Surface Laplacian of scalp electrical signals and independent component analysis resolve EMG contamination of electroencephalogram

Sean Fitzgibbon, Dylan DeLosAngeles, Trent Lewis, David Powers, Emma Whitham, John Willoughby, Kenneth Pope

    Research output: Contribution to journalArticle

    22 Citations (Scopus)

    Abstract

    The serious impact of electromyogram (EMG) contamination of electroencephalogram (EEG) is well recognised. The objective of this research is to demonstrate that combining independent component analysis with the surface Laplacian can eliminate EMG contamination of the EEG, and to validate that this processing does not degrade expected neurogenic signals. The method involves sequential application of ICA, using a manual procedure to identify and discard EMG components, followed by the surface Laplacian. The extent of decontamination is quantified by comparing processed EEG with EMG-free data that was recorded during pharmacologically induced neuromuscular paralysis. The combination of the ICA procedure and the surface Laplacian, with a flexible spherical spline, results in a strong suppression of EMG contamination at all scalp sites and frequencies. Furthermore, the ICA and surface Laplacian procedure does not impair the detection of well-known, cerebral responses; alpha activity with eyes-closed; ERP components (N1, P2) in response to an auditory oddball task; and steady state responses to photic and auditory stimulation. Finally, more flexible spherical splines increase the suppression of EMG by the surface Laplacian. We postulate this is due to ICA enabling the removal of local muscle sources of EMG contamination and the Laplacian transform being insensitive to distant (postural) muscle EMG contamination.

    Original languageEnglish
    Pages (from-to)277-284
    Number of pages8
    JournalInternational Journal of Psychophysiology
    Volume97
    Issue number3
    Early online date2015
    DOIs
    Publication statusPublished - 1 Sep 2015

    Keywords

    • EEG
    • Electromyogram
    • Evoked response
    • Independent component analysis
    • Oddball task
    • Steady state response
    • Surface Laplacian

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