Parkinson subtype-specific Granger-causal coupling and coherence frequency in the subthalamic area

Area of Science:

• Neuroscience
• Biomedical Engineering
• Movement Disorders

Background:

• Parkinson's disease (PD) involves abnormal connectivity between muscle activity and the subthalamic nucleus (STN).
• Specific frequency components driving afferent information flow in PD remain unclear.
• Different PD subtypes may exhibit unique connectivity patterns.

Purpose of the Study:

• To investigate frequency-specific coherence and causality between STN local field potentials (LFPs) and arm muscle electromyograms (EMGs).
• To compare these connectivity patterns in akinetic-rigid (AR) and tremor-dominant (TD) Parkinson's disease patients.

Main Methods:

• Recorded STN LFPs and surface EMGs from contralateral arm muscles during forearm lifts in 18 AR and 8 TD PD patients.
• Analyzed coherence and causality across different frequency bands during intraoperative recordings.
• Differentiated between afferent (muscle-to-STN) and efferent (STN-to-muscle) connections.

Main Results:

• TD patients showed significantly more afferent connections than AR patients, especially during tremor periods.
• Within the STN, afferent connections were linked to 4-8Hz and 8-12Hz coherence; during tremor, 12-20Hz coherence showed more afferent than efferent connections.
• AR patients displayed more afferent than efferent connections dorsally to the STN in the 12-16Hz range.

Conclusions:

• Findings support distinct pathological oscillations and pathways in AR and TD Parkinson's disease subtypes.
• Highlights the importance of frequency-specific connectivity analysis for understanding PD heterogeneity.
• Suggests potential for subtype-specific therapeutic targets based on connectivity differences.