms the possibility of 1:1 entrainment but also shows the selective occurrence, potential artifactual origin, and cross-hemisphere influences of entrainment. Future research should investigate the mechanistic pathways underlying FTG, and its value in adaptive DBS.
