[FieldTrip] cluster-based permutation test on WPLI

Cristiano Micheli michelic72 at gmail.com
Sat May 16 16:17:25 CEST 2015

Dear Zsolt
I experienced difficulties and encountered many pitfalls along the way too.
What exactly will your metric be? wPLI of post onset versus baseline
difference/ratio? wPLI difference of the two conditions? Do you common
average re-reference your data before?
The statistics that you will use will depend on your design. I would
personally try a non-parametric design where you shuffle the index of the
trials of one condition (if you do wPLI1-wPLI2) and consider the proportion
of iterations exceeding the measured wPLI difference. Please consider
though that both conditions should have the same number of trials.

Could you attach the programming attempts that you tried so far together
with the exact error outputs?

I hope this helps so far.
Cris Micheli

On Wed, May 13, 2015 at 5:28 PM, Zsolt Turi <zsoltturi at gmail.com> wrote:

> Dear all,
> I would like to perform a cluster-based permutation test on weighted phase
> lag index values by using a within-subjects experimental design. I have two
> conditions (congruent and incongruent one) and my goal is to compute WPLI
> between certain channel combinations (FCz and F3 for instance) and see the
> WPLI change let’s say in 3-9 Hz and -100 to 500 ms between the two
> conditions.
> I experienced some difficulties after the point when I calculated the
> WPLI data for each participant. To perform the above-mentioned comparison,
> shall I use ‘ft_freqstatistics’for the cluster-based permutation test?
> If I am right, which command shall I use to organize individual WPLI data,
> in order to create a correct input for ‘ft_freqstatistics’. According to
> the tutorial, in case of time-frequency data it is ft_freqgrandaverage.
> However, if I use it for WPLI data, I have the following error: “This
> function requires freq data as input”.
> Could you please recommend me a tutorial, reference documentation or some
> comment on this issue?
> Thanks for any suggestions in advanced and let me know if the description
>  of my problem is not clear!
> Zsolt
> --
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> Department of Clinical Neurophysiology
> Georg-August University, Göttingen
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