The fwhm.dat is computed from your data and reflects all the spatial
correlation in your data, not just the smoothing you imposed. It is
usually the case that there is some inherent smoothness and so the
total smoothness is more than what you apply. This may be due to an
outlier or just that some areas don't fit the GLM that well (which will
create correlation). It could be that one or more subjects have a global
thickness that tends to be less than the rest of the subjects. Some
modalities (eg, gyrification) also tend to have very high inherent
spatial correlation.
doug
On 8/18/14 11:42 AM, Vy Dinh wrote:
Dear Surfers,
While running a mri_glmfit-sim (monte carlo simulation) for roi
analyses generated using mri_glmfit, I encountered the following error
code:
ERROR: cannot find
/Applications/MRI/freesurfer_5.30_x86_64/average/mult-comp-cor/fsaverage/lh/cortex/fwhm31/abs/th13/mc-z.csd
I checked the fwh.dat file within my glm/ directories and realize that
there is a discrepancy between the fwhm I set for the analyses and the
fwhm in this file (which explains why I encountered the error above.)
Can someone explain why there is a large discrepancy for these roi
analyses (which is specified using the --label option)? What kinds of
things can I do to run the monte carlo simulation appropriately?
Thank you,
Vy Dinh
MD Candidate, Class of 2017
University of Wisconsin School of Medicine and Public Health
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