afni.nimh.nih.gov

I would do something like this:

3dbucket -aglueto sample.nii subject1.stats_REML+tlrc.HEAD[stim1#0_Coef] \
subject2.stats_REML+tlrc.HEAD[stim1#0_Coef] \
... \
subjectX.stats_REML+tlrc.HEAD[stim1#0_Coef]

Or you could use a for loop in bash (or other scripting language):

for aSubject in subject*.stats_REML+tlrc.HEAD
do
       3dbucket -aglueto sample.nii ${aSubject}.stats_REML+tlrc.HEAD[stim1#0_Coef]
done