Magnetoencephalography (MEG) and electroencephalography (EEG) measure non-invasively the weak electromagnetic signals induced by neural currents. While the more common neuroimaging method of functional magnetic resonance imaging (fMRI) provides volumetric images defined over voxel grids using a sampling rate of around one image per second, M/EEG captures both slowly and rapidly changing dynamics of brain activations at a millisecond time resolution. This enables the investigation of neuronal activity over a wide range of frequencies that can offer potentially complementary insights regarding how the brain works as a large system (Tallon-Baudry et al., 1997; Fries, 2009).
