[FieldTrip] [Fieldtrip] dipole-fitting problem

[Max T.]

Dear all,

I am new to fieldtrip and I currently tried to do a simple dipole fit
on EEG data using a four-shell headmodel. The data consists of 96
trials which I preprocess and average through fieldtrip, then I do the
dipole fit using two symmetric dipoles. As I only wanted to try out
the fitting-capabilities of fieldtrip, I skipped artifact detection
etc. The problem I encountered is that the fitting results from
fieldtrip vastly differ from results that come from BESA, the dipoles
have totaly different positions.

May this be caused by the different algorithms of FT and BESA? Or must
there be something wrong with my script? Besides this, does FT have
capabilities to plot source-level data using the method 'surface' if
there's no individual MRI available?

This is what my script looks like:

cfg = [];
cfg.dataset = 'data.cnt';
cfg.trialdef.eventtype = 'trigger';
cfg.trialdef.eventvalue = 1;
cfg.trialdef.prestim = 0.5;
cfg.trialdef.poststim = 1;
cfg = ft_definetrial(cfg);

cfg.channel=1:30;
cfg.demean = 'yes';
cfg.baselinewindow = [-0.1 0];
data = ft_preprocessing(cfg);
avg = ft_timelockanalysis(cfg,data);

vol.o = [0 0 0];
vol.c = [0.3300 1 0.0042 0.3300];
vol.r = [0.84 0.85 0.92 1];
elec = ft_read_sens('electrodes.sfp');
cfg.numdipoles = 2;
cfg.symmetry = 'x';
cfg.channel = 1:30;
cfg.elec = elec;
cfg.vol = vol;
cfg.gridsearch = 'yes';
cfg.grid.resolution = 1;
cfg.model = 'regional';
cfg.latency = [0.07 0.08];
cfg.channel = 'all';
dipol = ft_dipolefitting(cfg,avg);

Thanks in advance
Max Taubert