Dear AFNI experts,

I am trying to use 3dClustsim on a 3dLME or 3dMVM output to do multiple comparison corrections. I know that first I have to use 3dDeconvolve to get the error time series (errts) from each participant. Then, I should use 3dFWHMx with the -acf option to estimate data smoothness and use those parameters in 3dClustsim.

I have some questions about this process:
Firstly, errts is an output from a regression performed by 3dDeconvolve. So, what can I do if I did that regression using 3dDentred? Can I get the errts in an isolated step? if so, should I input each subject 3D+time image before any detrend with the same regressors than in 3dDentred? Is it possible to get errts file without using regressors? I also would like to understand why is necessary to use errts instead the regressed 3D+time image to get acf parameters.

Secondly, when I use 3dFWHMx I get four parameters which appear in the terminal. Are these parameters the average across all volumes/subbriks? Should I put the first three in acf option when using 3dClustsim then? My last question about this topic is, if I get every subject acf parameters, should I put the mean of all these inter-subject acf parameters with the tstat map as an input (using 3dClustsim) ?

If you could help me with these queries, I would greatly appreciate it.

Thanks a lot,

Karel