[FieldTrip] Circular Correlation coefficient

[Julian Keil]

Dear David,

I won't discuss whether this is a sensible comment by the reviewer, but here are some basic steps that you could take.

To compute the circular correlation between two signals, you obviously need to obtain the phase angles first.
One option to do this is to use a Hilbert transform on band-pass filtered data (on a single-trial level)
As soon as you have your single trial phase angles, you can compute the correlation between two signals within each subject.
Once you have done this, you could see whether there is a consistent pattern over subjects.

You can find similar approaches in the following papers:

van Elswijk, G., Maij, F., Schoffelen, J.-M., Overeem, S., Stegeman, D. F., & Fries, P. (2010). Corticospinal Beta-Band Synchronization Entails Rhythmic Gain Modulation. Journal of Neuroscience, 30(12), 4481–4488. http://doi.org/10.1523/JNEUROSCI.2794-09.2010

Keil, J., Timm, J., SanMiguel, I., Schulz, H., Obleser, J., & Schonwiesner, M. (2014). Cortical brain states and corticospinal synchronization influence TMS-evoked motor potentials. Journal of Neurophysiology, 111(3), 513–519. http://doi.org/10.1152/jn.00387.2013

Good luck,

Julian

Am 02.02.2016 um 09:14 schrieb David Syloni:

> Dear Julian,
> 
> Thank you for the answer. I was asked by reviewers to calculate  circular correlation instead of PLV.  Sorry for too general description.
> Actually, I found  the toolbox , but I don't understand how to compute " sample of angles in radians" (the input for the circ_corrcc function ).
> I would very appreciate a help to transform my fieldtrip data to the input format , required by circ_corrcc.
> 
> Thanks!
> 
> 
> David
> 
> On Tue, Feb 2, 2016 at 9:57 AM, Julian Keil <julian.keil at gmail.com> wrote:
> Hi David,
> 
> to compute circular statistics (e.g. phase correlations) you need to leave fieldtrip a bit.
> Here's the toolbox I usually use: http://www.mathworks.com/matlabcentral/fileexchange/10676-circular-statistics-toolbox--directional-statistics-
> 
> As you don't describe why you need circular statistics, it's a bit hard to give a more helpful answer.
> 
> Good luck,
> 
> Julian
> 
> Am 01.02.2016 um 13:40 schrieb David Syloni:
> 
> > Dear Fieldtripers,
> >
> > I'm trying to apply connectivity analysis with  continuous EEG data.
> >
> > I'm using:
> >
> >
> >
> > cfg           = [];
> > cfg.method    = 'mtmfft';
> > cfg.taper     = 'dpss';
> > cfg.output    = 'fourier';
> > cfg.tapsmofrq = 4;
> > cfg.width=2;
> > cfg.foilim     = [0 250];
> > cfg.keeptrials = 'yes';
> > freq          = ft_freqanalysis(cfg, data_no_artifacts);
> >
> >
> >
> >
> > cfg           = [];
> > cfg.method    = 'plv';
> > 'mtmfft'
> > cfg.foilim     = [8 12];
> > cfg.bandwidth=5;
> > cfg.tapsmofrq  = 4;
> > cfg.keeptrials = 'yes';
> > cfg.output    = 'powandcsd';
> > cfg.channelcmb       = c;
> > coh           = ft_connectivityanalysis(cfg, freq);
> >
> > Right now I should calculate Circular Correlation  and I'm stuck with it.
> >
> > I would very appreciate your help!
> >
> > Thanks in advance,
> >
> > David
> > _______________________________________________
> > fieldtrip mailing list
> > fieldtrip at donders.ru.nl
> > http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
> 
> 
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