Glossary

The Glossary provides short definitions of vocabulary specific to EEG and general neuroimaging concepts. Many entries are taken from MNE-Python.

anatomical landmark

anatomical landmarks

fiducial

fiducial point

fiducial points

Fiducials are objects placed in the field of view of an imaging system to act as known spatial references that are easy to localize. In neuroimaging, fiducials are often placed on anatomical landmarks such as the nasion (NAS) or left/right preauricular points (LPA and RPA).

These known reference locations are used to define a coordinate system for localizing sensors (hence NAS, LPA and RPA are often called “cardinal points” because they define the cardinal directions of the head coordinate system). The cardinal points are also useful when co-registering measurements in different coordinate systems.

Due to the common neuroimaging practice of placing fiducial objects on anatomical landmarks, the terms “fiducial”, “anatomical landmark”, and “cardinal point” are often (erroneously) used interchangeably.

BEM

boundary element model

boundary element method

BEM is the acronym for boundary element method or boundary element model. Both are related to the definion of the conductor model in the forward model computation. The boundary element model consists of surfaces such as the inner skull, outer skull, and outer skin (scalp) that define compartments of tissues of the head.