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

History of AFNI updates  

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Oori
February 20, 2010 02:19AM
Hi Rick,

Could you explain the rational for why smoothing should be done before mean-normalization? Is there a model for the relation between noise magnitude and signal-baseline level that is driving this?
If I understand your point correctly, smoothing in the original value-range (i.e., before scaling) would help canceling out noise whose magnitude is baseline-independent. But does the scanner noise (and other types of noise) always have this property of baseline independence? Is noise magnitude never relative to a voxel's baseline? Intuitively, if noise magnitudes can/may be scaled relative to baseline, then the best way to cancel that noise out (e.g., in 2 nearby voxels that have very different baseline means) would be after baseline normalization. I haven't read any literature on this, so any pointers/experiences would be greatly appreciated.
Also, if this is an important point, might be good to add it to the soup_to_nuts walk-through. Till today I've never given the order of these two steps much thought, but it can clearly make a big difference.

Oori
Subject Author Posted

percent signal change before 3dDeconvolve

Anita Cservenka February 18, 2010 08:38PM

Re: percent signal change before 3dDeconvolve

rick reynolds February 19, 2010 11:42AM

Re: percent signal change before 3dDeconvolve

Anita Cservenka February 19, 2010 01:20PM

Re: percent signal change before 3dDeconvolve

Anita Cservenka February 19, 2010 04:19PM

Re: percent signal change before 3dDeconvolve

rick reynolds February 19, 2010 06:44PM

Re: percent signal change before 3dDeconvolve

Oori February 20, 2010 02:19AM

Re: percent signal change before 3dDeconvolve

rick reynolds February 22, 2010 09:56AM

Re: percent signal change before 3dDeconvolve

Oori February 22, 2010 10:52AM

Re: percent signal change before 3dDeconvolve

rick reynolds February 22, 2010 01:34PM

Re: percent signal change before 3dDeconvolve

Oori March 29, 2010 06:43AM

Re: percent signal change before 3dDeconvolve

rick reynolds March 31, 2010 09:39AM