I am working on an longitudinal analysis involving an fMRI paradigm with 3 visits. As a substantial number of patients had only two visits, I believe it is appropriate to use linear mixed effects analysis to be able to include those patients with missing data. My model fails and I am unsure why -
Does first-level analysis need to be conducted within AFNI? I am unsure if this is what is causing my problem. For example, I have previously analysed this data within FSL - am I able to use results from my first level analysis in FSL (e.g. cope files or t-statistics in standard space, for each subject/visit) as the inputs for 3dLME?
Otherwise, can you see any problem with my model specification below? Currently, it only contains 2 subjects, as I wanted to be sure it worked before including them all!
Be careful about the centering issue. If the group average of Time_dif varies across those three visits, you may have to center within each visit first before feeding those Time_dif values into the data table for 3dLME:
Thank you for your quick and very helpful reply!
As you suggested, I have changed the model and centred ‘Time_dif’ within each visit, before running the model on 10 subjects
However I am still running into problems and am unsure what I’m doing wrong -
I also checked the both the specification and table using the file tool, which showed no problems:
file_tool -infiles test.txt -test
test.txt has 0 bad characters
test.txt file type: UNIX
Any ideas what the remaining problem might be?
Thanks again,
Naomi
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