Hi Rick,

Thank you for your informative response.

To clarify, I only plan to make comparisons within each class (within anticipation, comparing a fear anticipation to a no fear anticipation; within stimulation, pain stimulation vs. no pain stimulation; the four conditions indicated by separate regressors). I have also decided to add cue to anticipation, so now there are only two classes of stimuli - anticipation (6s, 9s, 12s, or 15s) and stimulation (6s). I've expanded the example below to make this more clear.

So I would include the following in my script, with each of my anticipation times files as single column (global times) with a series of rows with "onset":"duration" and each of my stimulation times file as a single column (global times) a series of rows with just "onset" since duration is constant and set by the BLOCK option?

-regress_stim_times ant_fear_times.txt ant_nofear_times.txt \
stim_pain_times.txt stim_nopain_times.txt \
-regress_stim_labels ant_fear ant_nofear stim_pain stim_nopain \
-regress_stim_types AM1 AM1 times times \
-regresss_basis_many dmBLOCK dmBLOCK 'BLOCK(6)' 'BLOCK(6)' \

Similar question for a different task, in which I have three classes of stimuli, with no duration modulation [block of Faces (all 6.5s), Scenarios (all 9s), and Questions (all 3.5s)] - would the lines below be appropriate, with each regressor file just being a single column (global times) with rows of onset times for each stimulus?

-regress_stim_times face.txt scenario.txt question.txt \
-regress_stim_labels face scenario question \
-regress_stim_types times \
-regresss_basis 'BLOCK(6.5)' 'BLOCK(9)' 'BLOCK(3.5)' \

This is a simplified example since there are multiple conditions within each stimulus class, but I would only be making comparisons within each stimulus class, so the blocks of different lengths are ok?

One last question - I know this is covered in the help for 3dDeconvolve but I don't quite understand it - what is the consequence of excluding the 1 from BLOCK or dmBLOCK [e.g., using BLOCK(6) instead of BLOCK(6,1), or just dmBLOCK instead of dmBLOCK(1)]?

Thank you again for your time and assistance!

Sincerely,
Kristin