=?iso-8859-1?Q?Rachel_Kozink?= a écrit :
>SPM experts,
>
>I am a first time user of SPM and wanted to double-check my design to
>ensure that I am performing my analysis correctly, especially since I am
>not getting the results that I had anticipated. I am using SPM2.
>
>Our study has 7 subjects so far (we are in the middle of the study and
>trying to analyze what we have so far to use as pilot data). Each subject
>is scanned twice and has condition 1 (C1) on one day and condition 2 (C2)
>on the other day. On each day, the subject performs two runs of the same
>task, which has two block conditions (A and B).
>
>I performed a first level analysis for each subject on each visit (e.g.
>Sub1, C1). I created contrast images that contrasted block A versus block
>B. I then took these contrast images and entered them into a paired t-
>test, where a pair consisted of 1) A-B contrast image for C1 and 2) A-B
>contrast image for C2.
>
>Just to clarify, it is my understanding that the p value and voxel extent
>thresholds you put in for the t-test after the first level analysis has no
>bearing on the con_* image that is created and used in the second level
>analysis. Is this correct?
>
>
Yes it is, the con images are the linare combinations of you beta images
- spmT images are the resulting statistical maps
>I am performing no masking and using very liberal p-values and cluster
>values and am still not seeing much activation. Does this mean that my
>data just doesn't have any significance or am I doing something wrong?
>
>
Everything looks ok to me - did you try with a single matrix per subject
par the 2 sessions?
Note also that 7 subjects may be not large enough to 'see' smthg - as it
is pilot data you can try to make one matrix (1st) with all subjects and
sessions ..
Best
Cyril
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