Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

Frequency analysis may have some advantages over back-averaging in the neurophysiological assessment of patients with suspected cortical myoclonus in whom myoclonic EMG bursts repeat rhythmically at high frequency. However, the clinical utility of EEG-EMG coherence and related EMG-EMG coherence is not established. Equally, there is an incomplete understanding of the physiology of the systems contributing to the coherence evident between signals in cortical myoclonus. Here we address these issues in an investigation of EEG-EMG and EMG-EMG coupling in proximal and distal muscles of the upper extremities in nine patients with multifocal high frequency rhythmic myoclonus due to non-progressive conditions. We found exaggerated coherence between EEG and contralateral EMG and between pairs of ipsilateral EMG signals. The results of frequency analysis of EMG-EMG mirrored those for EEG-EMG, but the former technique was superior in distinguishing a pathologically exaggerated common drive in distal upper limb muscles. Both techniques were more sensitive than back-averaging. Frequency analysis also revealed important disparities between proximal and distal upper limb muscles. In the latter case, the functional coupling between cortex and muscle was dominated by efferent processes. In contrast, there was considerable inter-individual variation in the extent to which EEG-EMG and EMG-EMG coupling in proximal muscles reflected afferent and efferent loops. Thus, the processes sustaining myoclonic discharges may differ for proximal and distal muscles and between patients.


Journal article



Publication Date





326 - 342


Adult, Aged, Aged, 80 and over, Electroencephalography, Electromyography, Female, Hand, Humans, Male, Middle Aged, Motor Cortex, Muscle, Skeletal, Myoclonus, Signal Processing, Computer-Assisted