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Thank you Anderson The reason that I don't want to use subtractions is because the design is an event-related one and the signal is very week. I have analysed using valence in FSL. I have used event type as valence in my regressors. for example in my four regressors I have: 1- timing of block A with *valence=1* for Go (one of my event types) and *valence=-1 *for Nogo. 2- timing of block A with *valence=1 *for Go (one of my event types) and *valence=1* for Nogo. 3- timing of block B with *valence=1* for Go (one of my event types) and *valence=-1* for Nogo. 4- timing of block B with *valence=1* for Go (one of my event types) and *valence=1* for Nogo. Then if I choose my contrasts as EV1-EV2 will I get what I want? how do you see this method? On Fri, Oct 16, 2015 at 11:39 AM, Anderson M. Winkler < [log in to unmask]> wrote: > Hi Ashkan, > > I think Greg's suggestion is a sensible one. Why you'd like not to do > subtractions? > > Also, it might help if you typed the names of the EVs in the email -- it's > a bit difficult to read from the labels and be sure we are all talking > about the same thing. > > Thanks. > > All the best, > > Anderson > > > On 15 October 2015 at 09:26, Ashkan Faghiri <[log in to unmask]> > wrote: > >> Thank you Greg for your answer, >> >> but I don't want to use subtraction. I am looking for a way to do this >> with valence in fsl. dou you think my strategy is wrong? >> >> >> >> >> On Tue, Oct 13, 2015 at 5:55 PM, Greg Burgess <[log in to unmask]> wrote: >> >>> Hi Ashkan, >>> >>> With your design, I would create eight 3-column EVs, with each EV coding >>> the duration of the 'C' events within their respective 'B' block. >>> i.e., Eight separate EVs for B1_C1; B1_C2; B2_C1; B2_C2; B3_C1; etc... >>> >>> Then, I would code different contrasts for the effects that you're >>> interested in. >>> B1_C1 - B1_C2: difference between C1 and C2 during B1 block >>> B2_C1 - B2_C2: difference between C1 and C2 during B2 block >>> (B1_C1-B1_C2)-(B2_C1-B2_C2): interaction of (C1-C2) difference as a >>> function of block 1 versus block 2 >>> : just to be clear, this contrast would be coded >>> [+0.5, -0.5, -0.5, +0.5, 0, 0, 0, 0] >>> >>> --Greg >>> >>> ____________________________________________________________________ >>> Greg Burgess, Ph.D. >>> Staff Scientist, Human Connectome Project >>> Washington University School of Medicine >>> Department of Anatomy and Neurobiology >>> Phone: 314-362-7864 >>> Email: [log in to unmask] >>> >> >> > -- -- Ashkan Faghiri MSc student of Bioelectrical Engineering Department of Electrical Engineering Sharif University of Technology