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Added from other thread as it has direct applicability to Nicole's question and possible needs for post-hoc explanation
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Hi, Alfonso.

Just to tag onto your response regarding the three-way Group X Condition x Condition interaction model and set-up in CONN.

As you know, we performed something similar for our patients and controls at two time points (baseline and follow-up) looking at a working memory load effect (2-back > 1-back). We found a region for this three-way group x time x working memory load contrast interaction, and we have compared that region with performance on a separate measure of cognition. The results were written up and sent off for review, and I received the following question from reviewer with respect to the CONN model and three-way interaction:

"Please provide justification for the (unusual) approach to test an interaction analysis on the first level. Which analyses were conducted on the second level? Two-sample t-test? How do you know what the results on the second level mean? There are many possibilities that can produce a significant interaction effect. Thus, you need to show post-hoc t-tests to disentangle interaction findings."

Any ideas on how to best address these questions? My understanding is that CONN is comparing the difference of time and condition factors between groups at the 2nd level. Are post-hoc t-tests even necessary to "disentangle interaction findings" when handled as t-tests of difference images?

Warm regards,
Jeff