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We have been struggling with constructing a PPI analysis which may be a little unorthodox (?), and are desperately in need of some guidance. We have an event-related experiment containing 5 contiguous sessions in each subject, and each of these sessions contains 136 scans (TR2.5). In each session, subjects perform 30 trials, each trial lasting 11s. Of these 30 trials, we have selective interest in 20 of them, and have corresponding psychological variables for the 20.
Our questions are:
1. For our defined region of interest, from what I understand for the PPI analysis, we have to select the SPM.mat file 5 times in order (corresponding to each of the 5 sessions) therefore saving the 5 respective VOI*.mat files, and then run the PPI algorithm 5 times. My first question is - is there any batch script which would enable us to run the analysis across all 5 sessions in toto?
2. In our design matrix, we have two event columns for each of the 5 sessions a) all trials (all 30 trials), and b) just the 20 trials of interest (which have the 20 corresponding psychological variables for. When I create my VOI and select the effects of interest contrast, it seems to select all 30 scans for that session, however I am only interested in the 20 scans corresponding to the 20 stimulus onset activities of the 20 trials. Is there any way I can selectively obtain these 20 and/or specify them, particularly since we have already done this in creating the original SPM.mat file using SOA values for these 20 trials.
3. How do I/ can I still perform a PPI analysis in this scenario?
4. If so, does anyone know of a batch script for PPI analysis across multiple subjects?
Many kind thanks in advance for any help offered,
Ninad