[FieldTrip] finding gradiometer

[Nathan Weisz]

Hi Ricardo,

try cfg.elec rather than cfg.grad.

also ft_freqanalysis does not "recover" electrode positions, at least that would be a feature of wavelets new to me :-)

you need to give fieldtrip the electrode positions: with MEG data they are usually automatically read when doing ft_preprocessing. otherwise you need to read the info (e.g. from a polhemus file) using ft_read_sens. if you don not have digitized positions, i guess that for most standard caps there are standard electrode positions in fieldtrip.

good luck,
n

On 21.03.2013, at 01:42, Ricardo Moura wrote:

> Dear all,
> I am trying to run a source localization analysis of eeg oscillatory activity. My data was recorded by a BrainAmp, and I exported using the brainvision analyzer.
> 
> Since I am very new to fieldtrip, I have a (probably very basic) doubt, and would be really glad if someone could help me.
> 
> First, when creating the leadfield, it asks for the gradiometer (cfg.grad), but I didnt figure out where I can find it. I checked the "localizing oscillatory sources using beamformer techniques" tutorial, and it seems that it can be recovered as an output of the "ft_freqanalysis" (since there is a "cfg.grad = freqPost.grad" definition), but I didnt manage to have it, even running the same parameters as in the tutorial.
> 
> Here is how I am doing the oscillatory analysis.
> cfg = [];
> cfg.method = 'wavelet';
> cfg.width = 2;
> cfg.output = 'pow';
> cfg.foi = 2:2:20;
> cfg.toi = -0.5:0.05:1;
> TFR = ft_freqanalysis(cfg, dataEEGmax);
> 
> Thanks a lot in advance,
> Best regards,
> Ricardo
> 
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