[FieldTrip] extracting individual trial phase connectivity

[Tobias Staudigl]

Dear Hweeling,

I agree with Roey that coherence/PLV cannot be calculated for individual 
trials.
However, you could try to use the deviation (in each single trial) from 
the mean phase as an approximation.

Good luck!
Tobias



Am 18.09.2014 15:32, schrieb Roey Schurr:
> Dear Hweeling,
>
> Unfortunately I am not yet familiar with the PPC measure, but I guess 
> that being a pairwise phase *consistancy* measure, it is defined over 
> a set of trials, and can not be calculated for any individual trial 
> (like coherence, or PLV)?
>
> Just quickly reading through "The pairwise phase consistency: A 
> bias-free measure of rhythmic neuronal synchronization" (Vinck et al., 
> 2010), this seems to be the case.
>
> Hope this helps,
> roey
>
> On Thu, Sep 18, 2014 at 3:30 PM, Hwee Ling Lee <hweeling.lee at gmail.com 
> <mailto:hweeling.lee at gmail.com>> wrote:
>
>     Dear all,
>
>     I've got a question regarding extracting pairwise phase
>     consistency of individual trials for each subject.
>
>     Using the connectivity analyses tutorial as a reference, I
>     extracted the PPC using the fourier information from the mtmfft
>     (dpss taper).
>
>     Here's an example of my code:
>
>         cfg                 = [];
>         cfg.output          = 'fourier';
>         cfg.channel         = {'all'};
>         cfg.method          = 'mtmfft';
>         cfg.keeptrials      = 'yes';
>         cfg.tapsmofrq       = 5;
>         % find the index for the c200 condition
>         pre_c200_idx = find(data8.trialinfo == 200);
>         cfg.trials          = pre_c200_idx;
>         cfg.foilim          = [0 100]; % either the full range of
>     frequencies (data2.hdr.Fs/2) or up to 100 Hz
>         cfg.taper           = 'dpss';
>         HLF_pre_c200        = ft_freqanalysis(cfg, data8);
>
>     The PPC is extracted using this code:
>
>         cfg                 = [];
>         cfg.trials          = 'all';
>         cfg.keeptrials      = 'yes';
>         cfg.channel         = {'all'};
>         cfg.removemean      = 'yes';
>         cfg.method           = 'wppc';
>         cfg.channelcmb       = {cfg.channel, cfg.channel};
>         HLF_pre_c200wppc      = ft_connectivityanalysis(cfg,
>     HLF_pre_c200);
>
>     Although I've specified to keep individual trials, my output is
>     still a 'chan_freq' dimord variable. It does not contain any
>     individual trial PPC information. Is there a way to extract the
>     connectivity for individual trials?
>
>     Thanks.
>
>     Cheers,
>     Hweeling
>
>
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>
>
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-- 
Dr. Tobias Staudigl
Fachbereich Psychologie - ZPR
Postfach ZPR
78457 Konstanz
ZPR, Haus 12
Tel.: +49 (0)7531 / 88 - 5703

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