Thank you Doug,
Exactly! I meant GM near the CC.
When I used "projfrac=0.5 " there was no differnce between the groups at "cwp 0.05", and when I changed the "projfrac to 0" I got significant differnce between the groups in specific areas at "cwp 0.01". Kindly, how can this be explained? I highly appreciate if you help me to understand this point:
For "projfrac =0" I expect the surface based analysis to be running close to white matter. Right? and when I used "projfrac=0.5" the analysis is running in the middle area between pial and white. When the analysis is not showing any differne between the groups for "projfrac 0.5" and showing differnce for "projfrac 0" that means the differnce between the groups is deeper and closer to white matter. Is this correct?
Thank you for any input and clarification!
Bests,
John
John
Sent: Tuesday, January 10, 2017 at 10:51 AM
From: "Douglas Greve" <gr...@nmr.mgh.harvard.edu>
To: freesurfer@nmr.mgh.harvard.edu
Subject: Re: [Freesurfer] surface based analysis (projfrac)
From: "Douglas Greve" <gr...@nmr.mgh.harvard.edu>
To: freesurfer@nmr.mgh.harvard.edu
Subject: Re: [Freesurfer] surface based analysis (projfrac)
When you say in the corpus callosum, do you mean in WM? The surface-based analysis is only for cortical GM. If you mean in GM near the CC, then the analysis is appropriate. The projfrac parameter sets the sampling location between the white and pial surfaces where 0.5 means half way.
On 1/10/17 8:07 AM, John Anderson wrote:
Dear FS experts,I am working on surface based analysis using freesurfer. I want to inquire about the flag "projfrac" in the command "mris_preproc"I ran voxel wise analysis including the same subjects. I found differnce between the groups in areas close to the corpus callosum. I want to get the same results using surface based analysis. If I use the projfrac=0.5 is this able to show the same results that I got in voxel wise analysis at the level of the corpus callosum. Do I need to use differnt number for projfrac ?Thank you for any advice.
Best,
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