Brief Presentation of MEG and EEG
Last modified on : Fri, 12 Feb 10
Electro-Encephalography (EEG) and Magneto-Encephalography (MEG) are two non-invasive techniques for measuring (part of) the electrical activity of the brain.
While EEG is an established technique (Hans Berger, a German neuropsychiatrist, measured the first human EEG in 1929), MEG is a rather new one: the first measurements of the magnetic field generated by the electrophysiological activity of the brain were done in 1968 at MIT by David Cohen. The major technical advance that allowed the practical use of MEG was the development and use of SQUIDs (superconducting quantum interference device) by Zimmerman and colleagues in 1969. This type of sensor is extremely sensitive, allowing the measurement of the very low magnetic fields (twelve orders of magnitude lower than the earth magnetic field !) induced by the functioning brain.
Nowadays, EEG is relatively inexpensive and is commonly used to detect and qualify neural activity (epilepsy detection and characterisation, neural disorder qualification, BCI, …). Comparatively to EEG, MEG is much more expensive, because SQUIDS operate in very challenging conditions: they need to be cooled down to 4K by liquid Helium, and a specially shielded chamber must be used to separate the signal of interest from the ambient noise. However, as MEG reveals a complementary vision to that of EEG, and is less sensitive to the head structure, more and more MEG machines are being installed throughout the world.
INRIA Sophia Antipolis participates in one such platform recently installed in the “La Timone” hospital in Marseille.
