Antonella Kis wrote:
Dear Freesurfer experts,
I am doing a thickness-age correlation group difference study (patients versus controls. I would like to know if:
- my contrast vector defined as 0 0 0.5 0.5 is correct in order to test the change in thickness with age
Yes.
2)what is the best iteration number for the simulation? Should be 5000 or 1000 or greater?
10,000 -- note that if you're doing a whole-hemisphere correction with the monte-carlo simulation then you should use the pre-computed results (use the --cache option to mri_glmfit-sim)
3)why when I run the simulation for 5 iterations I've got zero clusters?
You should look at your data to make sure that you have actual activation above the voxel-wise threshold you have set. Also, only 5 clusters would not be enough to get a significant cluster anyway.
4)can I derive the thickness from the significant clusters of glm analysis? Do I need to run QDEC after GLM?
If you mean that you want the average thickness from each subject for a given cluster, then this information is generated with mri_glmfit-sim in the csdbase.y.ocn.dat file.
doug
Thanks for any enlightenment. Antonella
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