Its hard to say without seeing your contrasts.
In general, one-sample t-tests will test a condition against 0 and the paired t-tests test one condition against another.
If your contrast was 1 or -1 for the one sample tests and 1 -1 for the paired t-tests, I'm not suprised by the differences as you are testing something different with each model. If your contrast for the paired t-test was 1 1, 1 0, or 0 1 plus 2/N or 1/N for each subject column, then you have an incorrect contrast as between subject effects cannot be tested for significance in repeated measure models without writing your own custom code (e.g. GLM Flex by Aaron Schultz and myself). Your statistics are inflated by the use of the within-subject error term for a between-subject effect.
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
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2012/1/11 KimMJ
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Dear experts,
I'm a novice to spm analysis and this is my first trial to perform 2nd-level analysis of fMRI.
My study design included pre-treatment and post-treatment in a group of patients (N=10).
First, I did one-sample t test in pre- and post-treatment sessions, respectively.
Second, I did paired t test (post minus pre) in order to find effect of treatment on brain activation.
Here is my question;
2nd-level analysis using paired t test gave a significant activtion (FWE-correted P<0.05, both voxel- and cluster-threshold) in the superior temporal cortex. However, this region of significant activation is not found in 2nd-level analysis using one-sample t-test in both pre- and post- at the same threshold.
Is this valid? Can I report this temporal cortex as significant and meaningful result?
Thanks in advance for your help.
MJ