Intracranial Validation of Magnetoencephalography Across Oscillatory Frequency and Depth

Functional neuroimaging methods like functional magnetic resonance imaging, electroencephalography (EEG), and magnetoencephalography (MEG) play a vital role in understanding human cognition. MEG, in particular, can record the magnetic fields generated by electrical currents within the brain from outside the skull, providing insights into neural activity at its intrinsic timescale.

Recently, optically pumped magnetometers (OPMs) have made it possible to conduct these recordings in more naturalistic settings and for previously inaccessible populations, leading to a growing adoption of MEG.

However, the extent to which MEG recordings can capture different features of neural activity remains unclear. To investigate this, researchers utilized a unique dataset consisting of concurrent MEG and intracranial EEG recordings from epileptic patients. The findings revealed that group-level inferences of spontaneous oscillatory dynamics made using source-localized MEG, which estimate power and bursts, accurately reflected the underlying neural activity.

This accuracy was observed for lower-frequency activity, such as delta, theta, and alpha bands, as well as for superficial sources. The agreement was weakest in the gamma range.

Interestingly, MEG was also sensitive to deep structures, including the hippocampus. It captured oscillatory power and burst dynamics in the theta band, most robustly in this region. These results demonstrate that MEG can detect physiologically meaningful activity in both cortical and subcortical regions, establishing a foundation for interpreting future MEG studies across various research domains.