The human magnetoencephalogram: some EEG and related correlations

Area of Science:

• Neuroscience
• Biophysics

Background:

• Magnetoencephalography (MEG) and electroencephalography (EEG) are non-invasive techniques measuring brain activity.
• Understanding the relationship between MEG and EEG signals is crucial for interpreting brain function.
• Artifacts, such as eye movements, can contaminate EEG data, potentially affecting analysis.

Purpose of the Study:

• To investigate the correlation between simultaneous MEG and EEG recordings.
• To compare the generator systems producing MEG and EEG signals.
• To assess the susceptibility of MEG to eye movement artifacts compared to EEG.

Main Methods:

• Simultaneous MEG and EEG data acquisition from six healthy adult subjects.
• Linear correlation analysis of MEG signal strength and EEG voltage.
• Spectral analysis to compare signal generation.
• Averaged evoked response analysis to flash stimuli.

Main Results:

• A linear correlation was observed between MEG signal strength and EEG voltage levels.
• Spectral analysis indicated that MEG and EEG data originate from similar, yet distinct, generator systems.
• A vertex magnetic evoked response was recorded, out of phase with the EEG response, correlating cortical negativity with inward scalp magnetic fields.
• Eye movement artifacts, problematic for EEG, were found to be a minor issue for MEG.

Conclusions:

• MEG and EEG signals are linearly correlated and reflect similar neural generators.
• MEG shows potential advantages over EEG due to reduced susceptibility to eye movement artifacts.
• Further research can leverage simultaneous MEG-EEG to better understand brain activity and overcome limitations of individual techniques.