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Hi Ben > > Dear SPM users, > > I'm running an experiment where the subjects has to choose between two > options in a cognition task. In addition they are playing sometimes > against a real counterpart or sometimes against the computer. Now I > want to analyze the imaging data and designed a matrix with the four > conditions: computer_option1 and computer_option2 and human_option1 > and human_option2 with their onsets and durations. I also added for > parametric modulations the reaction times for the different options > with a first order polynomial expansion. I have a TR of 2.5 s and 37 > interleaved slices, so I used 37 for microtime resolution and 18 for > microtime onset. Is this a good design for the first level analysis? > And how should I create the contrast that I can also make a good > second level analysis? > I would also specify it's a factorial 2*2 design otherwise that looks pretty good to me .. As for 2nd level analysis, it depends on which school you are FH approach: compute all effects within subjects (computer/human [1 1 -1 -1] option1 / 2 [1 -1 1 -1] inrteraction [1 -1 -1 1]) and do a one sample t-test for each contrast Var comp approach: don't bother with contrasts (unless you have several sessions then simply make a contrast per condition) and enter the 4 beta/con maps per subject into a repeated measure ANOVA (flexible factorial) Hope this helps Cyril -- Dr Cyril Pernet, Academic Fellow SBIRC fMRI Manager SFC Brain Imaging Research Center Division of Clinical Neurosciences University of Edinburgh Western General Hospital Crewe Road Edinburgh EH4 2XU Scotland, UK [log in to unmask] tel: +44(0)1315373661 http://www.sbirc.ed.ac.uk/cyril http://www.sinapse.ac.uk/