[FieldTrip] Using fieldtrip statistic for cluster analysis of an already existing dataset

[Stephen Politzer-Ahles]

Caroline,

This should be possible (I recently did something very similar, although I
was analysizing ERPs rather than ERSPs).

First you need to export the data for each subject from EEGLAB to Fieldtrip
using EEGLAB's function eeg2fieldtrip(); when I did this I specified the
option 'timelockanalysis' to compute ERPs of the EEGLAB data, but in  your
case I guess you will want to use 'freqanalysis' instead.

Then, you need to compute grand averages using ft_freqgrandaverage() with
cfg.keepindividual='yes'. Then you will be ready to perform cluster
statistics following the instructions at
http://fieldtrip.fcdonders.nl/tutorial/cluster_permutation_freq .

Best,
Steve Politzer-Ahles


Message: 1
> Date: Wed, 28 Sep 2011 10:46:16 +0200
> From: "Lustenberger Caroline" <Caroline.Lustenberger at kispi.uzh.ch>
> To: <fieldtrip at donders.ru.nl>
> Subject: [FieldTrip] Using fieldtrip statistic for cluster analysis of
>        an      already existing dataset
> Message-ID: <8D58B6880DD231469FA0128331363CED03DB01AB at exzh1.kispi.int>
> Content-Type: text/plain; charset="us-ascii"
>
> Dear all
>
> Using EEGlab I have calculated ITC and ERSP of 16 subjects of 1 channel
> and the frequency range 1-4Hz (in average), thus I have 2 data arrays:
>
> 1st Condition Sham: 16 x 185 --> 16=number of subjects, 185=timepoints
> with event-related spectral values or intertrial coherence values
> 2nd Condition Field: 16 x 185
>
> To see if there is any difference between the 2 conditions in all
> timepoints I performed 185 paired t-tests and now I should control for
> multiple comparison using a cluster analysis (meaning find out the
> probability that a certain number of neighbour-timepoints are
> suprathreshold).
>
> Is there a possibility to do that using fieldtrip statistics? And how
> can I do that?
>
> Thank you very much for your help
> Caroline
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-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://www.linguistics.ku.edu/
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