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MEG and EEG show different sensitivity to myogenic artifacts
1Institute of Neurophysiology and Pathophysiology, Univ. Klinikum Eppendorf, Hamburg, Germany. R.Zimmermann@UKE.Uni-Hamburg.de
Neurology & Clinical Neurophysiology : NCN
|July 14, 2005
Summary
Increased muscle stress significantly impacts electroencephalography (EEG) signals, not magnetoencephalography (MEG). Myogenic sources, not cortical ones, explain these EEG changes, with muscle activity contributing about 10% to spontaneous MEG signals.
Area of Science:
- Neuroscience
- Biomedical Engineering
- Signal Processing
Background:
- Simultaneous electroencephalography (EEG), magnetoencephalography (MEG), and electromyography (EMG) are crucial for understanding brain-muscle interactions.
- Differentiating myogenic artifacts from neural activity in brain signals is a persistent challenge.
Purpose of the Study:
- To investigate the impact of varying muscular stress on EEG and MEG signals.
- To differentiate between cortical and myogenic contributions to brain activity measurements.
Main Methods:
- Simultaneous EEG, MEG, and EMG recordings during conditions of higher, lower, and baseline muscular stress.
- Power spectral density (PSD) analysis across five frequency bands (theta, delta, alpha, beta, gamma).
- Correlation analysis between EEG and EMG changes; modeling of myogenic activity.
Main Results:
- Increased muscular stress led to significant increases in most EEG bands, while MEG showed no significant changes.
- EEG topographies suggested myogenic sources rather than cortical generators, confirmed by EEG-EMG correlations.
- Reduced muscular stress correlated with a significant decrease in MEG gamma activity.
- Myogenic activity was estimated to constitute approximately 10% of the spontaneous MEG signal.
Conclusions:
- EEG is highly susceptible to myogenic artifacts, especially under increased muscular stress.
- MEG signals are less affected by muscular activity, but gamma band activity can be reduced.
- Accurate interpretation of brain signals requires accounting for myogenic contributions, particularly in EEG.