[FieldTrip] EEG Source reconstruction: sourcespace and the volume conductor misaligned

[Stephen Politzer-Ahles]

Hello Leo,

This looks like the same problem I was having a few months ago, and there
should be some messages on the list about it. I am not able to look at my
data and scripts right now, but if I remember correctly (you can check the
lists for more) the problem had to do with the transformation matrix, and
ft_convert_units. In my case, during the "volume conduction model" step of
the tutorial (the last step before you can plot the vol and sourcespace
together), I had to add an extra

vol = ft_convert_units(vol, 'cm')

before ft_transform_geometry. I don't remember if this alone will solve the
problem (unfortunately the the situation is kind of complicated right now,
there is also a different version of the minimum norms tutorial that is
still in development--see the previous messages for links--and I think my
processing pipeline ended up being a mixture of the two to get things
working. Which means that it's hard to track where exactly I solved the
problem.)

Best,
Steve


>
> Message: 1
> Date: Sat, 28 Sep 2013 15:25:32 +0200
> From: Zizlsperger Leopold <zizlsperger at gmail.com>
> To: <fieldtrip at science.ru.nl>
> Subject: [FieldTrip] EEG Source reconstruction: sourcespace and the
>         volume  conductor misaligned
> Message-ID: <06D14B0C-655A-4EF2-A69A-B735DBDBC504 at gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi all,
> I am following the instructions in the "Source reconstruction of
> event-related fields using minimum-norm estimate" tutorial closely to do a
> source-analysis of EEG data using the example MRI. As I am following the
> tutorial almost unchanged I am not including the script here.
>
> When I re-align the volume conduction model to the sourcespace they are
> not aligned very well, see screenshot attached. I remember a similar
> question in the mailing list a while ago but cannot find it...
>
> Is there a way to interactively realign volume conduction model and
> sourcespace? Re-doing the fiducials did not change the aligment
> considerably. Also, my volume conduction model looks weird...
> I used ft_determine_coordsys on both the vol and the sourcespace, see
> screenshots attached, too.
> Would be nice if you could point me in the right direction.
> Thanks in advance.
> Leo
>
> ----
>
>
>
>
> Dr. med. Leopold Zizlsperger
> Klinik f?r Neurologie
> Uniklinik RWTH Aachen
> Pauwelsstrasse 30
> 52074 Aachen
> Tel: +49 241 80 35465
> lzizlsperger at ukaachen.de
>
> Leopold Zizlsperger, MD
> Department of Neurology
> RWTH Aachen University
> Pauwelsstrasse 30
> 52074 Aachen, Germany
> Tel: +49 241 80 35465
> lzizlsperger at ukaachen.de
>
>
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