[FieldTrip] Create BEM model for EEG source localisation

[jan-mathijs schoffelen]

Hi Maria,

You could have a look at:

http://fieldtrip.fcdonders.nl/tutorial/headmodel

and

http://fieldtrip.fcdonders.nl/example/create_bem_headmodel_for_eeg

Hopefully this will give you some inspiration.

Best,

Jan-Mathijs

On Mar 26, 2012, at 6:01 PM, Maria Pefkou wrote:

> Dear FieldTrip users,
> 
> I started using the toolbox fairly recently to analyse EEG data and I have huge trouble making a BEM model, which I need for source localisation.
> Following the online tutorial, I processed my subjects' individual structural MRIs in FreeSurfer and MNE and managed to prepare the triangulated mesh. However, my problem is the volume conduction model. I can get a singleshell one, using the ft_prepare_singleshell function, but as far as I understand it is excusively used for MEG data. I came to this conclusion because when I try to compute the forward model, given that I provide information about the electrodes position, I always get the following error: 
> 
> "unsupported volume conductor model for EEG".
> I guess this is because the vol.type is 'nolte' and there is no such case for EEG data, at least not in the ft_prepare_vol_sens.m function, which is automatically called.
> 
> I have tried to prepare a BEM model using the ft_prepare_headmodel function with cfg.method='bemcp' or cfg.method='dipoli' but I was unsuccessful.
> The problem is that, after having tried various functions/options, I lost the general picture and I'm running in circles... The question is: I have a segmented mri, how can I get a BEM model out of this? I must be missing a fundamental part of the procedure but I can't quite find out what it is.
> Any suggestions/help would be very much appreciated.
> 
> Thank you in advance,
> Maria Pefkou
> 
> ------------------------------------------
> Research Assistant
> Functional Brain Mapping Lab
> University of Geneva
> 
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Jan-Mathijs Schoffelen, MD PhD 

Donders Institute for Brain, Cognition and Behaviour, 
Centre for Cognitive Neuroimaging,
Radboud University Nijmegen, The Netherlands

Max Planck Institute for Psycholinguistics,
Nijmegen, The Netherlands

J.Schoffelen at donders.ru.nl
Telephone: +31-24-3614793