Dear FS list, I have structural data from a learning study (pre&post-training scans, with 3 groups). Although the training was only one week, I'm guessing from an analysis point of view, this still qualifies as longitudinal. I want to check for
- the main within-subjects effect of time point (pre&post) - the main between-subjects effect of group (treatment A, treatment B, control), - the time x group interaction I intend to look at thickness, surface area, volume, and lGI. I read on the wiki<http://surfer.nmr.mgh.harvard.edu/fswiki/LongitudinalProcessing>that FS is currently not optimal for longitudinal analyses. I intend my FreeSurfer analysis to supplement a VBM analysis done in FSL. In case it is in fact a good idea to do this, my questions (not covered in the 'longitudinal' wiki page) are: 1) Can QDEC be used for such an analysis, and if so, what would be different as compared to a cross-sectional (no temporal/within factor) study? 2) Also, is the pre-processing stage any different? 3) In FSL, for longitudinal designs you do stats on images obtained as the difference between consecutive time points. Does this have to be done in FreeSurfer as well, and if so, is it done at the recon-all level or only at the stats (QDEC) level? Thanks! Tudor
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