Hi AFNI,

Can you please clarify a few things about the -stim_times_AM1 option in 3dDeconvolve? I'd like to specify the HRF with duration modulation, but not amplitude modulation. My stim time files have stimulus onsets married to the participant's RT (stimulus onset*RT). When I run 3dDeconvolve, the log spits out the average amplitude for each regressor. With this format, am I modulating the duration or the amplitude? For duration modulation, should my stimulus onsets and RTs be married with a : instead of a *?

Part of my confusion comes from looking back through an old message board thread. The user was running duration modulation with SPMG2, so that AFNI calculates coefficients for both the regressor and its temporal derivative. I notice that the user was getting four coefficients per condition, which represented the coefficient for the regressor, its temporal derivative, the RT, and the RT's temporal derivative. When I run 3dDeconvolve with the -stim_times_AM1 option below, I only get two coefficients per condition, which I assume are for the regressor and its temporal derivative. Is there a reason I'm not getting coefficients for the RT and its temporal derivative?

-stim_times_AM1 5 ${subj}.Emo_Angry_Standard_ALL.1D 'SPMG2' \

Thanks for the help,
Phil