MEG (Magnetoencephalography) Program

Electromagnetic neural source imaging

The quantitative analysis of MEG/EEG sensor data is a source of vast possibilities to characterize time-resolved brain activity. Some studies however may require a more direct assessment of the anatomical origins of the effects detected at the sensor level. It is also likely that some effects may not even be revealed using scalp measures, because of severe mixing and smearing due to the relative large distance from sources to sensors and volume conduction effects.

Electromagnetic source imaging addresses this issue by characterizing these latter elements (the head shape and size, relative position and properties of sensors, noise statistics, etc.) in a principled manner and by suggesting a model for the generators responsible for the signals in the data. Ultimately, models of electrical source activity are produced and need to be analyzed in a multitude of dimensions: amplitude maps, time/frequency properties, connectivity, etc., using statistical assessment techniques. The rest of this chapter details most of the steps required, while skipping technical details, which can be found in the references cited.