I dont understand why you cannot correct the education and grey matter in a GLM with 3 repeated measurements. how exactly did you do in order to subtract two time points?
Tony
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From: FSL - FMRIB's Software Library [[log in to unmask]] on behalf of Jacobs H (NP) [[log in to unmask]]
Sent: Friday, August 30, 2013 12:30 PM
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Subject: [FSL] Is my approach / argumentation ok or not?
Dear FSLers
I have resting state data of 20 old and 20 young people, measured on three different time points (before, immediately after intervention and a bit later).
In order to analyze my data I did the following: I subtracted time 1 and time2; time 2 and time 3 and performed two-group comparisons on these differences (as mentioned on the list).
The advantage of this procedure is that I was able to correct for education and I could add a voxel-wise covariate for grey matter (due to the age differences).
As I only have one T1 image this seemed to be a nice solution.
One of my co-authors actually believes this model is weak and suggests that I should perform a repeated measures GLM. However, I can not correct for education and grey matter than. I know that the subject-specific EV's account for this, but I thought that this might not capture all the differences.
Could I use the approach that I used or is the repeated measures indeed a better instrument?
Thanks!
Best
Heidi
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Dr. Heidi Jacobs
Postdoc researcher
Faculty of Health, Medicine and Life Sciences
School for Mental Health and Neurosciences
Division Cognitive Neuropsychiatry and Clinical Neurosciences
Alzheimer Center Limburg
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www.maastrichtuniversity.nl
www.heidijacobs.nl
Dr. Tanslaan 12, 6229 ET Maastricht
P.O. Box 616, 6200 MD Maastricht, The Netherlands
T +31 43 38 84 090 F +31 43 38 84 092
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