NeuroSpin's platforms provide researchers with a measurement device that enables the use of Magnetoencephalography (MEG) technology.

Magnetoencephalography (MEG) records the magnetic activity of the brain. Electromagnetic signals originate in the way information travels through the neural system: neurons communicate with each other through local electrochemical changes that propagate along their membranes and accumulate at synapses. In populations or assemblies of neurons, these changes give rise to electric currents, and therefore necessarily to magnetic fields. Thus, on a large scale, the magnetic fields recorded with the MEG come from the synchronous electrical activity of tens of thousands of neurons. Nevertheless, these fields remain very weak, of the order of femtotesla (1 fT = 10 -15 T), one billion times smaller than the terrestrial magnetic field, whose value is close to 50 microteslas (1 μT = 10 - 6 T). MEG therefore uses very sensitive sensors called SQUIDs (Superconducting Quantum Interference Devices), based on the superconducting properties of Josephson junctions. The MEG is placed in a shielded chamber and isolated by a mu-metal (nickel and iron alloy) to filter surrounding electromagnetic noise.

 

The main quality of the MEG lies in its ability to observe the brain processes to the millisecond, in a non-invasive way. The recorded signals provide relevant information on the temporal course of brain activity and thus make it possible to record and understand the live neural "language". Using advanced inverse problem solving methods, the origin of MEG signals can be localized to within a few tens of millimeters, based on the anatomical MRI of an individual. The MEG has proved its clinical utility in the detection of epileptic foci, but also allows and above all to question the neural bases of the major human cognitive functions.