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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ptaylor
January 21, 2019 05:14PM
Hi-

Yes, scaling is done voxelwise. For more information, particularly on the arguments for scaling, and a description of interpretability, please see the "units and scaling section" here:
[www.sciencedirect.com]
(or biorxiv version:
[www.biorxiv.org])
Actually, that whole article is relevant for your question(s).
See also section C-3 here:
[www.biorxiv.org]

The scaling is used to translate the unitless BOLD signal acquired by scanners to something interpretable as "BOLD percent signal change". And yes, that can certainly have negative values (--> a negative change from baseline). This is something that seems useful quantitatively, as well as for interpretation, and also for how the BOLD signal works (modulating response from blood oxygenation).

--pt
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Subject Author Posted

Scaling in the first level analysis

chaj January 21, 2019 05:02PM

Re: Scaling in the first level analysis

ptaylor January 21, 2019 05:14PM