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You want the SPM.Sess(s).P field. the numbers can be anything, 1 for each onset vector. However, this only will work for each onset of a regressor, not TR. Modulating each TR doesn't really make sense from the point of a GLM. Cheers, Michael On Tue, Jul 26, 2011 at 1:48 PM, Watson, Christopher < [log in to unmask]> wrote: > Are you talking about doing parametric modulations? What's your task? > ________________________________________ > From: SPM (Statistical Parametric Mapping) [[log in to unmask]] On Behalf > Of Cinly Ooi [[log in to unmask]] > Sent: Tuesday, July 26, 2011 3:28 PM > To: [log in to unmask] > Subject: [SPM] Varying the weight for 1st level design matrix > > Dear All, > > Someone asked me to run a first level analysis where instead of a standard > boxcar or event design, I have a weighting value associated with each TR. I > believe what I have to do is to set the onset time and duration as usual, > then assign a weight to each onset time.i.e., instead of accepting the > standard weight of '1,1,1,1', I want to specify them as '2,1,1,2' for > example. > > Since each session will have its own unique weights, for ease of data > entry, I will be reading the weights from files and will be processing the > data using Rhodri's AA. > > A bit of digging into AA shows that I have to setup this up using > SPM.Session(s), and I believe SPM.Session(s).U is the candidate to accept > the weights. My problem is, after reading spm_FMRI_design.m, I still have no > clue how to set the weight. > > How do I go about setting the weights? These weights are expected to be > convoluted with HRF later. > > In case it helps, it is one weight per volume. So since I have 224 volumes > in the fMRI time series, I will have 224 weights to put in. > > Many thanks in advance and hope to hear from you soon. > > Best Regards, > Cinly > -- Research Associate Gazzaley Lab Department of Neurology University of California, San Francisco