Editing Magnetoencephalography (section)

=== Dipole model source localization ===
A widely accepted source-modeling technique for MEG involves calculating a set of equivalent current dipoles (ECDs), which assumes the underlying neuronal sources to be focal. This dipole fitting procedure is non-linear and over-determined, since the number of unknown dipole parameters is smaller than the number of MEG measurements.<ref>{{cite journal | vauthors = Huang MX, Dale AM, Song T, Halgren E, Harrington DL, Podgorny I, Canive JM, Lewis S, Lee RR | title = Vector-based spatial-temporal minimum L1-norm solution for MEG | journal = NeuroImage | volume = 31 | issue = 3 | pages = 1025–37 | date = July 2006 | pmid = 16542857 | doi = 10.1016/j.neuroimage.2006.01.029 | s2cid = 9607000 | url = https://escholarship.org/uc/item/4xr5z4qd }}</ref> Automated multiple dipole model algorithms such as [[multiple signal classification]] (MUSIC) and multi-start spatial and temporal modeling (MSST) are applied to the analysis of MEG responses. The limitations of dipole models for characterizing neuronal responses are (1) difficulties in localizing extended sources with ECDs, (2) problems with accurately estimating the total number of dipoles in advance, and (3) dependency on dipole location, especially depth in the brain.