Li,
Your question will be easier to answer with more experimental design
details. However, if you are doing a fixed effects group analysis and
want to do a conjunction across subjects, you do not have to process
each subject differently. What you should do is enter all subjects into
a single design matrix and enter the contrast of interest for each
subject. After you have done this, you can than perform a conjunction
analysis be holding down the "control" key and selecting each of the
subjects' contrasts.
A good reference for using conjunction analyses for group data is:
Friston, K.J., Holmes, A.P., Price, C.J., Buchel, C., Worsley, K.J.
Multisubject fMRI studies and conjunction analyses. NeuroImage 10,
385-396 (1999).
Hope this helps,
Paul Laurienti
Li Tianhao wrote:
> Dear SPMers:
>
> I met a problem when I did the group analysis.
> As you know, some subjects have stronger activity and some
> only have weaker response in the similar tests.
> So there are no uniform thresholds across all subjects.
>
> My question is how to process the different intensities' threshold
> of different subjects while doing conjunction analysis?
>
> Thanks
> Tianhao
>
> _________________________________________________________________
> Get your FREE download of MSN Explorer at http://explorer.msn.com
|