[FieldTrip] Questions on Functional Connectivity results using debiased wPLI

[SERGIO OSORIO GALEANO]

Yes, you made a mistake in the (assumptions underlying) the implementation:
the cfg.toi that you supply before ft_freqanalysis is not going to have any
effect if you use ‘mtmfft’ as a method, since this method just provides a
single estimate of the spectrum using the whole ’trial’ for the estimation.


Oh, that makes perfect sense. Cheers Jan! Really appreciate it.

*Sergio.*



El mié, 15 sept 2021 a las 14:29, Schoffelen, J.M. (Jan Mathijs) via
fieldtrip (<fieldtrip at science.ru.nl>) escribió:

> Hi Sergio,
> >
> > 1) Regardless of whether I use my full time window of interest (0-1.5 s)
> or whether I estimate wPLI for two separate shorter time windows (0-.7 s
> and .7-1.5 s), the results are always identical to one another. Is this
> normal behaviour in wPLI analyses or is there something potentially wrong
> with how I've implemented it?
>
> Yes, you made a mistake in the (assumptions underlying) the
> implementation: the cfg.toi that you supply before ft_freqanalysis is not
> going to have any effect if you use ‘mtmfft’ as a method, since this method
> just provides a single estimate of the spectrum using the whole ’trial’ for
> the estimation.
>
> > 2) I notice that wPLI values are way lower for low-frequencies (4-7hz)
> than for higher-frequencies (8-12hz and 15-30hz). While this could be a
> real effect associated with my task, the fact that this result is
> consistent across different conditions makes me wonder whether I've done
> something wrong in the ft_freqanalysis configuration.
>
> I think that this is just a property of the data.
>
> Best wishes,
> Jan-Mathijs
>
>
> >
> > Thanks a lot in advance for any help anyone can provide!
> >
> > -----------
> >
> > cfg                 = [ ];
> > data               = ft_preprocessing(cfg,rwdata);
> >
> > %resample data
> > cfg                      = [ ];
> > cfg.resamplefs   = 250;
> > data                    = ft_resampledata(cfg, data);
> >
> > data =
> >   struct with fields:
> >
> >       fsample: 250
> >       trial:   {1×117 cell}
> >       time:  {1×117 cell}
> >       label: {100×1 cell}
> >       cfg:    [1×1 struct]
> >
> > % next, call the ft_freqanalysis function in our source data
> > cfg                     = [ ];
> > cfg.output          = 'fourier';
> > cfg.method        = 'mtmfft';
> > cfg.taper            = 'dpss';
> > cfg.foi                 = linspace(4,30,30);
> > cfg.tapsmofrq     = 4;
> > cfg.toi                 = 0:.02:1.5;   % try 0:.02:.7 and .7:.02:1.5
> > tf_data                = ft_freqanalysis(cfg,data);
> >
> > tf_data =
> >   struct with fields:
> >
> >             label:     {100×1 cell}
> >             dimord: 'rpttap_chan_freq'
> >             freq:       [1×30 double]
> >             fourierspctrm: [4563×100×30 double]
> >             cumsumcnt: [117×1 double]
> >             cumtapcnt:   [117×1 double]
> >             cfg:               [1×1 struct]
> >
> > % estimate wPLI values
> > cfg                    = [ ];
> > cfg.method       = 'wpli_debiased';
> > connect_data   = ft_connectivityanalysis(cfg,tf_data);
> >
> > connect_data =
> >   struct with fields:
> >
> >                label:     {100×1 cell}
> >                dimord:  'chan_chan_freq'
> >                wpli_debiasedspctrm: [100×100×30 double]
> >                freq:  [1×30 double]
> >                cfg:   [1×1 struct]
> >
> > Best,
> >
> > Sergio.
> >
> > _______________________________________________
> > fieldtrip mailing list
> > https://mailman.science.ru.nl/mailman/listinfo/fieldtrip
> >
> https://urldefense.com/v3/__https://doi.org/10.1371/journal.pcbi.1002202__;!!HJOPV4FYYWzcc1jazlU!v6GcyYsHF6VUmzXm8BB3M6rFfwWnSYCxD7hg5IzSXjBU2SvnlyfRyykO5BhpyzahCLvCtBzdjU2HPc4$
>
>
> _______________________________________________
> fieldtrip mailing list
> https://mailman.science.ru.nl/mailman/listinfo/fieldtrip
> https://doi.org/10.1371/journal.pcbi.1002202
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.science.ru.nl/pipermail/fieldtrip/attachments/20210915/b038fa6b/attachment.htm>