Our group is running VBM in SPM5 on mean diffusivity data from DTI scans.
We are trying to perform an ANOVA using both a fixed factor and a random
factor. We have two groups of scans--scans from people who are relatives of
patients with schizophrenia, and scans from control families. We would like
to model the effect of family membership (sz family or control family) on
mean diffusivity measures. Because we have some relatives from the same
families, we would like to use family number as a random factor. The family
number measure is a unique identifier for each specific family, so there are
many different family numbers, and about 2 or 3 subjects to a family number.
Family membership is either 0 (for control families) or 1 (for family
members who are related to a schizophrenic patient).
I have been attempting to run the analysis in SPM5 using the Flexible
Factorial model in PET mode. I have used the family membership and family
number as factors, and I am covarying for sex, age, and CSF volume. I am
specifying family number as a dependent factor and family membership as
independent. However, I am somewhat confused as to how I should be
specifying the family numbers and family memberships, since these are not
covariates. I have been putting them in the Factor Matrix under the Specify
All Scans and factors submenu, but I'm not sure whether this is the correct
way to go about it. I've read up a bit on random effects analyses in fMRI
data, and have seen that it is possible to do a lower level contrast and
then a higher level t-test, but this will not work as my contrast is
specifically between subjects and not within subjects.
Any insight as to how I might perform this type of analysis on DTI data
would be greatly appreciated.
Thanks in advance!
Liberty Hamilton
UCLA Laboratory of NeuroImaging
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