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Dear SPMers, I have a question concerning the use of regressors in SPM. My goal is to analyze a process which may describe brain activity in some regions. I enter the values of this process as regressor in the batch editor (with one value for each scan). As the regressors are not convolved with the HRF I shift the regressor about 4.5 seconds (delay). Now, I also want to allow for small proband- and voxel-specific shifts in the delay. Applying the HRF this is done via time and dispersion derivatives. As my process regressor is not convolved with the HRF I cannot use this possibility. Do you know any method I could use to incorporate this kind of variability in probands and voxels into my process regressor design? Many thanks in advance!