[FieldTrip] Reference to non-existent field 'mom' in ft_connectivityanalysis

[Davide Sometti]

Dear community,

I’m trying to perform connectivity analysis (*Matlab 2018b, FieldTrip
2018-12-11*), in order to obtain the absolute part of the imaginary
coherence. Here are the steps that I’ve used in order to perform it.

*1-     **First I performed the frequency analysis, on the single condition
(not showed), and on all the conditions together*

cfg = [];

cfg.channel    = chn;

cfg.method     = 'mtmfft';

cfg.output     = 'powandcsd';

cfg.taper      = 'dpss';

cfg.keeptrials ='no';

cfg.keeptapers ='no';

cfg.tapsmofrq  = 3;

cfg.foi        = [6; 11; 16; 21; 26; 40];

data_freq_all  = ft_freqanalysis(cfg, data_reject_all);



*2-    ** I computed the beamformer filters based on the entire data*

cfg=[];

cfg.method='dics';

cfg.frequency=6;

cfg.grid=lf;

cfg.grid.pos=pos;

cfg.grid.tri=tri;

cfg.headmodel=hdm;

cfg.senstype     = 'meg';

cfg.dics.projectnoise = 'yes';

cfg.dics.lambda       = '5%';

cfg.dics.keepfilter   = 'yes';

cfg.dics.realfilter   = 'yes';

cfg.dics.keepcsd       = 'yes';

cfg.dics.keepmom       = 'yes';

cfg.dics.fixedori     = 'yes';

sourceAll = ft_sourceanalysis(cfg,data_all);



*3-     **I've then performed the source analysis on each of the four
conditions, using the precomputed filter*

cfg.grid.filter=sourceAll.avg.filter;



source_pre_incl=ft_sourceanalysis(cfg,data_pre_incl);

source_pre_excl=ft_sourceanalysis(cfg,data_pre_excl);

source_post_incl=ft_sourceanalysis(cfg,data_post_incl);

source_post_excl=ft_sourceanalysis(cfg,data_post_excl);



*4-     **Finally I’ve performed the connectivity analysis*





cfg=[];

cfg.method  ='coh';

cfg.complex = 'absimag';

source_conn = ft_connectivityanalysis(cfg, source_pre_incl);



*When I try to run the connectivity analysis I get this error, and I cannot
go further in the analysis.*



Reference to non-existent field 'mom'.



Error in univariate2bivariate (line 225)

      sizmom = size(data.mom{data.inside(1)});



Error in ft_connectivityanalysis (line 449)

        [data, powindx, hasrpt] = univariate2bivariate(data, 'mom',
'crsspctrm', dtype, 'cmb', cfg.refindx, 'keeprpt', 0);





I’ve tried different solution, changing output for the frequency analysis
and method for the beamforming, like follow:



'fourier' - 'pcc'

'powandcsd' - 'pcc'

'fourier' - 'dics'

The combination fourier and pcc was the only one that worked, among the 4,
the others always gave me the same error, as above. I’m wondering why even
if I’ve specified cfg.keepmom=’yes’, this one is not present in the
structure after the source analysis.

Anyone that could help me?
Davide S.
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https://doi.org/10.1371/journal.pcbi.1002202