Baillet S. Electromagnetic Brain Mapping using MEG-EEG Theory 2011

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Electroencephalography (EEG) and magnetoencephalography (MEG) are techniques dedicated to the non-invasive detection of neural current ows through the electromagnetic eld they generate and that can be measured outside the head. Though MEG and EEG were born in physics and electro-physiology laboratories several decades ago, they have constantly evolved by integrating new technological and methodological advances. In the neuropsy-chology lab, EEG has rapidly been adopted as a technique to investigate the timing and scalp topography of specic brain responses elicited by a stimulus. Today, MEG and EEG set-ups integrate from several dozens to hundreds of sensors distributed outside the head, which once combined with models of electromagnetics within brain and head tissues allow the estimation of the neural generators of thesèbrain waves'. This has given rise to techniques for time-resolved electromagnetic brain mapping, which this chapter reviews in more details with a pragmatic standpoint, and an emphasis on the exper-imental benets of accessing brain activation at the millisecond time scale