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OBJECTIVE: Validate independent component analysis (ICA) for removal of EMG contamination from EEG, and demonstrate a heuristic, based on the gradient of EEG spectra (slope of graph of log EEG power vs log frequency, 7-70 Hz) from paralysed awake humans, to automatically identify and remove components that are predominantly EMG. METHODS: We studied the gradient of EMG-free EEG spectra to quantitatively inform the choice of threshold. Then, pre-existing EEG from 3 disparate experimental groups was examined before and after applying the heuristic to validate that the heuristic preserved neurogenic activity (Berger effect, auditory odd ball, visual and auditory steady state responses). RESULTS: (1) ICA-based EMG removal diminished EMG contamination up to approximately 50 Hz, (2) residual EMG contamination using automatic selection was similar to manual selection, and (3) task-induced cortical activity remained, was enhanced, or was revealed using the ICA-based methodology. CONCLUSION: This study further validates ICA as a powerful technique for separating and removing myogenic signals from EEG. Automatic processing based on spectral gradients to exclude EMG-containing components is a conceptually simple and valid technique. SIGNIFICANCE: This study strengthens ICA as a technique to remove EMG contamination from EEG whilst preserving neurogenic activity to 50 Hz.

Original publication

DOI

10.1016/j.clinph.2015.12.009

Type

Journal article

Journal

Clin Neurophysiol

Publication Date

03/2016

Volume

127

Pages

1781 - 1793

Keywords

Alpha rhythms, Electroencephalogram, Electromyogram, Neuromuscular paralysis, Oddball, Photic stimulation, Steady state responses, Acoustic Stimulation, Adolescent, Adult, Aged, Aged, 80 and over, Child, Electroencephalography, Electromyography, Female, Humans, Male, Middle Aged, Paralysis, Photic Stimulation, Principal Component Analysis, Young Adult