[FieldTrip] combining magnetometers and planad gradiometers for analysis

[michael.wibral at web.de]

dear neuromag / fieldtrip community,

just a small question so I can keep up with the dsicussion:
I thought that (t)SSS would nor project in a classical sense, i.e. for activities from inside the head leadfields would not have to be corrected? at least this I have read on the neuromeg list. So in most respcts the data should be treated just like rawdata - with standard coil positions after the motion correction ?

maybe someone can shed more light on this?

michael 

-----Ursprüngliche Nachricht-----
Von: "Alexandre Gramfort" <alexandre.gramfort at inria.fr>
Gesendet: 03.06.11 15:30:25
An: "Email discussion list for the FieldTrip project" <fieldtrip at donders.ru.nl>
Betreff: Re: [FieldTrip] combining magnetometers and planad gradiometers for analysis

>Hi everyone,
> 
> > I don't know enough about the elekta-software/mne-software to know what is
> > happening to the data when the ssp vectors are computed, but once we know
> > enough details it should be straightforward to build it into fieldtrip.
> 
> SSP vectors are stored in fif files and applied to data only if requested.
> 
> In a typical MNE workflow, the SSP vectors are no directly applied to the raw
> file (avoid data duplication on disk) but rather to the noise covariance matrix
> and consequently in the whitening matrix. When computing an inverse solution,
> the whitening matrix is used on the data and the lead field, hence taking
> into account the SSP vectors.
> 
> Hope this helps.
> 
> -- 
> Alexandre Gramfort, PhD
> gramfort at nmr.mgh.harvard.edu
> Dept. of Radiology MGH Martinos Center / Harvard Medical School
> http://www-sop.inria.fr/members/Alexandre.Gramfort/
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>
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