Objective:

To examine differences in medication-state modulation of motor-cortical low-beta power and cerebellum-related connectivity between tremor-dominant (TD) and postural instability/gait difficulty (PIGD) subtypes of Parkinson's disease (PD).

Approach:

• Participants: Enrolled 12 healthy controls, 20 patients with PIGD, and 18 with TD.
• EEG Analysis: Conducted 64-channel eyes-closed resting-state EEG in a fixed OFF-to-ON sequence.
• Statistical Methods: Used linear mixed-effects models for primary effects and controlled exploratory analyses with Benjamini–Hochberg false discovery rate (BH-FDR).

Key Findings:

• Low-beta relative power spectral density (PSD) in the primary motor cortex (M1) showed a significant group × state interaction (χ2(1) = 5.84, p = 0.016; β = −1.45 dB, 95% CI [−2.59, −0.32]).
• Low-beta power increased in the PIGD group from OFF to ON (+1.26 dB, 95% CI [0.48, 2.04]) but showed little change in the TD group (−0.20 dB, 95% CI [−1.02, 0.63]).
• Exploratory analyses revealed differences in high-beta ΔwPLI between cerebellar regions, surviving BH-FDR correction (q = 0.028).

Interpretation:

Distinct medication-state modulation of motor-cortical low-beta power was identified between PD subtypes, with M1 low-beta PSD being the most consistent electrophysiological difference.

Limitations:

• Findings on cerebellum-related connectivity were limited to exploratory effects and require independent replication.
• The small sample size may affect generalizability.

Conclusion:

Tremor-dominant and PIGD subtypes exhibit different responses in motor-cortical low-beta activity to medication, highlighting the need for further research.