Thanks Gang, I must have been looking at the wrong section where it explains each basis function.
Regarding the duration, 3dDeconvolve help shows you can add the stimulus duration to the modeling for SPMG. For example, if you have a 6-second stimulus, you could enter SPMG(6). I was wondering if the output has the duration modeled separately, but after looking at it, I see it doesn't.
Thanks!
-Danny