Hello,
I am running TBSS and randomise for the first time and
I wanted to make sure if I was doing everything right.
fsl experts please correct me. I have gone through the
archives on this topic and there were some questions
which I was not able to find answers to:
1. I have a single group of 9 subjects and I am
interested in testing for correlations of FA with fMRI
signal values. From what I have learnt from the
archives and the randomise manual, I would need to
define a design with 2 EVs - mean for the group i.e. 1
for all subjects and another EV for fMRI signal -
which is demeaned. By demeaning, you basically
calculate the average value over the group and to get
the demeaned values I would subtract this avg value
from the individual values, am I correct so far?
2. I also want to correct for age of the subjects.
This would be added as a separate confound matrix
rather than including in the design matrix right? So
this confound matrix would look something like - 2EVs
- one for the group mean and second EV containing age
values for each subject. I believe age needs to be
demeaned too? If I have more than one confound
variables, would I include all of them in a single
confound matrix or separate matrices are required?
3. From the archives, it looks like its recommended to
use the maxc_tstat output to make all the
interpretations. Randomise however produces max and
vox and raw tstat outputs. Is it valid to use these
outputs to interpret correlations?
4. Say EV1 is group mean and EV2 is fMRI signal, to
study positive correlations, I am using [0 1] contrast
and to study negative correlations I have the [0 -1]
contrast. Right?
5. This question might be more related when once I
have correctly finished these analyses. How would I
export the TBSS clusters as ROIs? Is there a tool for
that? Sorry I was able to find mention of this in the
archive, but did not find the tool for doing this.
Thanks for all the help and patience,
EJ
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