clusteranalysis inter-trial phase-locking

[Eric Maris]

Hi Stephan,



> I would like to use clusterrandanalysis to test significant differences of
> inter-trial phase-locking values between conditions, within subjects.
> I think clusterrandanalysis, with the 'indepsamplesZcoh' configuration
needs
> cross- and autospectra as input, to test between channel coherence
differenes.
> I was wondering if there is a way to use this function to compute
> inter-trial phase locking differences.

I guess you want to compare the PLF/coherence values between experimental
conditions. (PLF/coherence itself is calculated OVER trials, as correctly
show in your code snippet below.)


> PS: I compute phase-locking with output='Fourier' and keeptrials='yes', in
> freqanalysis. then:
> frq.plv = squeeze(abs(mean(frq.fourierspctrm./abs(frq.fourierspctrm),1)));
> I hope this is ok?

Yes, this is OK. However, you can improve by using spectral smoothing,
preferably using multitapers. When you have a small number of very long
trials this will make a big difference. Have a look in our paper (Maris,
Schoffelen, Fries, 2007) in the Journal of Neuroscience Methods.

>
> would it be legitimate to change clusteranalysis to accept fouriersptrm as
> input and introduce the phase-locking calculation step for every random
> partition? then compute the z-statistics in clusterstatistics with those
values?

I will not change clusterrandanalysis to accept fourierspctrm data. However,
I may change freqstatistics (one of the successors of clusterrandanalysis)
to accept fourierspctrm data (and supporting multitapers). This could be in
the form of a small collaborative project. You can find me at
maris at nici.ru.nl.


Greetings,

Eric Maris




>
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----------------------------------
The aim of this list is to facilitate the discussion between users of the FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/fcdonders/fieldtrip.