afni.nimh.nih.gov

Just writing in case anyone knew of a simple way to limit the voxels included in a ttest is to ONLY those voxels common amongst all subjects.
I had been using 3dcalc to create a group mask from individual subject masks and re-applying it to each individual’s data.

This works great but only if you aren't working with an ever-changing group of subjects.

It does not appear that 3dttest does this automatically based on the immediate input.