[FieldTrip] fieldtrip Digest, Vol 119, Issue 14

[RICHARDS, JOHN]

Jan-Mathijs (or others)

Thanks for your answers.  I still have one question to be answered.

If we use the method where we do the SVD step on the filter, then calculating the source elements from any dataset will use the same projection orientation.  

What is the rationale for including the COV in the filter*COV*filter'?    Does this intend to modify the orientation by the directionality of the  noise?  This makes sense to me if this is an ERP experiment.  I have used this in various FT functions by choosing the prestimulus as a baseline for noise and the COV is from the prestimulus; then use the resulting filter (filter * COVprestimulus * filter') for the source analysis of the stimulus data.   However, in the current analysis we are doing we have a continuous EEG context--don't really have a baseline for estimation the noise.  We also have several conditions and different transformations of the data before the source calculation.  What would we be gaining by adding the svd(filter*COV*filter') step to the SVD, over just using the svd(filter)?  I think the crux of my question is what is being accomplished by using the COV in the projection calculation?

Thanks for your help.

John

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John E. Richards
Carolina Distinguished Professor
Department of Psychology
University of South Carolina
Columbia, SC  29208
Dept Phone: 803 777 2079
Fax: 803 777 9558
Email: richards-john at sc.edu
https://jerlab.sc.edu
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