Concatenating can also cause problems with the AR(1) estimation as
well as the high-pass filtering. For these reasons, people generally
don't concatenate their data.
Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Research Fellow, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School
Postdoctoral Research Fellow, GRECC, Bedford VA
Website: http://www.martinos.org/~mclaren
Office: (773) 406-2464
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On Fri, Nov 9, 2012 at 12:06 AM, Amy <[log in to unmask]> wrote:
> Hello,
>
> I'm running an fMRI analysis with four different runs. I'm concatenating the four runs into one long run in my design matrix (I realize this is not recommended). I created four different regressors to model each of the four runs (using dummy coded 1s and 0s).
>
> Because these four regressors add up to the constant term (which is automatically created in SPM), they are not estimable. The boxes are grey below these regressors when reviewing the design matrix.
>
> I don't care about specific session effects, but I want to make sure that this is okay (i.e. my betas for the events of interest are valid).
>
> Do I need to remove the constant term?
>
> Thanks for any advice!
>
> Amy
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