[FieldTrip] ft_prepare_leadfield: no electrodes or gradiometers specified

[Stephen Politzer-Ahles]

Kevin,

I'm not familiar with ft_prepare_leadfield, but in the past when I had
similar electrode-related error messages I was able to resolve it by first
running

elec = ft_read_sens(filename, ...)

and then adding elec to the data structure. I believe the file I used for
ft_read_sens was a layout file I exported from EEGLAB.

Best,
Steve Politzer-Ahles

Message: 3
> Date: Tue, 04 Oct 2011 14:51:29 +0200
> From: Kevin Lam <K.Lam at donders.ru.nl>
> To: fieldtrip at donders.ru.nl
> Subject: [FieldTrip] ft_prepare_leadfield: no electrodes or
>        gradiometers    specified
> Message-ID: <4E8B0151.4060109 at donders.ru.nl>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hi all,
>
> I recorded EEG using BrainVision Recorder and have analyzed the data
> (ERP and TFR). Now, I would like to determine the source of the TFR
> effects. (I've been following, more or less, this procedure:
> http://fieldtrip.fcdonders.nl/tutorial/beamformer)
>
> I'm having trouble executing ft_prepare_leadfield. Here's what I've done
> in the preceding steps, per participant:
>  - ft_redefinetrial to specify the time of interest for each of the two
> conditions
>  - ft_freqanalysis to calculate CSD matrix per the freq of interest for
> each condition
>  - ft_volumesegment using 'spm' for coordsys
>  - ft_prepare_headmodel using 'singlesphere' for method
>
> Now, when I attempt ft_prepare_leadfield, I get an error saying 'no
> electrodes or gradiometers specified'. I understand what the function
> needs, but I don't have the input file it's asking for. It's not the
> .lay file - I gave this a try.
>
> Please advise. Thanks in advance!
>
> Regards,
> Kevin
>
>
> ------------------------------
>
> Message: 4
> Date: Tue, 4 Oct 2011 15:05:10 +0200
> From: Davide Rivolta <drivolta81 at gmail.com>
> To: Email discussion list for the FieldTrip project
>        <fieldtrip at donders.ru.nl>
> Subject: [FieldTrip] power line filter
> Message-ID:
>        <CAMkcSw7oubKNktYkJz8_V3ObcP=zbEruxRn3YLA2yBkCRhgFRg at mail.gmail.com
> >
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear all,
>
> I am trying to get rid of the power line noise. I use the dftfilter as
> indicated on the website.
>
> This works very well for most of the subjects. However, for some of them, I
> still get the noise.
>
> My trials have a different lenght: between 500 ms until 3 seconds.
>
> This is the script I used.
>
>
>  filterfreqs = [49:1:51 99:1:101 149:1:151];
>
>    cfg.dftfilter      =  'yes';
>    cfg.dftfreq      = filterfreqs;
>    cfg.padding    = 10;
>
>    dataprepro_syn = ft_preprocessing(cfg);
>
>
> The pad of 10 is the same as another already published study that used the
> same task.
>
>
> Attached is a picture of the problem (blu is baseline, red is stimulus).
> This is the result of multitepering (dpss).
>
>
> Thanks for your help,
>
> Davide
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> End of fieldtrip Digest, Vol 11, Issue 3
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>



-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://www.linguistics.ku.edu/
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