Beamforming with reference channels

[sharon riwkes]

Dear Jan-Mathijs,
Thanks for your quick answer!
I will check the different possibilities. I think that the problem was in
the stage the lead field computation.
And yes, this is 4D data.
Sharon.

On Mon, Aug 2, 2010 at 4:23 PM, jan-mathijs schoffelen <
jan.schoffelen at donders.ru.nl> wrote:

> Hi Sharon,
>
> If the results are exactly the same, I guess the references have not been
> taken into account at all. Although it remains to be seen whether you gain a
> lot with this approach (my preferred alternative would be to clean the data
> from external noise using the references and taking into account the
> correction in the forward computation), it should be possible to do it in
> fieldtrip. To get it to work, you have to check whether the necessary
> information is present throughout your analysis pipeline. Importantly, when
> computing the covariance matrix in ft_timelockanalysis, you have to include
> the references. The same goes for the computation of the leadfields (if you
> use ft_prepare_leadfield for that). If this information is still present
> prior to your call to ft_sourceanalysis, you may want to check whether you
> have to specify cfg.channel (to include the references, rather than 'MEG'
> (which may be the default, and causes selection of close-to-the-head sensors
> only).
> Just for the record: is it 4D-neuroimaging data you are working on?
>
> Best wishes,
>
> Jan-Mathijs
>
>
> On Aug 2, 2010, at 2:06 PM, sharon riwkes wrote:
>
> Hi all,
> I tried to do source localization, after beamforming with the LCMV method.
> I did it once for all the MEG channels, and once for MEG channels *AND the
> reference channels*. I was hoping that using the reference channels will
> improve the localization by ignoring noise coming from outside of the brain.
>
> However, I got the *exact same results for MEG+reference channels* as *for
> MEG alone!*
> Does anyone know how to include the reference channels effectively in the
> LCMV beamforming?
> Thanks for your help,
> Sharon Riwkes.
>
> ----------------------------------
>
> The aim of this list is to facilitate the discussion between users of the
> FieldTrip toolbox, to share experiences and to discuss new ideas for MEG and
> EEG analysis.
>
> http://listserv.surfnet.nl/archives/fieldtrip.html
>
> http://www.ru.nl/fcdonders/fieldtrip/
>
>
> Dr. J.M. (Jan-Mathijs) Schoffelen
> Donders Institute for Brain, Cognition and Behaviour,
> Centre for Cognitive Neuroimaging,
> Radboud University Nijmegen, The Netherlands
> J.Schoffelen at donders.ru.nl
> Telephone: 0031-24-3668063
>
> ----------------------------------
>
> The aim of this list is to facilitate the discussion between users of the
> FieldTrip toolbox, to share experiences and to discuss new ideas for MEG and
> EEG analysis.
>
> http://listserv.surfnet.nl/archives/fieldtrip.html
>
> http://www.ru.nl/fcdonders/fieldtrip/
>

----------------------------------
The aim of this list is to facilitate the discussion between users of the FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/neuroimaging/fieldtrip.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.science.ru.nl/pipermail/fieldtrip/attachments/20100804/c0bfe74e/attachment-0001.html>