[FieldTrip] extracting individual trial phase connectivity

[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>
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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