Decoding Finely Tuned Gamma Oscillations in Chronic Deep Brain Stimulation for Parkinson's Disease

Area of Science:

• Neuroscience
• Biomedical Engineering

Background:

• Finely tuned Gamma (FTG) activity, including spontaneous (sFTG) and entrained (eFTG) oscillations, is associated with Parkinson's disease (PD) on-medication states and dyskinesia.
• FTG is a potential physiomarker for adaptive deep brain stimulation (aDBS), but its precise characteristics and determinants are not fully understood.

Purpose of the Study:

• To explore the prevalence of FTG in PD patients.
• To investigate the clinical correlates of FTG.
• To examine associations between FTG and deep brain stimulation (DBS) parameters to inform future research.

Main Methods:

• Retrospective analysis of local field potentials (LFPs) from the subthalamic nucleus (STN) in PD patients using Percept neurostimulators.
• Data analysis focused on predefined clinically relevant questions regarding FTG activity.

Main Results:

• Spontaneous FTG (sFTG) occurred in 19% of STNs, and 1:2 eFTG in 28%.
• FTG was consistently linked to medication, stimulation, or stun-effect induced ON-states, but not always to dyskinesia.
• sFTG often occurred during transitions to eFTG, and beta activity frequently co-occurred with FTG, showing an inverse relationship with 1:2 eFTG. 1:2 eFTG occurrence depended on stimulation amplitude.

Conclusions:

• FTG appears to be an indicator of the overall ON-state in PD, irrespective of dyskinesia.
• The 1:2 eFTG pattern likely represents neural population entrainment and can occur independently of sFTG, influenced by stimulation amplitude.
• Further research is needed to clarify interactions between beta activity and FTG subtypes, accounting for artifacts, to enhance aDBS algorithms.