Hi there,
After conducting a DODS analysis (One group, four factors, one
covariate), we were able to identify a region (LH pars opercularis)
whose mean thickness differed when two of the four factors interacted.
In order to further investigate the interaction, we obtained each
participant's mean thickness by drawing an ROI (using QDEC, which also
applied the mri_label2label function to map the new ROI to all the
participants).
However, when we extract the thickness data in this way, and then run
a glm on the ROI data (with the same four factors), the interaction is
no longer significant, and instead we observe a main effects of only
one of the factors.
Does anyone have an idea why there is such a disconnect between the
freesurfer output and the subsequent analysis (using glm in R)?
THANKS!!
clint
--
I remain...
Clinton L. Johns, Ph.D.
Research Scientist, Haskins Laboratories
300 George Street
New Haven CT 06511
speech: 203-865-6163 x240
fax: 203-865-8963
net: johns(a)haskins.yale.edu