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Dear all, We performed an fMRI study with a patient and a control group, using a specific movement task. We performed simultaneous recording of a behavioural measure. This parameter was significantly different between groups. Now, we would like to know whether brain activation specifically related to this parameter is different between the patients and healthy subjects, thus on second level. We first tried a two-sample t-test and using the parameter as 2 covariates, one for each group (padded with zeroes), which is the conventional method for investigating the effect the possible role of a covariate when comparing activation of two groups. However, because our parameter is not just a covariate as body mass or bloodpressure as in normal statistics, but measures actual motor output, which should be organized by the brain, we figured we also could use a single t-test. This way, we do not model group-differences, since we actually are only interested in differences brain activity related to this covariate in the two groups. I hope someone can give me some advice whether this is a correct thought???? Thank you very much!! Best regards, Carolien Toxopeus, MD, PhD student