hi Corey-

There's many ways to do this, but here's how I would: 1.transform the talairach coordinates to RAS (using some transform you have already determined), that's what the surface vertices are in. You probably want to use the pial surface. [vert_coords]=read_surf(SURFFILE);

2.for each electrode coordinate, find the index of the nearest vertex by calculating the euclidean distances to each point on the surface. [~,I]=pdist2(vert_coords,elec_coords,'euclidean','Smallest',1); %pdist2 is only available in newer versions of matlab, it's trivial to write your own as well

3.use these indicies to then get the roi from the actbl: [averts,albl,actbl]=read_annotation(APARCFILE); for a=albl(I)', elec_rois{a}=actbl.struct_names(find(actbl.table(:,5)==a)) end

-- brian

On Mon, Jul 18, 2011 at 9:38 PM, Corey Keller corey.j.keller@gmail.comwrote:

Hi Freesurfers,

I have talairach coordinates of electrodes sitting on the brain. I am hoping to use the Desikan-Killiany parcellation scheme to determine which cortical region each electrode lies closest to in standard space. I am using read_annotation in matlab to read the lh.aparc.annot file and find the vertices associated with each label. I am wondering how to determine which label each electrode lies closest to? Is there a TAL or RAS to vertex function in matlab? Thanks.

Best, Corey _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer

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