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Hello,
I'm analyzing a large dataset using an LME model to examine longitudinal changes in brain structure that vary as a function of group (patients vs controls). Because some participants were scanned several years apart in early childhood, the intra-subject registration failed in the longitudinal processing stream. For this reason, my data were not initially processed using the longitudinal processing stream within Freesurfer. However, per this thread - https://www.mail-archive.com/freesurfer@nmr.mgh.harvard.edu/msg55847.html - I still plan to use the LME model. As I understand it, this model assumes that the longitudinal processing stream was conducted. Therefore, I have the following questions:
1. would the "base" (aka within-subject template) for each subject be = time point 1? 2. would the "long run" for each subject be = each subject's individual time points? 3. assuming #1 and 2 are correct, would I need to set my directory structure to match that used in the longitudinal processing stream? For example, if I have 2 time points for subject 1234, and they are initially labeled "1234.time1" and "1234.time2", then in order to run the LME model, I would create a copy of "1234.time1" and rename the copy as "1234" to indicate to the software that this should be used as the base. And, I would also need to rename "1234.time1" and "1234.time2" as "1234.time1.long.1234" and "1234.time2.long.1234" to indicate that these folders should be used as the longitudinal time points.
Does this seem appropriate?
Thanks in advance for your help, Lara
Lara Foland-Ross, Ph.D. Senior Research Associate and Imaging Lab Manager Center for Interdisciplinary Brain Sciences Research Stanford University School of Medicine 401 Quarry Road, Room 1356 Stanford, CA 94305-5795