Hi Chintan
(a) yes, I would think fsaverage would be fine in this age range
(b) we do *not* resample into talairach coords, so volumes and surface areas should include eIV or something equivalent as a covariate. Thickness shouldn't require it.
cheers Bruce
On Tue, 5 Sep 2017, Mehta, Chintan wrote:
Dear FreeSurfer users,
I am new to surface based analysis in FreeSurfer (version 6.0). My data consists of T1-weighted scan from normally developing youth of 8 to 21 years of age. I have two questions on assumptions of this analysis for pediatric data:
(a) Is "fsaverage" an appropriate common template for all subjects of ages 8 to 21? Online tutorials suggest that fsaverage is the most commonly used template in FreeSurfer analyses and, furthermore, imply that FreeSurfer can be used on scans of normally developing children as young as five years old.
I am running analyses separately over different age groups (like ages 8 to 12, 13 to 16, 17 to 21) to ensure robustness. However, would combining results be inaccurate?
(b) Previous posts in this forum and FreeSurfer documentation strongly recommend somehow normalizing for head size or total brain volume in models of ROI area/volume. Would the eTIV covariate also be appropriate for surface-based analysis of scans registered to fsaverage when using mri_glmfit?
To me, it appears that scans registered to fsaverage have been warped to Talairach space, so the whole brain adjustment has been implicitly made.
Thank you in advance for your great insights!
Best,
Chintan