# [FieldTrip] Granger causality in time-frequency domain for source-projected MEG data

Agnese Zazio agnese.zazio at hotmail.it
Wed Dec 11 11:43:00 CET 2019

Dear Fieldtrip community,

I have a question about connectivity analysis, specifically on granger causality. I am working on MEG data at source level (LCMV method), and I am interested in studying connectivity between 2 pre-defined ROIs in 2 experimental conditions. Specifically, I would like to calculate both coherence and granger causality, keeping information on both frequency and time dimensions.
So, I run time-frequency analysis with sliding time windows of frequency-dependent length, and used this ouput for ft_connectivityanalysis (please see the code pasted below). I obtained time-frequency coherence values, and I would like to do the same for granger causality (i.e., keeping time dimension), because the effect I am interested in is narrowed in time (and so running a mtmfft may not be optimal).
I am wondering, is it possible to run granger causality in the time-frequency domain? Otherwise, how can I restrict the analysis on a time-window of interest?

Any help would be really appreciated!

Best,
Agnese

--
%time-freq analysis
cfg=[];
cfg.output='fourier';
cfg.channel=[area1 area2];
cfg.method='mtmconvol';
cfg.taper='dpss';
cfg.keeptrials='yes';
cfg.toi          = -1:0.01:1;
cfg.foi = [1:128];
cfg.tapsmofrq=0.4*cfg.foi;
cfg.t_ftimwin    = 5./cfg.foi;
tfr_A =ft_freqanalysis(cfg, data_A);
tfr_B =ft_freqanalysis(cfg, data_B);

%coherence
cfg=[];
cfg.method = 'coh';
coh_A = ft_connectivityanalysis(cfg, tfr_A);
coh_B = ft_connectivityanalysis(cfg, tfr_B);

%granger
cfg=[];
cfg.method='granger';
cfg.granger.sfmethod='bivariate';
grang_A = ft_connectivityanalysis(cfg, ?);
grang_B = ft_connectivityanalysis(cfg, ?);

--
Agnese Zazio, PhD
Cognitive Neuroscience Section,
IRCCS Centro San Giovanni di Dio Fatebenefratelli
Via Pilastroni 4, 25125 Brescia, Italy
Phone number: (+39) 0303501-596
Site: http://www.cognitiveneuroscience.it<http://www.cognitiveneuroscience.it/>
E-mail: agnese.zazio at cognitiveneuroscience.it<mailto:agnese.zazio at cognitiveneuroscience.it>

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