[FieldTrip] Resting State EEG Connectivity

[Elene Beitia Loinaz]

Dear all,

Continuing with the connectivity issue, we have seen that the problem of
memory come from the size of the leadfield`s grid used previously for
source reconstruction and now for connectivity. The variable related with
that grid is *data.pos,  *which was created in* ft_prepareleadfield*. This
value contains the coordinates of the centroids' voxels, related with the
grid. As this variable is too large, it supposes really high computational
effort that matlab cannot handle.

We want to cluster the *data.pos* voxels coordinates into different brain
regions such as: temporal area, frontal field....

Does anyone know how we can group those coordinates into regions in order
to decrease the size of *data.pos* variable needed in
*ft_connectivityanalysis* function?

Thank you in advanced.

Hau idatzi du Elene Beitia Loinaz (elene.beitia at alumni.mondragon.edu)
erabiltzaileak (2019 mai. 7, ar. (11:11)):

> Hi Fieldtripers,
>
> We are trying to perform a conectivity analysis using source reconstructed
> data. We have seen that *ft_connectivityanalysis *can be calculated using
> the output of *ft_freqanalysis *or *ft_sourceanalysis. *Someone knows
> which are the benefits of using the results obtain in *ft_sourceanalysis *to
> perform the connectivity analysis?
>
> Furthemore, we have problems when we compute the choerence approach with
> the source reconstructed data.
>
> *Our code:*
>
> cfg           = [];
> cfg.method    = 'coh'
> coh           = ft_connectivityanalysis(cfg, beamformer);
>
> *The error that we obtain is:*
> Out of memory. Type "help memory" for your options.
>
> Error in univariate2bivariate (line 314)
>          data.crsspctrm = (transpose(mom)*conj(mom))./nrpt;
>
> Error in ft_connectivityanalysis (line 449)
> [data, powindx, hasrpt] = univariate2bivariate(data, 'mom', 'crsspctrm',
> dtype, 'cmb', cfg.refindx,'keeprpt', 0);
>
> This segment of code has been concluded following the tutorials below:
> http://www.fieldtriptoolbox.org/tutorial/networkanalysis/
> http://www.fieldtriptoolbox.org/tutorial/connectivity/
>
> http://www.fieldtriptoolbox.org/workshop/meg-uk-2015/fieldtrip-connectivity-demo/
>
> Thank you in advanced,
>
> Waiting for your answer.
>
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https://doi.org/10.1371/journal.pcbi.1002202