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Hi, Steve. I think it is a wise idea to include the 2nd order derivatives, particularly if your older adult cohort has a history of cardiac, statin use or hypertension-related issues. Inclusion of these derivatives probably should also be guided by your task structure and event timing, but that’s a bit beyond my wheelhouse. Hope this helps, Jeff Duke University Medical Center Div. of Geriatric Behavioral Health > On Apr 29, 2020, at 2:25 PM, Steve Petersen <[log in to unmask]> wrote: > > Dear SPM experts, > > Please, could you give to me some suggestions about my previous email?. > > Thanks for your time. > > Best regards, > > El mié., 22 abr. 2020 a las 17:11, Steve Petersen (<[log in to unmask] <mailto:[log in to unmask]>>) escribió: > > Dear all, > > I am conducting a fMRI study (event-related design) in old adults. As I understand, aging can induce changes in latency and amplitude of the haemodinamuc response (that´s right?). > > Taking into account this, I was wondering if it is a good choice uses the Canonical HRF with time and dispersion derivatives in my first level. More generally speaking, in which cases is it advisable to include derivatives? > > Thank you in advance. > > Best regards, > > Steve.