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> I've been trying to obtain the time course of activation. First of all I'm > not sure, if the length of my time bins should equal the TR (3 sec) or if it > would be wiser to choose shorter bins of, lets say, 2 sec? Time bins should > cover the period from 5 time points before to 5 time points after the onset > of the condition so that the whole time course should cover 30sec. > Since SPM 2 no longer offers the distinction beween "event related" and > "epoch related" designs I'm not quite sure how to specify the design if I do > not want to convolve my data with the canonical HRF. Which basis set should > I choose for the model setup? FIR model? If so what about the window length > (30?), order (10?) and duration (0?)? Yes, yes, yes! (if you want a bin size of 3s). The first FIR bin will start with the event onset, so if you want to start 5 timepoints before the "true" event, then subtract 15s (5 TRs) from your onset vectors (but note that SPM2 will not handle negative onsets less than -2 TRs, so you may have problems for the first event). There is no point having FIR bin sizes less than your TR unless you have achieved a higher effective sampling rate by jittering your event onsets with respect to the scan onsets, either randomly or by ensuring that your SOA is not a simple multiple of your TR. (So if you locked your event onsets to scan onsets, then there's no point having a bin size less than 3s in your case). HTH Rik