This is a teaching-oriented post about the fundamental concepts underlying electroencephalography (EEG), and to some extent magnetoencephalography (MEG). I explore how electromagnetic fields are generated from neuronal current dipoles, and how the orientation and spatial coherence of these dipoles is critical for detecting brain activity with scalp electrodes or magnetometers. I also introduce the concept of volume conduction, and consider how the distribution of electric currents across multiple tissue types might be simulated — and how cortical morphology complicates efforts to localize M/EEG sources in the human brain.
#22
