Intermuscular coherence in Parkinson's disease: effects of subthalamic nucleus stimulation

It remains unclear how high frequency stimulation of the subthalamic nucleu s (STN) improves parkinsonism. We hypothesized that stimulation may affect the organization of the cortical drive to voluntarily activated muscle. Nor mally this is characterized by oscillations at 15-30 Hz, manifest in cohere nce between muscles in the same frequency band. We therefore investigated t he effects of STN stimulation on electromyographic (EMG) activity in co-con tracting distal arm muscles in nine subjects with Parkinson's disease off d rugs. Without stimulation, coherence between EMG signals was diminished at 15-30 Hz compared with nine controls. STN stimulation increased coherence i n the 15-30 Hz band, so that it approached that in healthy subjects. The re sults suggest that STN stimulation facilitates the normal cortical drive to muscles. NeuroReport 12:1113-1117 (C) 2001 Lippincott Williams & Wilkins.