Handling Artifacts in BESA

Module information
Modules	BESA Research Basic or higher
Version	5.2 or higher

It is important to get good templates for the topographies of the artifact using pattern search and averaging. Then the topographies can be used as spatial components during source analysis to separate brain from artifactual activities (preferred method).

For this load the data segments and the averaged artifacts into the source analysis module and use the PCA on the artifacts to add spatial components to the solution.

The second method is based on subspace projection which regressed the artifact topographies out and distorts the topographies during source analysis. Use the artifact correction of the on-going EEG, average and save the corrected averages. When reopening a corrected average file, artifact correction coefficients will be read and automatically used (only in BESA 5.0) for subspace projection of the data prior to source analysis. In the source analysis module, the forward vectors will be subspace projection and (similarly) distorted.

The advantage of the first, preferred method is that the source waveform of the artifact and brain signals can be compared to see the epochs of critical interference. Maps are not distorted. The artifact correction of the on-going EEG (second method) contrast the artifact against the background EEG rhythms but not against the much smaller evoked response components to be averaged.