afni.nimh.nih.gov

Offhand, I don't really use global signal so I am not sure and don't have an example handy, but it is useful to note that afni_proc.py creates a script (default name: proc*) so that these things can be investigated by the user in detail. The script is even commented.

If you add your specific AP command here we could look at it to see, as well.

--pt