Hi, Rick.

I have similar question regarding to DTI group analysis. What I have done for a DTI group analysis was,
1) After motion correction, FA maps were calculated from a native (2.5mm)3 voxel size, without any smoothing
2) Individual FA maps were normalized and re-sampled with 1mm3.
3) FWHM 4 mm Gaussian smoothing was applied before voxel-wise analysis, and we got some result.

To correct a false positive finding, we'd like to run Alphasim with proper inputs.
How can I estimate the smoothing kernel size using 3dFWHMx?

The below is that I did
1) I picked a subject randomly, and b=1000 images were motion-corrected.
2) b=1000 images were normalized / resampled with 1mm3
3) 4 mm Gaussian filtering was applied.
4) run 3dFWHMx -input {b=1000 images} -detrend

Thanks.

-Wanyong