It should be preserving total surface area. Can you send your
mris_preproc command line and the terminal output? It might be something
with 5.1 as well.
On 8/9/18 3:49 PM, Derek Sayre Andrews wrote:
External Email - Use Caution
Dear Freesurfer Developers and Experts,
I have been exploring various vertex wise (mass univariate) effects
using freesurfer measures of cortical thickness and surface area in a
cohort of toddlers/children aged 25-70 months.
When looking at the effect of age on surface area using individuals’
measures mapped to fsaverage and smoothed at 15mm fwhm (area.pial.
fwhm15.fsaverage.mgh) I observed a widespread negative effect of age
(i.e. decreased surface area with age). Given the age group of the
cohort this seems implausible. Plotting the sum of each individuals
lh+rh.area.pialfsaverage.fwhm15.mgh against age shows the relationship:
cid:image001.png@01D42FCE.C197B360
However, plotting the lh+rh total surface area returned by
mris_anatomical_stats reveals a much more plausible relationship
between surface area and age:
cid:image002.png@01D42FCE.C197B360
My working hypothesis is that the significantly smaller brain sizes of
our cohort compared to fsaverage, and the fact(?) that -qcache does
not preserve global surface area, is causing an “over adjustment” in
our cohorts smallest brains when mapped to fsaverage.
Thus, my questions are three fold
1. Is the mapping of our significantly smaller brains to fsaverage a
potential explanation for the results we are seeing in our mass
univariate analyses of surface area?
2. If this is the case, would this effect be limited to surface area
or also extend to other freesurfer measures including cortical
thickness, lGI, sulcal depth etc.
3. How would you recommend approaching vertex wise analyses in a
cohort of this age? Create a study specific average subject using
make_average_subject to map onto?
Thank you for your insight and guidance!
Best, Derek
PS: All processing was performed using freesurfer v5.1
cid:image003.png@01D42FCE.C197B360
*Derek Sayre Andrews, PhD*
Postdoctoral Scholar
Department of Psychiatry and Behavioral Sciences
The M.I.N.D Institute
University of California Davis
Telephone: +1 916 703 0360
Email: dandr...@ucdavis.edu <mailto:dandr...@ucdavis.edu>
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