[FieldTrip] Interpretation of Granger spectrum and link with directed coherence

[Schoffelen, J.M. (Jan Mathijs)]

Hi Simon,

You may want to check the ‘connectivity’ section in the following link:

http://www.fieldtriptoolbox.org/references_to_implemented_methods

It contains links to papers that might be relevant for you. I’d start from the first one, sorry for the shameless self-promotion.

Best,
Jan-Mathijs


> On 19 May 2017, at 13:51, Simon Van Eyndhoven <Simon.VanEyndhoven at esat.kuleuven.be> wrote:
> 
> Dear FieldTrip community,
> 
> As a novice in EEG connectivity analysis, I am trying to reproduce and understand the connectivity tutorial of the website (http://www.fieldtriptoolbox.org/tutorial/connectivity).
> 
> I was hoping that someone could shed light on the computation of the Granger frequency spectrum:
> 
> cfg           = [];
> cfg.method    = 'granger';
> granger       = ft_connectivityanalysis(cfg, mfreq);
> 
> More specifically, I would like to know which computations are done to obtain the values in granger.grangerspctrm. (Unfortunately, inspecting the paper by Brovelli et al. PNAS (2004), as indicated in ft_connectivity_granger did not clear this up...)
> 
> Moreover, I wonder what the relationship is between the Granger spectrum and other metrics such as (partial) directed coherence (DC / PDC) and directed transfer function (DTF), which also provide connectivity information in the form channels x channels x frequencies?
> 
> In the appendix in Van Mierlo et al., "Functional brain connectivity from EEG in epilepsy: Seizure prediction and epileptogenic focus localization" and in Baccala and Sameshima, "Partial directed coherence: a new concept in neural structure determination", it is explained that both DC and DTF are computed using the transfer function matrix H(f), while PDC is computed using the A(f) matrix. Is this the reason why only PDC is termed 'partial', and the others not (even though they are also computed in a multivariate framework, i.e. taking all available variables into account)?
> 
> Although I could not find an answer to my questions in the mailing archives, I apologize if this question has been asked before.
> 
> Thank you in advance for your help!
> Best regards,
> 
> Simon
> 
> 
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