There are a couple of things that come to mind. - Are you sure you have the same GLM in both analyses? - It might not be the thickness that is changing. Try looking at the jacobian, curvature, and/or gyrfication - Examine the individual VBM results carefully to make sure that they are not being driven by an outlier and that the segmentation looks ok. - Voets, 2008, NI did a comparison where they looked at some of these issues.
doug Allison Stevens wrote: > Fatima, > I can't really say anything on this topic but I did want to point you to > some information on FreeSurfer vs. VBM: > http://surfer.nmr.mgh.harvard.edu/fswiki/UserContributions/FAQ#Q.WhataretheadvantagesofFreeSurferoverVBM.3F > > Allison > > On Fri, 8 Jul 2011, Ahmed, F, Me <fah...@sun.ac.za> wrote: > > >> Hello, >> >> I'm wondering if anyone could help me out with a question I had. For a study >> I'm working on, I'm comparing the regional brain volumes in adolescents with >> and without PTSD. I ran VBM analysis and Freesurfer on my subjects and I >> found some significant results on VBM (however, only using uncorrected p >> values) and on Freesurfer, I found no group differences in brain regions. Is >> there an explanation for that? >> >> If anyone has any thoughts I'd really appreciate it. Thank you kindly! >> >> Fatima >> >> >> >> > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > > -- Douglas N. Greve, Ph.D. MGH-NMR Center gr...@nmr.mgh.harvard.edu Phone Number: 617-724-2358 Fax: 617-726-7422 Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting FileDrop: www.nmr.mgh.harvard.edu/facility/filedrop/index.html _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer The information in this e-mail is intended only for the person to whom it is addressed. If you believe this e-mail was sent to you in error and the e-mail contains patient information, please contact the Partners Compliance HelpLine at http://www.partners.org/complianceline . If the e-mail was sent to you in error but does not contain patient information, please contact the sender and properly dispose of the e-mail.
