Hi all,
I hope to get some advice during the DCM-PEB analysis if I don't want to concatenate multi sessions.
In my project, each subject has six sessions (runs) with identical scans (333 scans of TR = 2s). According to some studies, I should concatenate the sessions, then extract the time series from VOI. However, I am unsure how to add head motion parameters to the first-level GLM. Say the data was preprocessed session-wise, and each session has its head motion parameters, if the six sessions were combined into one session, which head motion parameters should I add?
So I plan to create a DCM for each session and do the PEB-of-PEBs for group analysis. I want to ask your advice if I think correctly as below:
Generally, I will have a 3-level design, first-level: DCM for each run, second-level: PEB for each subject, third-level: PEB for the group.
GCM_subject1 = [DCM_sbuject1run1, DCM_sbuject1run2, ..., DCM_sbuject1run6];
PEB_subject1 = spm_dcm_peb(GCM_subject1, X1); X1 contains six rows of 1, as the mean of this group.
GCM_all = [PEB_subject1,..., PEB_sbuject50]
PEB_all = [GCM_all, X2]; X2 contains one column of mean (i.e. 1) and other columns of covariates.
Do you think this approach is correct, or do you have other suggestions?
Best wishes,
Yang
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