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For within-subject designs, you should use the flexible factorial design and include a subject term to properly account for subject effects.

The contrasts are correct.

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, Nov 29, 2011 at 10:22 AM, Marjorie Dole <[log in to unmask]> wrote:
Dear SPM users,

I have a question concerning second level analysis:

I have an experimental design with three conditions, A, B, C, and a baseline. I want to evaluate fMRI activations specifically for each condition versus the two others in my whole group, by testing the contrasts : A-(B+C), B-(A+C) and C-(A+B).

So I did for my first level analysis the following three contrasts: A-baseline, B-baseline and C-baseline.
At the second level I used a full factorial design with one factor (Condition; three levels: A, B, C) and then I contrasted each condition versus the two others using the following contrasts : 2 -1 -1 ;  -1 2 -1;   -1 -1 2.

Is this approach valid?
Do you have any suggestion?

Thanks for your help,

Marjorie