Dear Freesurfer users I am trying to examine differences between 3 groups in surface thickness and volume over three time periods (pre-intervention, post-intervention, and 6-month followup). Previously, when only the first 2 time points were available, I followed the instructions for paired analysis detailed in https://surfer.nmr.mgh.harvard.edu/fswiki/PairedAnalysis. In the FSGD file, Group was the only Class. Now that I have 3 time points, I am trying to follow the instructions for repeated measures anova detailed in https://surfer.nmr.mgh.harvard.edu/fswiki/RepeatedMeasuresAnova. The FSGD file structure in this case is different, with each single participant having their own Class (i.e. in my case – 60 Classes for the 60 participants), and 2 variables contrasting the time points
GroupDescriptorFile 1 Class Subject1 Class Subject2 Class Subject3 Variables TP1-vs-TP2 TP1-vs-TP3 Input subject1-tp1 Subject1 1 1 Input subject1-tp2 Subject1 -1 0 Input subject1-tp3 Subject1 0 -1 Input subject2-tp1 Subject2 1 1 Input subject2-tp2 Subject2 -1 0 Input subject2-tp3 Subject2 0 -1 Input subject3-tp1 Subject3 1 1 Input subject3-tp2 Subject3 -1 0 Input subject3-tp3 Subject3 0 -1 In this case – the design matrix is (Sub1) (Sub2) (Sub3) (V1) (v2) 1 0 0 1 1 1 0 0 -1 0 1 0 0 0 -1 0 1 0 1 1 0 1 0 -1 0 0 1 0 0 -1 0 0 1 1 1 0 0 1 -1 0 0 0 1 0 -1
My question is whether and how can I incorporate participants' group (a between-subject variable) into this FSGD file? Should 3 additional Classes simply be added, one for each group, thereby making the new FSGD file as follows
GroupDescriptorFile 1 Class Group1 Class Group2 Class Group3 Class Subject1 Class Subject2 Class Subject3 Variables TP1-vs-TP2 TP1-vs-TP3 Input subject1-tp1 Subject1 Group3 1 1 Input subject1-tp2 Subject1 Group3 -1 0 Input subject1-tp3 Subject1 Group3 0 -1 Input subject2-tp1 Subject2 Group2 1 1 Input subject2-tp2 Subject2 Group2 -1 0 Input subject2-tp3 Subject2 Group2 0 -1 Input subject3-tp1 Subject3 Group3 1 1 Input subject3-tp2 Subject3 Group3 -1 0 Input subject3-tp3 Subject3 Group3 0 -1 and the matrix design as follows? (Group1)(Group2)(Group3)(Sub1)(Sub2) (Sub3) (V1) (v2) 0 0 1 1 0 0 1 1 0 0 1 1 0 0 -1 0 0 0 1 1 0 0 0 -1 0 1 0 0 1 0 1 1 0 1 0 0 1 0 -1 0 0 1 0 0 1 0 0 -1 0 0 1 0 0 1 1 1 0 0 1 0 0 1 -1 0 0 0 1 0 0 1 0 -1 Thank you Jonathan