LORETA can be done in a few ways… as a source analysis for the entire EEG or segment being analyzed… or after a decomposition into the ICA components… The later will provide a better estimate of generators of the
individual components which are all blended for the overall LORETA, distorting the sources with other sources.
There is an on-going dispute regarding de-artifacting methods used in qEEG. Though there are vested interests counseling against the use of modern techniques to remove artifact while leaving the underlying EEG intact, there are also those who have specialized in the area that can provide a detailed reply to the vested interests. Just such a reply was posted recently in a commercial list server, and we got the author’s permission to re-post the discussion on the qEEGSupport.com website in a non-commercial publicly accessible form for all to see.
It specifically points to the fact that the phase changes seen are due to removal of artifact, not the distortion of the underlying EEG, which has residual subtle artifacts remaining if processed with classical approaches.
If you cut time segments out of the EEG to remove artifacts, you also remove the underlying connectivity information, splicing discontinuous microstates together destroys the underlying time series.
In the give and take of the real world of neuroscience, the need to provide a valid time-series showing the connectivity of the neural networks, yet free of artifact, is driving the need to switch to more modern techniques than snipping out segments of time. If you want to distort the timeline of the EEG (phase) just cut and paste lots of EEG together in one second chunks.
The neuroscience community will undoubtedly continue to discuss these issues, but the need for clean valid EEG is driving the field to these newer techniques, and they are performing well under the scrutiny.
Jay Gunkelman
Many have heard experts in the neurofeeback field state vehemently that the “ICA deartifacting ruins the EEG”, and that “remontaging to a Laplacian montage ruins coherence”. There are internet tutorials attempting to support these opinions. This self-publication on-line on a commercial site is not the same as peer review, and many publish bad opinions without an alternative approach even considered.
Rather than engage in the meaningless back and forth of mere opinions, I thought it was better to wait for the decision of the jury.. a jury of our peers inherent to the peer reviews in professional publications seen in the field of neuroscience. I comfortably accept the judgment of the field’s journal’s editors.
Harvard’s famous Electroencephalographer, Frank Duffy M.D. just published a large scale well designed study. Some of the key aspects in the paper are highlighted and discussed below:
“Remaining eye blink and eye movement artifacts, which may be surprisingly prominent even during the eyes closed state, were removed by utilizing the source component technique [42, 43] as implemented in the BESA (BESA GmbH, Freihamer Strasse 18, 82116 Gräfelfing Germany) software package”