[Freesurfer] vertex coordinates: tksurfer vs sig.cluster.summary

Dear Freesurfers,

I have noticed a slight incongruity between the coordinates outputted by sig.cluster.summary and those in tksurfer.

For instance, in the .summary file one of my maxima (VtxMax=92221) has the following "Tal" coordinates: -14.9, -62.2, 57.5.

Now, if I open the fsaverage with tksurfer, and I enter 92221 as my Vertex Index, the Vertex Talairach coordinates are slightly different than those reported by the .summary file (-14.89, -61.61, 57.01). Is this because the Max in my significant cluster actually spans multiple adjacent vertices, and therefore the coordinates provided by the .summary file represent an average across those vertices?

As for the "MNI Talairach", my understanding is that these are from the MNI305, right? If so, why the "Talairach" part of the name?

Thanks,

Marco

_____________________

Marco L. Loggia, PhD

Postdoctoral Fellow, Mass General Hospital & Brigham and Women's Hospital

Harvard Medical School

CNY Building 120, suite 101E

Charlestown, Massachusetts 02129

Phone: (617) 643-7267

Fax: (617) 643-7340 marco@nmr.mgh.harvard.edu