Magnetoencephalography (MEG)

Magnetoencephalography (MEG).
Magnetoencephalography (MEG) is a non-invasive technique used to measure magnetic fields generated by small intracellular electrical currents in neurons of the brain. Thus MEG provides direct information about the the dynanamics of evoked and spontaneous neural activity and the location of their sources in the brain.
MEG and EEG are closely related, the latter detecting the electric potentials generated by neural currents instead of the corresponding magnetic fields. However, it turns out that the task of inferring the sites of brain activation is often more straightforward from MEG than from EEG. This is due to the electric and magnetic properties of the tissues in the cranium and also to the fact that MEG is selectively sensitive to currents flowing tangential to the scalp, corresponding to sulcal activations. On the other hand, the interpretation of EEG is often complicated by the simultaneous presense of both sulcal and gyral sources, the latter corresponding to radial currents.