[FieldTrip] ft_dipolefitting and CTF 3rd order gradient compensation

[Schoffelen, J.M. (Jan Mathijs)]

See line 187 in ft_compute_leadfield. More information can be found in ctf2grad and ft_denoise_synthetic.

Best,
Jan-Mathijs

On Feb 19, 2016, at 1:20 AM, François Tadel <francois.tadel at mcgill.ca> wrote:

> Hello,
> 
> When estimating dipoles with ft_dipolefitting:
> How should I proceed if I want to pass the information about the 3rd order gradient compensation to the computation of the forward model ?
> Is there a field I should fill either in the data or the cfg structure?
> 
> We are trying to compare the goodness of fit obtained with Brainstorm, MNE and FieldTrip (simple CTF electric phantom recordings). They are calling the FieldTrip function from the Brainstorm environment and asked me to check what was the situation with the CTF compensation matrix. I was expecting to find something like the line below in the code, but couldn't find it:
> 
>    Gain(iMeg,:) = Gain(iMeg,:) - MegRefCoef * Gain(iRef,:)
> 
> % iMeg = indices of the MEG channels
>    %iRef = indices of the CTF MEG reference channels
>    % Gain = leadfield matrix [Nchannels x Nsources]
>    % MegRefCoef= 3rd order compensation matrix [Nchannels_meg x Nchannels_ref]
> 
> Can someone help me with this?
> 
> Thanks,
> Francois
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