Dear SPMers
I'm trying to carry out a connectivity analysis using
Structural Equation Modeling. I'm hoping that someone
can advise me whether I'm performing my analysis
correctly. My method is the following:
1. realign, normalise and smooth my data in SPM5.
2. perform a random effects analysis to decide on
coordinates to use within my chosen brain regions.
3. perform a fixed effects analysis and extract data
from the coordinates chosen in the random effects
analysis.
4. for each subject, take an average of all the time
series within each region of interest to analyse.
5. for each brain region, perform principal component
analysis on a matrix containing the time series for
each subject.
6. take the first principal component as an input to
AMOS to perform structural equation modeling.
I seem to have a lot of variability in my data for
different subjects so my principal components don't
explain much of the variance (about 20%). Is this an
issue with scanning and variability which I can't do
anything about or am I doing something wrong?
Any advice would be greatly appreciated.
Many thanks
Nia
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