Use gPPI: http://www.nitrc.org/projects/gppi
Just specify all your tasks and it will automatically create the PPI
terms for the pmod as well as the task.
The paper describing the method is McLaren et al. 2012 in Neuroimage.
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 Wed, Oct 24, 2012 at 11:34 AM, Rafael Huber <[log in to unmask]> wrote:
> Dear SPM experts
>
> As I understand it, the standard question one would like to answer with a
> PPI analysis is the following:
>
> " Is the connectivity between brain region X and Y dependent on the level of
> the experimental factor A with the two levels 1 (e.g. attention) and 2 (e.g.
> no-attention)?"
>
> Is it alternatively also possible to ask the question:
>
> " Is the connectivity between brain region X and Y higher/lower the
> higher/lower the value in the experimental factor A (which is a vector or in
> other words a pmod)?"
>
> My guess is, that this should be possible, as it shouldn't make a
> difference, if I use a factor with two or more levels to form the
> interaction term. If my guess is correct, how can I implement this in SPM8?
> Is it possible to do this in the same way as in the example in the SPM
> instructions (instructions: 0, -1, 1, ... for attention minus no-attention;
> with pmod: 0, 1, ... where 1 is the pmod)?
>
> Thanks a lot for your help in advance!
>
> Best regards,
>
> Rafael
>
>
> --
> M.Sc. Rafael Huber
> University of Basel
> Department of Psychology
> Economic Psychology
> Missionsstrasse 62a
> CH-4055 Basel
>
> Phone +41 61 / 267 02 98
> E-Mail [log in to unmask]
> Web
> http://psycho.unibas.ch/die-fakultaet/personen/profil/person/huber-rafael/
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