[FieldTrip] Fitting dipole to a topography
Tzvetan Popov
tzvetan.popov at uni-konstanz.de
Wed Aug 26 08:27:31 CEST 2015
Dear Ksenia,
I would first start with the organization of the data in a format FieldTrip can sense.
data = [];
data.trial ={[chan x time]} % this is your elec x topography matrix, where topography is observed on consecutive time points
data.time = [vector-number of time points];
data.label = {‘elec1’,’elec2’ etc.} your electrode labels
data.elec = this is key reflecting the position of the electrodes relative to the head
Next, you have to compute a volume conduction model. How to do so is explained here: http://www.fieldtriptoolbox.org/tutorial/headmodel_eeg?s[]=eeg&s[]=volume&s[]=conduction&s[]=model
After this you can proceed with the dipole fitting which is explained for instance here: http://www.fieldtriptoolbox.org/tutorial/natmeg/dipolefitting#fit_a_dipole_model_to_the_meg_data
Under cfg.latency you could specify the number of the topography you are interested in and under cfg.vol the BEM model you computed in the previous step. If you don#t have individual MRI
you can use the standard BEM model located in the ~template/headmodel/standard_bem.mat. Note that before you do so you should coregister the headmodel with the electrodes using
ft_electroderealign.
Good luck
tzvetan
> Dear fieldtrip users,
>
> I wonder if you can help me out. I have a relatively simple problem: having a topography matrix (where rows correspond to topographies, and columns correspond to channels) I want to fit a dipole to each topography. I have looked through tutorials and documentation and I've seen this example http://www.fieldtriptoolbox.org/example/compute_forward_simulated_data_and_apply_a_dipole_fit. Still, I can't figure out how I should use the toolbox to solve my problem.
>
> What would be the right arguments to call ft_dipolefitting with in my case? If I have EEG data, topography matrix and channel locations, what would be the easiest way to fit a dipole to each topography?
>
> Thank you in advance for any help.
>
> Ksenia Volkova
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> fieldtrip mailing list
> fieldtrip at donders.ru.nl
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