Differential distribution of coherence between beta-band subthalamic oscillations and forearm muscles in Parkinson's disease during isometric contraction.

OBJECTIVE: Under rest condition, beta-band (13-30Hz) activity in patients with Parkinson's disease (PD) is prominent in the subthalamic nucleus (STN). However, the beta-band coupling between STN and muscle activity, its distribution and relation to motor symptoms remains unclear.
METHODS: Using up to five electrodes, we recorded local field potentials (LFPs) above (zona incerta, ZI) and within the STN at different recording heights in 20 PD patients during isometric contraction. Simultaneously, we registered activity of the contralateral flexor and extensor muscle. We analysed LFP-EMG coherence to estimate coupling in the frequency domain.
RESULTS: Coherence analysis showed beta-associated coupling in the ZI and STN with more significant LFP-EMG coherences in the STN. Coherence varied depending on the localisation of the LFP and muscles. We found significant difference between coherence of the extensor and the flexor muscle to the same LFP (p=0.045).
CONCLUSIONS: We demonstrated that coherence between beta-band oscillations and forearm muscles are differentially distributed in the subthalamic region and between the forearm muscles in Parkinson's disease during isometric contraction. However, the significant LFP-EMG coupling did not associate with motor deficits in PD patients. SIGNIFICANCE: The differential distribution of beta-band activity in the STN highlights the importance of a topographically distinct therapeutic modulation.