MEGEEG

MEGEEG is the integrated use of magnetoencephalography (MEG) and electroencephalography (EEG) to study brain activity. In many labs and clinics, MEG and EEG are recorded simultaneously to exploit their complementary strengths, providing high temporal resolution data and enabling more accurate localization of neural sources than either modality alone.

MEG measures the magnetic fields generated by postsynaptic currents in cortical neurons, while EEG records electrical potentials on the scalp. MEG is particularly sensitive to tangential sources in the cortex and is less distorted by the skull and scalp, whereas EEG captures a broader range of sources, including radial activity and deeper structures to some extent.

Data collection typically occurs in a magnetically shielded room with an MEG system of superconducting sensors (often sensor helmets) alongside an EEG cap with electrodes. Simultaneous recordings require careful artifact suppression for eye movements, muscle activity, and cardiac signals, followed by co-registration with structural MRI and advanced source localization methods such as dipole fitting or beamforming.

In clinical practice, MEGEEG is used for presurgical localization of epileptogenic zones and for mapping eloquent cortex involved in language and motor function. In research, it supports studies of perception, cognition, and neural dynamics with millisecond precision, and can contribute to brain-computer interface development and neurophysiological models of brain networks.

Limitations include high cost and technical complexity, limited availability outside specialized centers, and residual uncertainties in deep or highly folded regions. While MEG provides precise timing, spatial localization remains imperfect and depends on modeling assumptions, co-registration quality, and clean data.