AFNI Message Board

Dear AFNI users-

We are very pleased to announce that the new AFNI Message Board framework is up! Please join us at:

https://discuss.afni.nimh.nih.gov

Existing user accounts have been migrated, so returning users can login by requesting a password reset. New users can create accounts, as well, through a standard account creation process. Please note that these setup emails might initially go to spam folders (esp. for NIH users!), so please check those locations in the beginning.

The current Message Board discussion threads have been migrated to the new framework. The current Message Board will remain visible, but read-only, for a little while.

Sincerely, AFNI HQ

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rick reynolds
July 22, 2020 10:57AM
Hi Catherine,

With a fast event-related design, even the non-PPI regressors tend to look like noise, and certainly the PPI ones will. Also, if events are short, the PPI becomes more problematic, as it is very difficult to distinguish what happens only within the time of stimulus presentation when working with BOLD-convolved MRI data. In any case, plotting the PPI regressors will probably not fill you with confidence.

And yes, it is generally recommended to apply the gPPI regressors in a full model.

Note that there is a somewhat different but more complete example of PPI analysis here: AFNI_data6/FT_analysis/PPI. The cmd.ppi.2.make.regs script goes through creation of the gPPI regressors.

Again, working with short events makes this process even less stable than usual.

- rick
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Subject Author Posted

3dTfitter and gPPI modeling

Catherine Tallman July 03, 2020 09:27PM

Re: 3dTfitter and gPPI modeling

Catherine Tallman July 14, 2020 01:53PM

Re: 3dTfitter and gPPI modeling

rick reynolds July 22, 2020 10:57AM