Surface Laplacian of Central Scalp Electrical Signals is Insensitive to Muscle Contamination
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Date
2013-01
Authors
Fitzgibbon, Sean Patrick
Lewis, Trent Wilson
Powers, David Martin
Whitham, Emma Mary
Willoughby, John Osborne
Pope, Kennith
Journal Title
Journal ISSN
Volume Title
Publisher
IEEE - Institute of Electrical and Electronics
Rights
© 2012 IEEE - Institute of Electrical and Electronics Engineers.
Rights Holder
IEEE - Institute of Electrical and Electronics Engineers.
Abstract
Abstract—Objective: To investigate the effects of surface
Laplacian processing on gross and persistent electromyographic
(EMG) contamination of electroencephalographic (EEG) signals
in electrical scalp recordings.
Methods: We made scalp recordings during passive and active
tasks, on awake subjects in the absence and in the presence of
complete neuromuscular blockade. Three scalp surface
Laplacian estimators were compared to left ear and common
average reference (CAR). Contamination was quantified by
comparing power after paralysis (brain signal, B) with power
before paralysis (brain plus muscle signal, B+M). Brain:Muscle
(B:M) ratios for the methods were calculated using B and
differences in power after paralysis to represent muscle (M).
Results: There were very small power differences after
paralysis up to 600 Hz using surface Laplacian transforms (B:M>
6 above 30 Hz in central scalp leads).
Conclusions: Scalp surface Laplacian transforms reduce
muscle power in central and peri-central leads to less than one
sixth of the brain signal, 2-3 times better signal detection than
CAR.
Significance: Scalp surface Laplacian transformations provide
robust estimates for detecting high frequency (gamma) activity,
for assessing electrophysiological correlates of disease, and also
for providing a measure of brain electrical activity for use as a
‘standard’ in the development of brain/muscle signal separation
methods.
Description
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Keywords
Citation
Fitzgibbon SP, Lewis TW, Powers DM, Whitham EW, Willoughby JO, Pope KJ. Surface Laplacian of central scalp electrical signals is insensitive to muscle contamination. IEEE Transactions on Biomedical Engineering. 2013 Jan;60(1):4-9.