[FieldTrip] Solution to the EEG forward problem

Jose Antonio Urig├╝en juriguen at gmail.com
Fri Mar 14 12:23:22 CET 2014


Dear all


This may be simple to answer, since I am quite new to the area and keep
struggling with the tutorials at the main website. So here we go:

I want to use Fieltrip in Matlab (Windows) to:


1. Compute the leadfield at a set of electrodes positioned in the scalp
based on a BEM model of the head (something along the line of
http://fieldtrip.fcdonders.nl/tutorial/headmodel_eeg plus correct use of
the ft_prepare_leadfield function)

So, what is confusing me is that say I have a head model / volume and the
set of electrodes (result of following
http://fieldtrip.fcdonders.nl/tutorial/headmodel_eeg ), then if I do


*pos = [0 0 0.5];*


*cfg = [];*

*cfg.grid.pos = pos;*
*gridp = ft_prepare_sourcemodel(cfg, vol, elec_aligned);*

*cfg = [];*
*cfg.vol  = vol;*
*cfg.elec = elec_aligned;*
*cfg.grid = gridp;*
*grid = ft_prepare_leadfield(cfg);*

*lf_openmeeg = grid.leadfield{1};*

I get the leadfield at the electrode locations. However, how do I get the
actual potential at the electrodes if, say, I have dipole magnitudes and
moments. Is the solution simply

V = *lf_openmeeg * (magnitudes * moments)*

*??*


2. Can I use Fieltrip to obtain a set of simulated EEG channels with brain
rhythms? I was thinking of using available waveforms from the internet of
intracraneal recordings as one of the inputs, however I woudl still need
dipole positions / orientations (moments).

Any ideas how to do this?


Thanks in advance
Toni
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