[FieldTrip] granger causality on beamformer data

[Julian Keil]

Hi Tyler,

I can't comment on the usefulness of directionality between 1400 sources,
but keep in mind, that you would have to compute something in the range of
1400*1400
connections, so I hope you have a fast computer.

As for the regions, in case you want to use anatomically defined regions,
you an either use the atlases (atlanti? atlae?) that come with fieldtrip or
generate a mask from this website:
http://neuro.imm.dtu.dk/services/jerne/ninf/voi.html

The general idea is to build a grid with a gridpoint per voxel of your MRI
using ft_prepare_sourcemodel. Then you can check which of your virtual
channels is closest to the voxel-gridpoints and thus select the virtual
channels that are inside your ROI.

In the first case, you can use ft_volumelookup to find the voxels
corresponding to your ROI. In the latter case you can just use the mask and
check which voxels are 1 (= inside your ROI).

I hope that helps, if you have specific questions, feel free to ask.

Best,

Julian


On Tue, May 27, 2014 at 7:44 AM, Tyler Grummett <
tyler.grummett at flinders.edu.au> wrote:

>  ​Hello fieldtrippers,
>
>
>  I was just wondering whether it would be sensible to do granger
> causality on all 1400 virtual channels, as calculated using beamformer.
>
>
>  Or should you do a PCA reduction of some description beforehand.
>
>
>  I was also wondering how to create regions of interest. Some of my
> colleagues think that we should use some kind of spatial ICA technique.
>
>
>  Im open to all suggestions.
>
>
>  Tyler
>
>
>    *************************
>
>  *Tyler Grummett ( BBSc, BSc(Hons I))*
> *PhD Candidate*
> *Brain Signals Laboratory*
> *Flinders University*
> *Rm 5A301*
> *Ext 66124*
>
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