The human magnetoencephalogram: some EEG and related correlations.

Simultaneous magnetoencephalographic (MEG) and electroencephalographic (EEG) data were recorded from six normal adult subjects. MEG signal strength and EEG voltage level appear to be linearly correlated. Spectral analysis suggested that the MEG and EEG data were produced by similar but non-identical generator systems. A vertex region magnetic averaged evoked response to flash was recorded in one (of four) subjects, consisting of a waveform similar to but out of phase with the simultaneous EEG averaged evoked response, such that cortical negativity was correlated with a magnetic field directed into the scalp. Eye movement artifact, which can seriously compromise EEG recordings, does not appear to be a major problem in MEG recordings.