So if you have multiple thresholded maps combined with a mask, you can compute a conjunction test with 3dcalc like this
3dcalc -a 'func+orig[12]' -b 'func+orig[15]' -c 'mask+orig' \
-expr 'step(a-4.2)*step(b-2.9)*step(c)' \
-prefix compound_mask
Then follow it with any of the previous examples to count the number of voxels like this:
3dBrickStat -count -non-zero compound_mask+orig
The 3dcalc command is from 3dcalc -help example number 5. You might want to see the other examples there for more ideas on how to do various conjunction tests.
