[FieldTrip] extracting individual trial phase connectivity

[Hwee Ling Lee]

Dear Roey, Julian and Tobias,

Thanks for the feedback.

Given your suggestions, I now intend to try to calculate the deviation of
single trials from the mean phase difference (PLV). Pardon my ignorance,
however, I still experience some problems with calculating plv for single
trials.

Using this code to extract PLV:

    cfg                 = [];
    cfg.trials          = 'all';
    cfg.keeptrials      = 'yes';
    cfg.channel         = {'all'};
    cfg.removemean      = 'yes';
    cfg.method           = 'plv';
    cfg.channelcmb       = {cfg.channel, cfg.channel};
    HLF_pre_c200plv      = ft_connectivityanalysis(cfg, HLF_pre_c200);

Although I've specified to keep individual trials, ft_connectivityanalysis
still show averaged PLV across trials for the output. Could anyone of you,
or someone else, kindly highlight my mistake in my calculation?

Thank you very much!

Best wishes,
Hweeling



On 18 September 2014 16:39, Tobias Staudigl <tobias.staudigl at uni-konstanz.de
> wrote:

>  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>
> 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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>> fieldtrip at donders.ru.nl
>> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>>
>
>
>
> _______________________________________________
> fieldtrip mailing listfieldtrip at donders.ru.nlhttp://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>
>
>
> --
> Dr. Tobias Staudigl
> Fachbereich Psychologie - ZPR
> Postfach ZPR
> 78457 Konstanz
> ZPR, Haus 12
> Tel.: +49 (0)7531 / 88 - 5703
>
>
> _______________________________________________
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> fieldtrip at donders.ru.nl
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>



-- 
=================================================
Dr. rer. nat. Lee, Hwee Ling
Postdoc
German Center for Neurodegenerative Diseases (DZNE) Bonn

Email 1: hwee-ling.lee<at>dzne.de
Email 2: hweeling.lee<at>gmail.com

https://sites.google.com/site/hweelinglee/home

Correspondence Address:
Ernst-Robert-Curtius Strasse 12, 53117, Bonn, Germany
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