I am trying to understand why the vertex number shown in the .vertices field in the STC file are placed in a very specific order. Does anyone know what this order represents? My impress is that it may reflect the adjacent information, but I can't be sure. If anyone know, please do help me because I would like to use this information.
The vertex numbers correspond the the initial tesellation of the surfaces
that Freesurfer does (which you subsample to make your source space).
However, in the process of making topological correction to the surfaces,
Freesurfer adds/removes vertices as needed. Because of this there is no
simple relationship that I am aware of between the vertex number and
adjacency.
The documentation for 'mne_add_patch_info' and for the 'surf' MATLAB
structure might be helpful if you are interested in using topological
information for your purposes.