afni.nimh.nih.gov

> I want to get the p-value for the test statistic for detecting activation at each voxel for the values inside the mask.

You should be to able to see the p-value for t- or F-statistic at each voxel on the AFNI viewer. If you really want to get the whole brain p-values for each statistic sub-brick, you can use 3dcalc with functions such as fitt_t2p(t,a) or fift_t2p(t,a,b), but I usually don't see the point of doing that.

Gang