afni.nimh.nih.gov

Dear Daniel and peter
My fmri data is in MNI space(warped into mni with the help of fsl).However,as I convert the "nii" format to "HEAD/BRICK" it leads to "image+orig.BRICK/HEAD".So I thought maybe the "orig" refers to MNI space.Could you please tell me what "orig" refers to?I am a little confused.
Many thanks in advance.