[FieldTrip] Importing '.mat' data in to fieldtrip

"Jörn M. Horschig" jm.horschig at donders.ru.nl
Wed Jul 11 10:30:58 CEST 2012

Dear Roshan,

0) Welcome to FieldTrip ;)

1) FieldTrip usuaully reads in the stimulus channel and refers to the 
triggers as events. See also here:
trialinfo can be used for that when you have segmented trials. Actually, 
there is no obligation how trialinfo should look like, you can put 
whatever information in that you want. I got stimulus trigger, stimulus 
offset sample, response sample, response trigger and some additional 
flags in there, so everything that facilitates in sorting trials 
according to some criteria.
To find out what data you have, you can try to use ft_senstype

2) you might want to look at the Donders Machine Learning Toolbox, which 
is under external/dmlt. For the design, I assume it's an ordinary design 
matrix, so maybe you want to read the walkthrough and these tutorials:

Good luck with the data and have fun with FieldTrip.


On 7/11/2012 5:25 AM, Roshan Nair wrote:
> Hi,
> I have MEG/EEG data in '.mat' format(Biomag 2012 data analysis dataset).
> The data is already epoched. It was straightforward to convert it in to the
> required fieldtrip structure - {label, fsample, trial, time} and run
> ft_databrowser on it. No problems so far.
> However, I feel I might be going wrong with the following:-
> 1. The trials include data for STI(stimulus) channels(I believe its an
> Elekta Neuromag Vectorview 306 system)? Is there a 'fieldtrip' way to
> represent this. Is this what 'data.trialinfo' is for? If so, how should I
> populate the trialinfo field.
> 2. The dataset comes with a file called 'design' with one entry(an
> integer) per trial. This is the category of the
> stimulus(living/non-living)presented to the subject for each trial. This is
> the output my classifier will be trained on. I'm assuming fieldtrip has
> some standard way of including this. I noticed, the multivariate analysis
> mentions a parameter called 'design'.
> Sorry, if thats confusing, but, I'm new to fieldtrip and MEG data.
> Thanks!
> Roshan
> _______________________________________________
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> fieldtrip at donders.ru.nl
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Jörn M. Horschig
PhD Student
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognitive Neuroimaging
Radboud University Nijmegen
Neuronal Oscillations Group

P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands

E-Mail: jm.horschig at donders.ru.nl
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