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Dear SPM experts! Sorry if I repeat my question. I would be very grateful for any advice regarding this issue. So I am trying it again... We are performing a bloc design fMRI experiment with 4 sessions/subject (100 scans/session TR 3 sec). Each session consists of 10 blocs (each of ~10 scans length, slightly varying, exact bloc lengths are entered in the Design matrix) The order of conditions is as follows: session 1: E C B D A C A D E B session 2: A D B C E B E D A C session 3: B A E D C B E A C D session 4: C D E A B A E B D C where A-D are four different 'active' conditions and E is a 'rest' condition. we are interested in the effects of each individual condition A-D against rest (1 0 0 0 -1, 0 1 0 0 -1, 0 0 1 0 -1, 0 0 0 1 -1) conditions AB / CD against rest (1 1 0 0 -2, 0 0 1 1 -2) and differences of activation between the 'active' conditions A-D (1 1 -1 -1 0, -1 -1 1 1 0, 1 -1 0 0 0, 1 0 -1 0 0 ....). We built a design matrix with 5 different conditions, variable SOA's and variable durations, defining the blocs as events of different length, basic function 'hrf only'. SPM now offers us a default high pass filter of 177 213 176 152 sec. We do not really understand how these cut offs are calculated and why they differ that much between sessions. (if it is calculated as twice the minimum of the maximum interval between corresponding conditions as mentioned in earlier mails we would for example suppose a cut off of 2 x 20 scans x 30 sec = 120 sec [interval between two periods of condition A] for session 1 and 4). In our study all conditions appear twice. Which condition determines the high pass? The one which has the shortest interval between condition specific blocs? (A in sessions 1,4; E in sessions 2,3?) Thank you very much for your help Bernhard Dr. B. Haslinger Neurologische Klinik TU München Möhlstraße 28 D-81675 München E-mail: [log in to unmask]