Dear Stephen,
Many thanks for your reply! I am still working on the test run on mouse and will let you know once I have the outcome.
At the same, I run into some confusion about randomise regarding to demean continious covariable, such as age. And your help will be highly appreciated!
I found this from Jeanette A Mumford's webpage:
"Also important is that if you have multiple groups (see third model example) you should not mean center within each group separately. The reason for this is that your continuous covariate may actually describe some of the group differences, and then mean centering within group will remove this important aspect of the covariate. For example, if you have two groups and one is significantly younger than the other, this difference in ages between groups may explain brain activation differences. If you mean center age within each group, then each group's set of ages will be centered about the same value, 0, and then you risk detecting group differences that are actually just attributable to age. "
On the other hand, I found your previous response to similar question as follows:
"If you want the most flexible modelling, to soak up age covariance within
groups, but not affect the relative group mean values modelled
elsewhere in the design, then have 3 separate EVs. However, if your
groups are not perfectly age-matched, and you are hoping to partly
correct for that (it won't be perfect as the age effect won't be
exactly linear and additive!) then put all the ages into a single EV.
"
I am a little bit confused, do you still mean the same thing as Jeanette? Only that after demean across all subjects, split them into different groups and padd with zeros? Or do I misunderstood something here?
Cheers
2012/1/31 Stephen Smith
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Hi - it should be easy enough to edit the TBSS scripts $FSLDIR/bin/tbss* to change the standard space template. Also, you might well need to change the apparent voxel sizes in your original FA data to make TBSS work sensibly - e.g. changing the headers so they think the resolution is 1 or 2mm.
Cheers.
On 30 Jan 2012, at 06:56, dti mic wrote:
Dear FSL,
I am trying to run TBSS on some mouse data (simple t test between two groups of FA images). The resolution of FA image is about 0.1 mm^3. I understand since TBSS calls for MNI152 template by default, it can not be employed directly for mouse data. I tried search the archive but did not come up with very specific instructions to my question. Is there pipeline I can refer to? Your help will be highly appreciated!
micdtisever
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Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
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