[FieldTrip] template brain/standard EEG-Electrodes

Lydia Elshoff aglaia.jankoli at gmx.de
Thu Mar 17 10:47:48 CET 2011


Hi Nathan!
THank you very much -we┬┤ll try that out and I hope it will work.

Greets, Lydia


-------- Original-Nachricht --------
> Datum: Thu, 17 Mar 2011 08:46:50 +0100
> Von: Nathan Weisz <nathanweisz at mac.com>
> An: Email discussion list for the FieldTrip project <fieldtrip at donders.ru.nl>
> Betreff: Re: [FieldTrip] template brain/standard EEG-Electrodes

> hi,
> 
> somewhere on the firledtrip FTP there is a standard_BEM. i got mine from
> EEGlab, but it's fieldtrip stuff. it's ~11 MB so i won't send it over the
> list :-)
> 
> anyway: this is a headmodel created by segmentation of a MNI-brain. if you
> follow the fieldtrip tutorial on DICS this contains the "vol"-structure
> you need.
> the only - and sometimes not trivial - issue you have is to get your
> electrodes aligned / co-registered onto the head surface. you have different
> options (i guess you don't have individual MRIs otherwise you wouldn't be
> asking), e.g.:
> - there are standard electrode positions in MNI space for 10/05 electrode
> placements somewhere in fieldtrip. you may find all / most electrodes of
> you EEG in this file. that's fast and no headache.
> - your EEG vendor may have such a file specific for your cap. we got one
> from our EEG supplier (ANT). even better than the option above, because then
> you are sure to have all electrodes (especially when the cap deviates from
> 10/20 or 10/05 placement).
> - digitize the electrode-positions in one subject and co-register it to
> the MNI template brain manually. this option is probably a pain since the
> head of any individual you choose won't fit exactly the MNI template. so you
> will have to play around until the electrodes are as much as possible on the
> head surface. [unless: if you can also get an MRI for that subject: then
> co-register electrodes with individual MRI; normalize individual MRI to
> MNI-template; take the resulting transformation matrix to recalculate your
> elec.pos field in MNI coordinates ... that would also be an easy option]
> 
> in any case once your electrode data, headmodel and MRI (latter not
> strictly needed for the sourceanalysis, but you will want it for visualization)
> are in the same coordinate sytsem, then you can proceed as described in the
> tutorial. there is really no difference anymore whether you have individual
> or standard stuff, i.e. the sourceanalysis won't care as long as it gets
> the structures it wants.
> 
> a word of consolation: if you want to use the standard headmodel / brain,
> then you need to solve this issue only one time :-)
> 
> good luck,
> n
> 
> 
> On 17.03.2011, at 08:12, Lydia Elshoff wrote:
> 
> > hello!
> > 
> > We are a research group at the Neuropaediatrics Department in Kiel and
> started working with EEG Analysis in fieldtrip. We now face several
> questions: Could you please tell us how to or send us a matlab code for the using
> template brain and the standard EEG-Electrodes in DICS analysis in
> fieldtrip? Or perhaps show an example???
> > Thank you very much!!!
> > 
> > Lydia Elshoff
> > -- 
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