EEG monitoring is feasible and reliable during simultaneous transcutaneous electrical spinal cord stimulation

McGeady, C., Vučković, A. , Zheng, Y.-P. and Alam, M. (2021) EEG monitoring is feasible and reliable during simultaneous transcutaneous electrical spinal cord stimulation. Sensors, 21(19), 6593. (doi: 10.3390/s21196593)

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Transcutaneous electrical spinal cord stimulation (tSCS) is a non-invasive neuromodulatory technique that has in recent years been linked to improved volitional limb control in spinal-cord injured individuals. Although the technique is growing in popularity there is still uncertainty regarding the neural mechanisms underpinning sensory and motor recovery. Brain monitoring techniques such as electroencephalography (EEG) may provide further insights to the changes in coritcospinal excitability that have already been demonstrated using other techniques. It is unknown, however, whether intelligible EEG can be extracted while tSCS is being applied, owing to substantial high-amplitude artifacts associated with stimulation-based therapies. Here, for the first time, we characterise the artifacts that manifest in EEG when recorded simultaneously with tSCS. We recorded multi-channel EEG from 21 healthy volunteers as they took part in a resting state and movement task across two sessions: One with tSCS delivered to the cervical region of the neck, and one without tSCS. An offline analysis in the time and frequency domain showed that tSCS manifested as narrow, high-amplitude peaks with a spectral density contained at the stimulation frequency. We quantified the altered signals with descriptive statistics—kurtosis, root-mean-square, complexity, and zero crossings—and applied artifact-suppression techniques—superposition of moving averages, adaptive, median, and notch filtering—to explore whether the effects of tSCS could be suppressed. We found that the superposition of moving averages filter was the most successful technique at returning contaminated EEG to levels statistically similar to that of normal EEG. In the frequency domain, however, notch filtering was more effective at reducing the spectral power contribution of stimulation from frontal and central electrodes. An adaptive filter was more appropriate for channels closer to the stimulation site. Lastly, we found that tSCS posed no detriment the binary classification of upper-limb movements from sensorimotor rhythms, and that adaptive filtering resulted in poorer classification performance. Overall, we showed that, depending on the analysis, EEG monitoring during transcutaneous electrical spinal cord stimulation is feasible. This study supports future investigations using EEG to study the activity of the sensorimotor cortex during tSCS, and potentially paves the way to brain–computer interfaces operating in the presence of spinal stimulation.

Item Type:Articles
Keywords:Transcutaneous spinal cord stimulation, electroencephalography, artifact removal, brain–computer interface, BCI, rehabilitation.
Glasgow Author(s) Enlighten ID:McGeady, Ciaran and Vuckovic, Dr Aleksandra
Creator Roles:
McGeady, C.Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Data curation, Writing – original draft, Visualization
Vučković, A.Conceptualization, Validation, Writing – review and editing
Authors: McGeady, C., Vučković, A., Zheng, Y.-P., and Alam, M.
College/School:College of Science and Engineering > School of Engineering > Biomedical Engineering
Journal Name:Sensors
ISSN (Online):1424-8220
Published Online:02 October 2021
Copyright Holders:Copyright © 2021 The Authors
First Published:First published in Sensors 21(19): 6593
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
172865EPSRC DTP 16/17 and 17/18Mary Beth KneafseyEngineering and Physical Sciences Research Council (EPSRC)EP/N509668/1Research and Innovation Services