Research article summary (published 30 Aug 2003):

EMG contamination of EEG: spectral and topographical characteristics.

Full Abstract

OBJECTIVE: Electromyogram (EMG) contamination is often a problem in electroencephalogram (EEG) recording, particularly, for those applications such as EEG-based brain-computer interfaces that rely on automated measurements of EEG features. As an essential prelude to developing methods for recognizing and eliminating EMG contamination of EEG, this study defines the spectral and topographical characteristics of frontalis and temporalis muscle EMG over the entire scalp. It describes both average data and the range of individual differences. METHODS: In 25 healthy adults, signals from 64 scalp and 4 facial locations were recorded during relaxation and during defined (15, 30, or 70% of maximum) contractions of frontalis or temporalis muscles. RESULTS: In the average data, EMG had a broad frequency distribution from 0 to >200 Hz. Amplitude was greatest at 20-30 Hz frontally and 40-80 Hz temporally. Temporalis spectra also showed a smaller peak around 20 Hz. These spectral components attenuated and broadened centrally. Even with weak (15%) contraction, EMG was detectable (P<0.001) near the vertex at frequencies >12 Hz in the average data and >8 Hz in some individuals. CONCLUSIONS: Frontalis or temporalis muscle EMG recorded from the scalp has spectral and topographical features that vary substantially across individuals. EMG spectra often have peaks in the beta frequency range that resemble EEG beta peaks. SIGNIFICANCE: While EMG contamination is greatest at the periphery of the scalp near the active muscles, even weak contractions can produce EMG that obscures or mimics EEG alpha, mu, or beta rhythms over the entire scalp. Recognition and elimination of this contamination is likely to require recording from an appropriate set of peripheral scalp locations.

Author information

Author/s: Goncharova, I I (II); McFarland, D J (DJ); Vaughan, T M (TM); Wolpaw, J R (JR);

Affiliation: Laboratory of Nervous System Disorders, Wadsworth Center, New York State Department of Health and State University of New York, Empire State Plaza, P.O. Box 509, Albany, NY 12201-0509, USA. gonchar(-atsign-)wadsworth.org

Grants: EB00856 (Agency:NIBIB NIH HHS) ; HD30146 (Agency:NICHD NIH HHS)

Journal and publication information

Publication Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.

Journal: Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology (Clin Neurophysiol), published in Netherlands. (Language: eng)

Reference: 2003-Sep; vol 114 (issue 9) : pp 1580-93

Dates: Created 2003/09/01; Completed 2003/11/04; Revised 2008/09/10;

PMID: 12948787, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adolescent Adult Automatic Data Processing Brain - physiology Brain Mapping Electrodes, Implanted Electroencephalography Electromyography

Female Humans Individuality Male Middle Aged Muscle Contraction - physiology Muscles - physiology Relaxation - physiology

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