Hi Dr Greve,

I would like to correct surface based analyses of PET data for multiple comparisons. I ran group comparisons in three spaces. left and right hemispheres and subcortical.

I used the method --cache in mri_glmfit-sim to correct the analyses in eft and right hemispheres.

I used the method --grf in mri_glmfit-sim to correct the analyses in subcortical regions.

My questions are:

In one of your kind responses to a collegue here https://mail.nmr.mgh.harvard.edu/pipermail//freesurfer/2014-January/035650.html

you had suggested  "If you want to use GRF, you should use smooth by twice the native voxel size. I would not go higher than .01 on the threshold".

Would you mind clarify what it means don;t go higher than .01 is this the cwp threshold? also smoothing by twice the native voxel is this means fwhm=2mm?

The methods --cache and --grf are giving me the expected results.. when  I should consider using simulation --perm ?

Thanks for any clarification

John