There are potentially several options; however, based on your wording
of the word "common", I'd recommend the following:
(1) Threshold each subject and make a binary image for each (imcalc: i1>0);
(2) Add up all the subjects in study 1 and threshold (imcalc: X>n,
where n is the number of subjects;
(3) Repeat for study 2;
(4) Now add study 1 and study 2 (imcalc: i1+i2.*2)
This will give you regions common in all subjects in study1, study2,
and study 1 and 2 combined.
-------
Global Conjunction and the Conjunction Null could also be used, but
there intrepretations are different from what you explicitly asked for
in your email.
Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Postdoctoral Research Fellow, GRECC, Bedford VA
Research Fellow, Department of Neurology, Massachusetts General
Hospital and Harvard Medical School
Office: (773) 406-2464
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On Tue, Feb 8, 2011 at 8:19 AM, turki sabrah <[log in to unmask]> wrote:
> Dear SPM users,
>
> I have conducted two experiments and I want to carry out conjunction
> analysis to look at activations that are common to all subjects in these
> studies. Any thoughts or suggestions about which approach should I go with
> and why ? fixed-effect or Random-effects approach (between two studies) ?
>
> Thanks in advance
>
> Turk
>
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