Magnetoencephalography (MEG) *

Magnetoencephalography (MEG) measures noninvasively minute magnetic fields produced by neuronal activity of the brain. In electroencephalography (EEG), a voltage distribution produced by neuronal currents is measured with scalp electrodes whereas in MEG neuronal activity is detected by superconducting sensors measuring the corresponding magnetic fields outside the head. Source modelling is used in MEG to model, quantify, and localize sources contributing to the measured magnetic fields at ms temporal resolution and a few mm spatial resolution. Skull, cerebrospinal fluid, and scalp are transparent to magnetic fields. MEG is optimally suited for detecting neuronal dynamics in the cerebral cortex. The first whole-head commercial MEG systems were introduced in the early 90’s. At present, MEG systems are widely used in hospitals and academic research infrastructures. The potential clinical and research uses include for example studies of the functions of neural oscillations, the nature of event-related brain activation, mechanisms of functional connectivity between regions and the emergence of modes of network communication in brain systems. MEG has two clinical applications related to the localizations of epileptic foci and mapping functionally important regions in the brain prior to surgery. (Baillet S., Nature Neuroscience 2017, 20, 327-339; Hari R. et al., Clinical Neurophysiology 2018, 129, 1720-1747; Gross J., Neuron 2019, 104, 189-204).