[biomag] paper announcement

Tom Holroyd (NIH/NIMH) [E] tomh at KURAGE.NIMH.NIH.GOV
Thu Aug 20 21:16:19 CEST 2009

Rolando GRAVE wrote:
> Dear Colleagues,
> We would like to call your attention to the recent publication:
> http://www.hindawi.com/journals/cin/2009/656092.html
> EEG/MEG Source Imaging: Methods, Challenges, and Open Issues
> by:
> Katrina Wendel, Outi Väisänen, Jaakko Malmivuo, Nevzat G. Gencer, Bart
> Vanrumste, Piotr Durka, Ratko Magjarević, Selma Supek, Mihail Lucian
> Pascu, Hugues Fontenelle and Rolando Grave de Peralta Menendez

>>From the paper:

2.2. Things to Avoid


(1) Baseline correction. Varying the values of individual electrodes either by “arbitrary” baseline shifting or by scaling factors changes the surface maps and thus the estimated sources. Although linear inverse solutions are rather stable (continuity with respect to the data), the application of base line correction to two conditions (that will be compared on the basis of their sources) can produce artificial differences induced by the correction and not by the real sources.

	I disagree. Radial gradiometers, as used in CTF MEG systems, have an arbitrary baseline that MUST be removed.

(3) The use of very high density of sensors might also jeopardize the source analysis due to different kinds of noise at different sensors. Moreover, no significant information is added after approximately 128 electrodes due to the noise levels. Lastly, some sensors might measure more artifacts than others due to their location near active muscles.

	You're talking EEG only again. Stop saying EEG/MEG when you only know about EEG. Adding sensors to an
	MEG system _increases_ spatial resolution.

Dr. Tom
I would dance and be merry,
Life would be a ding-a-derry,
If I only had a brain.
        -- The Scarecrow

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