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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