Cortico-muscular coherence in advanced Parkinson's disease with deep brain stimulation

Objective: Cortico-muscular coherence (CMC) is thought to reflect the interplay between cortex and muscle in motor coordination. In Parkinson's disease (PD) patients, levodopa has been shown to enhance CMC. This study examined whether subthalamic nucleus (STN) deep brain stimulation (DBS) affects the CMC in advanced PD. Methods: Magnetoencephalography (MEG) and electromyography (EMG) measurements were done simultaneously both with DBS on and off to determine the CMC during wrist extension. The spatiotemporal signal space separation (tSSS) was used for artifact suppression. Results: CMC peaks between 13 and 25 Hz were found in 15 out of 19 patients. The effect of DBS on CMC was variable. Moreover, the correlation between CMC and motor performance was inconsistent; stronger CMC did not necessarily indicate better function albeit tremor and rigidity may diminish the CMC. Patients having CMC between 13 and 25 Hz had the best motor scores at the group level. Conclusions: DBS modifies the CMC in advanced PD with large interindividual variability. Significance: DBS does not systematically modify CMC amplitude in advanced PD. The results suggest that some components of the CMC may be related to the therapeutic effects of DBS. (C) 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.