[FieldTrip] Read only EEG data from combined MEG/EEG ctf file

Tobias Trame tobiastrame at uni-muenster.de
Fri Sep 12 18:23:17 CEST 2014

Hi everybody!

I'm trying to read only the EEG data from a combined MEG/EEG ctf file in order
to create leadfields later on, but the function "ft_read_sens" just returns
the gradiometer information in a 'grad' field. It searches for an 'elec'-field
in the header of the data which is not present. Is there a configuration to
get the EEG-elecrodes by using "ft_read_sens"?

My first attempt was to write the EEG-Information from the header by hand
using the following code:

hdr = ft_read_header('subject.ds', 'headerformat', 'ctf_ds');
elec.elecpos = [hdr.orig.eeg.pos]';
elec.chanpos = [hdr.orig.eeg.pos]';
elec.label = {hdr.orig.eeg.name}';
elec.type = 'eeg';
elec.unit = 'cm';

But now I get a similar problem if I want to create leadfields from timelock
data. After doing the timelock analysis using

timelock_data = ft_timelockanalysis(cfg, mydata);

the structure timelock_data contains just a 'grad' and no 'elec' field so that
ft_prepare_leadfield(cfg, timelock_data) always ignores the EEG-elecrodes and
tries to use the gradiometes - even if I put the electrodes defined above into

Thanks for any suggestions!


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