Dear FSL list,
I was wondering whether you would be able to advise me on the correct procedure, such as setup of the design matrix for a paired t-test TBSS analysis. But more importantly, advise me how to setup an analysis where I can regress age, education, or a continuous clinical variable on the change oberved between two time points.
For example, I have 10 participants assessed at two time-points. The first step would to be to see whether indeed there is change in FA (but could also check the eigenvalues, RD, etc...) between the two time-points.
Using the Glm Wizard for paired t-test I used the default matrix and contrasts (based on 10 participants at two time points):
Group EV1 EV2 EV3 EV4 EV5 EV6 EV7 EV8 EV9 EV10 EV11
A>B s1 s2 s3 s4 s5 s6 s7 s8 s9 s10
1 1 1 0 0 0 0 0 0 0 0 0
1 1 0 1 0 0 0 0 0 0 0 0
1 1 0 0 1 0 0 0 0 0 0 0
1 1 0 0 0 1 0 0 0 0 0 0
1 1 0 0 0 0 1 0 0 0 0 0
1 1 0 0 0 0 0 1 0 0 0 0
1 1 0 0 0 0 0 0 1 0 0 0
1 1 0 0 0 0 0 0 0 1 0 0
1 1 0 0 0 0 0 0 0 0 1 0
1 1 0 0 0 0 0 0 0 0 0 1
1 -1 1 0 0 0 0 0 0 0 0 0
1 -1 0 1 0 0 0 0 0 0 0 0
1 -1 0 0 1 0 0 0 0 0 0 0
1 -1 0 0 0 1 0 0 0 0 0 0
1 -1 0 0 0 0 1 0 0 0 0 0
1 -1 0 0 0 0 0 1 0 0 0 0
1 -1 0 0 0 0 0 0 1 0 0 0
1 -1 0 0 0 0 0 0 0 1 0 0
1 -1 0 0 0 0 0 0 0 0 1 0
1 -1 0 0 0 0 0 0 0 0 0 1
Contrasts:
EV1 EV2 EV3 EV4 EV5 EV6 EV7 EV8 EV9 EV10 EV11
Condition A> B 1 0 0 0 0 0 0 0 0 0 0
Condition B> A -1 0 0 0 0 0 0 0 0 0 0
This matrix and contrast setup was used with this randomise statement:
randomise -i all_FA_skeletonised -o tbss -m mean_FA_skeleton_mask -d design.mat -t design.con -n 1000 --T2 -V
So firstly, have I set up the matrix, contrast, and randomise statement correctly for this analysis. That is, comparing time1 vs time 2 on FA?
Secondly, and perhaps the more complex analysis, I am trying to then see whether the change between time 1 and time 2 is associated with change on clinical measures over the same time-points.
What is the best way to get TBSS to correlate the change FA values with the change in clinical measures?
Thank you in advance for any assistance that you are able to provide me.
Regards,
Gershon.
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