Magnetoencephalography (MEG) is a functional neuroimaging technique that detects brain activity in real time by monitoring changes in the magnetic fields generated by the propogation of action potentials down the axons and dendrites of neurons.

MEG is a non-invasive technique that has several advantages over other functional neuroimaging techniques such as Positron Emission Tomography (PET), functional Magnetic Resonance Imaging (fMRI), Electroencephalogram (EEG), etc. First, it can detect very small areas (milimeters across) of activation in the brain. It also does not rely on the use of radioactive materials like some other techniques.

MEG differentiates itself from neuroimaging techniques such as Magnetic Resonance Imaging (MRI) and Computer axial Tomography (CT or CAT) which image brain structure rather than brain function.