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Accounting for linear transformations of EEG and MEG data in source analysis
1Centre for Integrative Neuroscience, University of Tübingen, Tübingen, Germany; MEG-Center, University of Tübingen, Tübingen, Germany.
Plos One
|April 4, 2015
Summary
Adapting the physical forward model (leadfield) is crucial for electroencephalography (EEG) and magnetoencephalography (MEG) source analysis when re-referencing or computing synthetic gradiometers, but not when removing artifactual components.
Area of Science:
- Neuroscience
- Biophysics
- Signal Processing
Background:
- Linear modifications of electroencephalography (EEG) and magnetoencephalography (MEG) sensor data are common.
- Techniques include re-referencing, synthetic gradiometer computation, and artifact removal via independent component analysis.
- The necessity of adapting the physical forward model (leadfield) for source analysis after these modifications is a key practical question.
Purpose of the Study:
- To clarify when the leadfield requires adaptation in EEG and MEG source analysis following sensor-level signal modifications.
- To differentiate between modifications requiring leadfield adaptation and those that do not.
- To illustrate the consequences of incorrect leadfield modification.
Main Methods:
- Theoretical analysis of linear signal modifications in EEG and MEG.
- Simulation and demonstration of source analysis with and without appropriate leadfield adaptation.
- Case study illustrating the impact of erroneous leadfield modification.
Main Results:
- Two distinct scenarios for leadfield adaptation were identified.
- Leadfield adaptation is necessary for re-referencing EEG and computing synthetic MEG gradiometers.
- Leadfield adaptation is not required and potentially detrimental when removing artifactual components from EEG/MEG data.
Conclusions:
- The decision to adapt the leadfield depends critically on the type of sensor-level modification applied.
- Incorrect leadfield modification during artifact removal can lead to erroneous source analysis results.
- Researchers must carefully consider leadfield adaptation procedures in EEG and MEG source analysis workflows.
