afni.nimh.nih.gov

Since your model is

Y = a + b*X + e

the sub-bricks #0 and #1 in your 3dttest++ output are for the intercept 'a' in the model above, which is the group average effect that is associated with the average value of X ('bprstot' in your case), and the sub-bricks #2 and #3 in your 3dttest++ output are for the effect of 'bprstot'.

For your 3dMVM script, check if there is some extra space after the backslash on the following line:

Subj bprstot InputFile \

Gang