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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Lee Friedman
May 04, 2006 08:01PM
Gang, Thanks.

What Worsley does in fmristat (and I think other packages do this as well)
is setup the HRF so that its integral is always 1.0.

Then then convolve this with the design.

According to Keith, the beta you get here is the beta for a very long
block regardless of how long the actual block is. In other words,
if the integral of the HRF is 1, then if the block is long enough, when
convovled with this HRF the peak will stabilize at 1.0. Therefore,
100*beta/intercept (assuming raw data) will give you percent change
for a very long block. This allows meaningful contrasts between short
blocks and long blocks.

Not sure I understand the math here, but two people have independently
stated this to me so i think this is the way to go.

Be interested in AFNI's reaction to this.

Lee
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Subject Author Posted

scaling regressors

Lee Friedman May 04, 2006 11:39AM

Re: scaling regressors

Gang Chen May 04, 2006 05:02PM

Re: scaling regressors

Lee Friedman May 04, 2006 08:01PM