Effects of subthalamic nucleus stimulation on characteristics of EMG activity underlying reaction time in Parkinson's disease

Authors

  • Hatice Kumru MD,

    1. Servei de Neurologia, Hospital Clínic, Departament de Medicina, Facultad de Medicina, Universitat de Barcelona, Institut d'Investigació Biomèdica August Pi i Sunyer (IDIBAPS)
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  • Christopher Summerfield PhD,

    1. Servei de Neurologia, Hospital Clínic, Departament de Medicina, Facultad de Medicina, Universitat de Barcelona, Institut d'Investigació Biomèdica August Pi i Sunyer (IDIBAPS)
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  • Francesc Valldeoriola MD,

    1. Servei de Neurologia, Hospital Clínic, Departament de Medicina, Facultad de Medicina, Universitat de Barcelona, Institut d'Investigació Biomèdica August Pi i Sunyer (IDIBAPS)
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  • Josep Valls-Solé MD

    Corresponding author
    1. Servei de Neurologia, Hospital Clínic, Departament de Medicina, Facultad de Medicina, Universitat de Barcelona, Institut d'Investigació Biomèdica August Pi i Sunyer (IDIBAPS)
    • Unitat d'EMG, Servei de Neurologia, Hospital Clinic, Villarroel, 170, Barcelona, Spain 08036
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Abstract

We examined the effects of high-frequency deep brain stimulation of the subthalamic nucleus (STN-DBS) on characteristics of electromyographic (EMG) activity of the agonist muscle in 8 patients with Parkinson's disease (PD). Patients were examined during STN-DBS (ON), and 30 minutes after switching off both stimulators (OFF). They were asked to make a ballistic movement in paradigms of simple reaction time (SRT) and choice reaction time (CRT) tasks. Onset of movement (MOVonset) was measured as the latency of the initial displacement from baseline of the signal from an accelerometer attached to the dorsum of the hand. In the associated EMG activity, recorded from wrist extensor muscles, we measured onset latency (EMGonset), size of the first EMG burst (EMGsize), and number of EMG bursts (EMGbursts) counted between EMGonset and task execution. MOVonset and EMGonset were significantly shorter in ON than in OFF conditions in CRT. EMGsize was larger, EMGbursts were reduced, and peak of the acceleration profile was larger in ON compared with OFF conditions in both SRT and CRT. Our results indicate that STN-DBS induces a significant improvement in motor performance of reaction time tasks in PD patients. Such improvement is associated with a change in features of the EMG activity suggesting an increase in the excitability of the motor pathways engaged in ballistic movements. © 2003 Movement Disorder Society

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