(Please excuse the naivety in these questions). I am getting confused with when to blur data given the new ACF options for clustering. Perhaps I’m confused about smoothing individual subject datasets vs. smoothing 2nd level group analysis for FDR correction? Details below:

I use to pre-process my individual subject’s resting state data. Blur is a default processing block at 4.0mm. Is it ‘correct’ to blur your individual subject data? Also, with the new ACF (instead of FWHM), would this method still be applicable? If I run -regress_est_blur_errts, I get an ACF (final value) of about 2 for each subject. Does this mean I should blur at 2mm rather than 4mm? When I do a seed based analysis, I run 3dDeconvolve and use the ROI as a stimulus file. Then, I run 3dmerge on the resulting file:

3dDeconvolve -input $dset
-mask anat_mask_rs+tlrc’[0]’
-polort -1
-jobs 8 -float
-num_stimts 1
-stim_file 1 ${s}_${ROI}.1D
-stim_label 1 ${ROI}
-tout -rout -bucket ${s}buc${ROI}

#blur at 3mm
3dmerge -doall -1blur_fwhm 3.0 -prefix ${s}_${ROI}blur3.nii.gz ${s}${ROI}.nii.gz

If I don’t blur the individual subject data, at this point, aren’t I only blurring the ROI as opposed to the other brain regions that are correlated with the seed?
I don’t want to over-process my data and I want to make sure I’m using these new/corrected options in the right way in the right place.

Thanks in advance for your help.