Subcortical sources are not working (Deep Brain Tutorial)

[Raymundo.Cassani]

@tourette95

Why is not dSPM the new source standard?

It is possible to get similar results using current density maps (MN imaging) if the results are normalized, for example with z-score.

Best source localisation method: tutorial vs literature

The idea would be that normalization/standardization can be applied a posteriori, for instance after several runs are averaged at the source level. dSPM and sLORETA can also be expressed as linear kernel operators, but the issue is with the proper estimation of data covariance on single trial data: not impossible but not entirely convenient either. So in summary, we do recommend that a form of standardization be applied on source maps: this latter can be performed at different instances of the …

One advantage of using these non-normalized maps, is they can be used to reconstruct the MEG/EEG sensor time series, thing that is not possible with already standardized maps (dSPM and LORETA):

Signal simulation by dSPM unconstrained source map

Sources estimated with dSPM cannot be directly used to reconstruct the MEG/EEG signals, because the dSPM sources are the minimum-norm sources normalized to the noise in each source location. Thus at each source location the sources have been scaled in a different way, which besides removing the physical units, changes the magnitude relationship among sources, so it is not appropriated to use the forward model on these normalized sources. If you want to reconstruct the MEG/EEG signals, you could…

The similarity among normalized MN, dSPM and LORETA is showed in this link.
Moreover, recommendations on when to use each method is also provided in that section.

https://neuroimage.usc.edu/brainstorm/Tutorials/SourceEstimation#Standardization_of_source_maps