[FieldTrip] Questions about coherence statistics on source level data

[Q Meng]

Dear list,

My apology, it should be a comparison of coherence value between 2
conditions in a within subject design.

In addition to my previous question on how to implement a non-parametric
permutation test on the difference of coherence values, I would like to
consult that in case I used hanning window as a single taper, what should I
do with the Z spectra equation described in Jan-Mathijs's J.Neurosci. 2011
paper? As it will result in infinite values, right?

Best,
Qing Meng

On Tue, Aug 1, 2017 at 4:42 PM, Q Meng <q.meng301 at gmail.com> wrote:

> Dear list,
>
> I'm running source analysis using DICS on my MEG data following the
> cortical-muscular coherence tutorial and now would like to compare the
> source level coherence value between 2 conditions in a between subject
> design.
>
> I found some older posts on this topic from the discuss list (
> https://mailman.science.ru.nl/pipermail/fieldtrip/2011-
> September/004279.html)  (https://mailman.science.ru.
> nl/pipermail/fieldtrip/2016-March/010166.html). Following the
> instructions, I Z-transformed the coherence manually and specified
> cfg.statistic = 'ft_statfun_diff' and then did the cluster based
> non-parametric permutation test. However, I got an error message says *"Error
> using ft_statistics_montecarlo (line 242) could not determine the
> parametric critical value for clustering"* right after the statistical
> analysis started. Please see below a snippet of code:
>
> ...
> Z- transform coherence manually and creating 0-coherence data
> ...
>
> cfg                     = [];
> cfg.method        = 'montecarlo';
> % cfg.statistic           = 'ft_statfun_depsamplesT';
> cfg.statistic        = 'ft_statfun_diff';
> cfg.parameter    = 'coh';
> cfg.correctm      = 'cluster';
> cfg.numrandomization    = 1000;
> cfg.alpha               = 0.05;
> cfg.clusteralpha        = 0.05;
> cfg.tail                = 0;
> cfg.clustertail         = 0;
> cfg.correcttail         = 'alpha';
> cfg.connectivity        = VertConn;
>
> nsubj                   = 19;
> cfg.design(1,:)         = [1:nsubj 1:nsubj];
> cfg.design(2,:)         = [ones(1,nsubj) ones(1,nsubj)*2];
> cfg.uvar                = 1; % row of design matrix that contains unit
> variable (in this case: subjects)
> cfg.ivar                = 2; % row of design matrix that contains
> independent variable (the conditions)
>
>
> stat = ft_sourcestatistics(cfg, data_meg_source_cohe_sentence_dics_parsing_B2_ICA{:},
> data_meg_source_cohe_sentence_dics_parsing_B5_ICA{:});
>
>
> Before this, I just used  cfg.statistic = 'ft_statfun_depsamplesT' to
> compare the coherence value between two conditions and the program itself
> worked well.
>
> Does anyone have an idea where my problem could be or what I should do instead?3
>
> Thanks for your help!
>
> Best,
>
> Qing
>
>
>
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