Hi SPMers, I had a question about interpreting PPI results. The question is probably best illustrated with an example.
I have run my standard whole-brain analysis and identified two interesting peaks (A and B) from the group-level analysis. I then wanted to run two PPI analyses using each region as a seed. When I run a PPI using area A as my seed region, I find that area B displays a significant pyschophysiological interaction with area A. However, when I use area B as the seed, I do NOT find the same effect with A.
How does one interpret or explain this result? I found a post by Karl Friston (https://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=SPM;kwlgAQ;20100108150238%2B0000), which makes reference to this, but I still do not understand why this happens, or what it means.
Does anyone have some insight?
Best wishes,
Christopher Wilson
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