[FieldTrip] ft_connectivity_laggedcoherence

[Jose Herrero]

thanks Jan Mathijs for your reply, yes not to blame for not finishing up
... a lot of nice work already in his paper!

after reading your tutorial (
http://www.fieldtriptoolbox.org/project/guidelines/paper/connectivity_analysis?s[]=coherence&s[]=lags)
still would love your thoughts on this.

ideally, I'd like to find out whether a specific phase of an ultraslow
(<0.5Hz rhythmic external) signal is leading/lagging the phase of the iEEG
signal at the same frequency (effective connectivity). Would it be adequate
here to use 'granger' over 'pdc' since I'm not interested in the freq
domain (as both signals have been filtered <0.5Hz). Note that dominant
frequencies between signals differs a lot.

Also, interesting to know if there are consistent phase lags in some iEEG
electrodes but not others (functional connectivity). which ft measures
would you advice particularly if you want to compute phase lags? The Nolte
(2004) paper suggested cfg.method = 'coh' & cfg.complex = 'imag' as being a
superior method. Is that right for this particular case? Would it be
adequate here to use cfg.method='wpli'  or 'wpli_debiased' ? I've explored
other methods (Guo, 2007, PLoS) but not sure they're adequate for this
specific case (where dominant frequencies between signals differs a lot).

thanks


On Thu, May 17, 2018 at 3:26 AM, Schoffelen, J.M. (Jan Mathijs) <
jan.schoffelen at donders.ru.nl> wrote:

> Dear Jose,
> As far as I know, this code is not functional. The first author of the
> paper started the implementation in fieldtrip-style, but never finished it.
> Also, note that the method itself is not strictly speaking a
> ‘connectivity’ measure, but it was intended to identify rhythmicity within
> signals.
>
> Best wishes,
> Jan Mathijs
>
> J.M.Schoffelen, MD PhD
> Associate PI, VIDI-fellow
> Telephone: +31-24-3614793
> Physical location: room 00.028
> Donders Centre for Cognitive Neuroimaging, Nijmegen, The Netherlands
>
>
>
>
> On 16 May 2018, at 18:17, Jose Herrero <jose.herrero66 at gmail.com> wrote:
>
> dear Fieldtrippers,
>
> I'm comparing different coherence methods including the fieldtrip method
> of lagged coherence.
>
> running the code with...
> cfg.method      = 'laggedcoherence';
>
> lcoh                 = ft_connectivityanalysis(cfg, freq)
> results on...
> Error using ft_connectivityanalysis (line 375)
>
> unknown method laggedcoherence
>
> running the code with...
> lcoh = ft_connectivity_laggedcoherence(cfg, freq)
> results on:
> In an assignment  A(:) = B, the number of elements in A and B must be the
> same.
> Error in ft_connectivity_laggedcoherence (line 213)
>       lagwidth(lagindx) = cfg.lag*cyclelength*lagindx;
> as 'cfg.lag' is assigned a length equal to the length of the trial
> (1x15000, single trial).
>
> if this method works, is it possible to use it to compute lagged coherence
> between an external signal (which oscillates at a freq <0.5Hz) and the iEEG
> brain signal?
>
> thanks,
> JHerr
>
>
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-- 
Jose L Herrero, PhD
Department of Neurosurgery
Northwell University Hospital
Feinstein Institute for Medical Research
New York
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