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If you used the 'trad' option in gPPI (not really gPPI then, just automated approach to doing it the same way as SPM), then you'd need to run separate models, but conditionA>conditionB+baseline not just A>baseline - unless you model baseline. If you used the 'cond' option, then you ran gPPI and you already have conditionA>baseline and conditionB>baseline. Both of these would be acceptable to plot. The units are arbitrary units (a.u.), but you can think of them as parameter estimates when your extracting them. Hope this helps. Let me know if you need more details. Best Regards, Donald McLaren ================= D.G. McLaren, Ph.D. Research Fellow, Department of Neurology, Massachusetts General Hospital and Harvard Medical School Postdoctoral Research Fellow, GRECC, Bedford VA Website: http://www.martinos.org/~mclaren Office: (773) 406-2464 ===================== This e-mail contains CONFIDENTIAL INFORMATION which may contain PROTECTED HEALTHCARE INFORMATION and may also be LEGALLY PRIVILEGED and which is intended only for the use of the individual or entity named above. If the reader of the e-mail is not the intended recipient or the employee or agent responsible for delivering it to the intended recipient, you are hereby notified that you are in possession of confidential and privileged information. Any unauthorized use, disclosure, copying or the taking of any action in reliance on the contents of this information is strictly prohibited and may be unlawful. If you have received this e-mail unintentionally, please immediately notify the sender via telephone at (773) 406-2464 or email. On Thu, Jul 12, 2012 at 7:45 AM, Ben Becker <[log in to unmask]> wrote: > Dear SPMers, > > I used gPPI to address between group differences in connectivity and found an interaction effect (for a contrast: (condition a > condition b). Now to further explore the interaction effect (that means to disentangle whether the interaction effect is driven by differences in condition a or b) is it valid to extract parameter estimates, %-signal change respectively from the underlying conditions? And does this mean I have to re-run the connectivity analysis for the contrasts condition a > implicit baseline and condition b > implicit baseline to generate the appropriate con-images for further extraction? > Thanks in advance & best regards > > Ben