[FieldTrip] EEG forward solution

Maris Skujevskis icelandhouse at gmail.com
Wed Aug 5 19:23:20 CEST 2015


Hi all,

I am working on constructing a forward model for source reconstruction
using minimum-norm estimate.
There are two tutorials on EEG forward solutions:
http://www.fieldtriptoolbox.org/tutorial/headmodel_eeg
http://www.fieldtriptoolbox.org/tutorial/minimumnormestimate
Each uses a somewhat different set of functions for calculating the source
model and the volume conduction model but it is not clear whether these
differences are real (i.e. yielding different outcomes) or only apparent
(i.e. different ways of reaching the same result).

Specifically, my question is:

if I follow the tutorial
http://www.fieldtriptoolbox.org/tutorial/headmodel_eeg , all the way to the
line...

vol                    = ft_prepare_headmodel(cfg, bnd);

...to which I then add...:

%source model
cfg                   = [ ];
cfg.mri             = mri_of_subject;
sourceModel   = ft_prepare_sourcemodel(cfg);

% lead field
cfg                  = [ ];
cfg.vol            = vol;
cfg.elec          = electrode_positions;
cfg.grid          = sourceModel;
leadfield        = ft_prepare_leadfield(cfg);

...will this give me the same leadfield as the procedure outlined in
http://www.fieldtriptoolbox.org/tutorial/minimumnormestimate ?

If these are both valid ways of calculating the leadfield, but they do not
yield equivalent results, what - in general - should be my considerations
when choosing between the two?

Thanks!
Maris
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