About average_orientations.txt

[nana-zhang]

Hello, in the output/connectivity.a2009s file generated by TVB-recon, there is a file called average_ orientations.txt, I want to know what this is. Recently, I want to use openmeeg to generate the gain matrix of SEEG. I want to take the center of the brain region as a point dipole, but only the location of the center of the brain region, and openmeeg needs the orientation of the dipole, so I want to know whether the average_orientations.txt can be used as the orientation of the dipole in the center of the brain region.

[maedoc]

That would be possible but only useful for cortical areas.

[nana-zhang]

Hello, thank you for your reply, so can I use center.txt and average_orientations.txt in the output file of tvb-econ to build the source model? I now have the location information of SEEG electrode. I want to use the brain area segmented by tvb- recon and the location of SEEG electrode to construct the gain matrix with openmeeg，but I don't know whether this is correct.

[maedoc]

This can be done, yes, but you'll need to do one of (a) generate all the files and run openmeeg yourself, (b) try/adapt nascent tools like this one or (c) load data in e.g. Brainstorm and have it compute the forward solution.

All this, for sEEG, is quite cumbersome, and again, if you're trying to model subcortical sources, where you don't have good orientation information, it can be just fine to use simple inverse distance rule to compute the contribution, such that the contributions from subcortical and cortical areas aren't too different.

[nana-zhang]

OK, thank you for your reply, but I still have some confusion, centers.txt and average_ orientations.txt should be based on aparc.a2009s + aseg template, and this template includes subcortical structures, so why can it only be used in cortical areas? What is the inverse distance rule？

[nana-zhang]

After reading the openmeeg tutorial, I feel that it is really troublesome to generate all the files by myself. Can I use the header model provided by openmeeg to calculate the gain matrix, as shown below? I found some data about the header model in the openmeeg source code, but I don't know whether it will have a great impact on the accuracy of the results if I use these header models directly。

[maedoc]

There is an example of the inverse distance here. You should read the OpenMEEG tutorial if you want to use their software.