Dear Ping,
The long answer:
I suggest you read chapter 8 from Human Brain Function 2nd edition (http://www.fil.ion.ucl.ac.uk/spm/doc/books/hbf2/ ) on statistical inference and the meaning of contrast vectors, looks like you first might want to get into fMRI statistics. It's worth it. The answer to your question greatly depends on what you want to know ...
By the way, I do not think your design has enough repetitions to show much activation reliably ...
The short answer: try '1' ...
Good luck,
Bas
--------------------------------------------
Dr. S.F.W. Neggers
dept. of Psychonomics,Helmholtz Institute
Utrecht University
Heidelberglaan 2
3584 CS, Utrecht, room 17.09
the Netherlands
Tel: (+31) 30 253 4582 Fax: (+31) 30 2534511
E-mail: [log in to unmask]
Web: http://www.fss.uu.nl/psn/pionier
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-----Oorspronkelijk bericht-----
Van: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]]Namens Wang Ping
Verzonden: maandag 26 september 2005 23:36
Aan: [log in to unmask]
Onderwerp: [SPM] for this situation, how should I define the contrast vector?
Urgentie: Hoog
Dear SPMers:
Suppose there's a very simple experiment: one subject/one session, TR = 1s,
total 100 volumns, 1 slice/volumn. The stimulation is like this:
____________
____________________| |_____________
1 50 80 100 (second, or volumn)
After I performed design matrix under spm2, I want to know in "Select
contrasts", how should I define a new contrast (what is the vector for T/F
contrast)? I am a beginner, really don't know much about it.
Also, I find under spm2, I cannot define a contrast, I don't know why.
Is there anyone kindly help me? Many thanks!
Best,
Ping
