Partial Directed Coherence

[jan-mathijs schoffelen]

Dear Ivana,

There is not so much information on the fieldtrip wiki as of yet. But
I am working on it.
For the time being, perhaps you know that in order to compute partial
directed coherence, you need to first fit an autoregressive model to
your time domain data. This is necessary to obtain a thing which is
known as the spectral transfer function, from which PDC will be derived.
Therefore you need to do two things before you can call
ft_connectivityanalysis:

use ft_mvaranalysis to obtain the MVAR-model of your data.
use ft_freqanalysis (cfg.method = 'mvar') to obtain the spectral
transfer function.

Note that you do not need to specify partchannel when you will be
computing pdc; the idea is that by fitting a multivariate model to all
channels of interest, the 'partialisation' is achieved. At least
that's the theory...

I hope to find time to work on the documentation soon.

Best wishes,

Jan-Mathijs


On Nov 9, 2010, at 11:36 AM, Ivana Konvalinka wrote:

> Hello,
>
> I was wondering if it would be possible to get more information on
> partial directed coherence, using ft_connectivityanalysis. I've been
> trying to set it up on the frequency data of pairs of EEG
> electrodes, by partialling out motor evoked fields.
>
> Hence, something like this:
> cfg.method = 'pdc';
> cfg.channelcmb = { pairs of electrodes here };
> cfg.partchannel = { electrodes containing fourier spectra of motor
> events };
>
> pdc1 = ft_connectivityanalysis(cfg, freqs);
>
> I get the following error: "reference to non-existent field
> 'transfer'".
>
> Is there any more documentation on this method in fieldtrip?
>
> Thanks in advance!
>
> Ivana
>
>
> --
> Ivana Konvalinka
> PhD Student
> Interacting Minds Group
> Center of Functionally Integrative Neuroscience
> University of Aarhus
> Denmark
>
> http://www.interacting-minds.net
> http://www.cfin.au.dk
>
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Dr. J.M. (Jan-Mathijs) Schoffelen
Donders Institute for Brain, Cognition and Behaviour,
Centre for Cognitive Neuroimaging,
Radboud University Nijmegen, The Netherlands
J.Schoffelen at donders.ru.nl
Telephone: 0031-24-3614793


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