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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gang
July 25, 2014 09:15AM
> I ran 3dttest++ on a group of subjects and added BMI as a covariate. I am viewing the effect of BMI
> in the GUI and I have set a threshold, etc… > After "clusterize" I am given many significant clusters….
> but the clusters do not represent "activation", correct? They represent brain regions that are
> influenced by the covariate (BMI)?
>
> The "max intensity" of each cluster seemed very low (between 1 and -1) and it got me thinking about
> what it was that the max intensity of the covariate is actually reporting… Is it a correlation between
> the covariate scores and activation in the region?

Your model is

Y = b0 + b1 * BMI + error

The BMI effect b1 ("max intensity") is the BOLD response (e.g., percent signal change) when BMI increases by one unit. The clusters for b1 show the brain regions where the marginal or differential effect of BMI reaches a preset statistical significance level (e.g., p-value of 0.05).

Gang



Edited 1 time(s). Last edit at 07/25/2014 09:22AM by Gang.
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Subject Author Posted

3dttest++ Covariate max intensity of cluster meaning

adjacobson1 July 24, 2014 03:01PM

Re: 3dttest++ Covariate max intensity of cluster meaning

rick reynolds July 25, 2014 09:08AM

Re: 3dttest++ Covariate max intensity of cluster meaning

gang July 25, 2014 09:15AM

Re: 3dttest++ Covariate max intensity of cluster meaning

adjacobson1 July 28, 2014 11:32AM