[FieldTrip] Time-Frequency Plot Granger Causality
luckyluke1979 at yahoo.com.ar
Thu Dec 12 09:19:46 CET 2013
Following the tutorial on connectivity analysis I am trying to implement Granger Causality on simulated signals. I can reproduce all the results that appear in the tutorial in my dataset but I cannot obtain a graph of Wavelet-based granger causality with the format:
-x axis: time
-y axis: frequency
This graph should allow me to compare in a single figure how channel 1 granger causes channel 2 at a range of frequencies as a function of time (like in Fig 3 of Dhamala et al, 2008).
My problem is that I cannot figure out how to produce this graph with the tutorial functions as they seem to automatically compute Granger Spectra for the whole epoch. In the tutorial demo the structure 'freq' has dimord: 'rpttap_chan_freq', and the structure 'granger' has dimord: 'chan_chan_freq'. What I am looking for is a function that returns a structure with the granger spectra computed with dimord of 'chan_chan_freq_time'
1- I've tried running 'freq = ft_freqanalysis(cfg, data);' and then '[output] = ft_connectivity_csd2transfer(freq);' with all types of parameters but I could not reach to a solution. Is there a way of building a time-frequency granger spectra within fieldtrip?
2- Alternatively to 1, I thought that I could compute non-parametric Granger Spectra for different time windows inside each epoch and then concatenate the results. Before doing this I would like to be sure that I am not missing a way of doing it that it's already implemented in fieldtrip (I have just started using Fieldtrip a short time ago)
Thanks a lot
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