Analysis of high-frequency electroencephalographic-electromyographic coherence elicited by speech and oral nonspeech tasks in Parkinson's disease

Purpose: Corticomuscular electroencephalographic-electromyographic (EEG-EMG) coherence elicited by speech and nonspeech oromotor tasks in healthy participants and those with Parkinson's disease (PD) was examined. Hypotheses were the following: (a) corticomuscular coherence is demonstrable between orbicularis oris (OO) muscles' EMG and scalp EEG recording; (b) the presence, location, and magnitude of coherence is task specific; (c) differences in corticomuscular coherence patterns exist between healthy and PD participants; and (d) differences will manifest as either increased or decreased coherence values in certain frequency bands, with EEG localization at primary sensorimotor cortex and/or supplementary motor area (SMA). Method: Simultaneous EEG, EMG (OO), and speech samples were recorded on 20 healthy and 20 PD participants during speech and nonspeech tasks. Fast Fourier transform and coherence analysis was performed with Neuroscan software on 1,000 randomly generated epochs per task per group. Corticomuscular coherence was analyzed between each EEG electrode and right and left superior and inferior OO muscles up to 200 Hz. Significant coherence peaks exceeded 95% confidence limits (.003). Results: Corticomuscular coherence existed for both groups and for all tasks, but to varying degrees in primary sensorimotor cortex and SMA. Conclusions: Results support task specificity for both groups and, in PD, a diminished modulation flexibility linked to the sensorimotor area and reduced corticomuscular coherence at the SMA.